The Transient High Energy Sky and Early Universe Surveyor (THESEUS)

Downloaded from orbit.dtu.dk on: Oct 10, 2021

Amati, L.; O'Brien, P.; Goetz, D.; Bozzo, E.; Tenzer, C.; Frontera, F.; Ghirlanda, G.; Labanti, C.; Osborne, J. P.; Stratta, G. Total number of authors: 212

Published in: Space Science Reviews

Publication date: 2021

Document Version Early version, also known as pre-print

Link back to DTU Orbit

Citation (APA): Amati, L., O'Brien, P., Goetz, D., Bozzo, E., Tenzer, C., Frontera, F., Ghirlanda, G., Labanti, C., Osborne, J. P., Stratta, G., Tanvir, N., Willingale, R., Attina, P., Campana, R., Castro-Tirado, A. J., Contini, C., Fuschino, F., Gomboc, A., Hudec, R., ... Zicha, J. (2021). The Transient High Energy Sky and Early Universe Surveyor (THESEUS). Manuscript submitted for publication. https://export.arxiv.org/abs/1710.04638v2

General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal

If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

my journal manuscript No. (will be inserted by the editor)

The Transient High Energy Sky and Early Universe Surveyor (THESEUS)

L. Amati · P. O’Brien · D. Gotz¨ · E. Bozzo · C. Tenzer · F. Frontera · G. Ghirlanda · C. Labanti · J. P. Osborne · G. Stratta · N. Tanvir · R. Willingale P. Attina · R. Campana · A.J. Castro-Tirado · C. Contini · F. Fuschino · A. Gomboc · R. Hudec · P. Orleanski · E. Renotte · T. Rodic · Z. Bagoly · A. Blain · P. Callanan · S. Covino · A. Ferrara · E. Le Floch · M. Marisaldi · S. Mereghetti · P. Rosati · A. Vacchi · P. D’Avanzo · P. Giommi · A. Gomboc · S. Piranomonte · L. Piro · V. Reglero · A. Rossi · A. Santangelo · R. Salvaterra · G. Tagliaferri · S. Vergani · S. Vinciguerra · M. Briggs · E. Campolongo · R. Ciolfi · V. Connaughton · B. Cordier · B. Morelli · M. Orlandini · C. Adami · A. Argan · J.-L. Atteia · N. Auricchio · L. Balazs · G. Baldazzi · S. Basa · R. Basak · P. Bellutti · M. G. Bernardini · G. Bertuccio · J. Braga · M. Branchesi · S. Brandt · E. Brocato · C. Budtz-Jorgensen · A. Bulgarelli · L. Burderi · J. Camp · S. Capozziello · J. Caruana · P. Casella · B. Cenko · P. Chardonnet · B. Ciardi · S. Colafrancesco · M. G. Dainotti · V. D’Elia · D. De Martino · M. De Pasquale · E. Del Monte · M. Della Valle · A. Drago · Y. Evangelista · M. Feroci · F. Finelli · M. Fiorini · J. Fynbo · A. Gal-Yam · B. Gendre · G. Ghisellini · A. Grado · C. Guidorzi · M. Hafizi · L. Hanlon · J. Hjorth · L. Izzo · L. Kiss · P. Kumar · I. Kuvvetli · M. Lavagna · T. Li · F. Longo · M. Lyutikov · U. Maio · E. Maiorano · P. Malcovati · D. Malesani · R. Margutti · A. Martin-Carrillo · N. Masetti · S. McBreen · R. Mignani · G. Morgante · C. Mundell · H. U. Nargaard-Nielsen · L. Nicastro · E. Palazzi · S. Paltani · F. Panessa · G. Pareschi · A. Pe’er · A. V. Penacchioni · E. Pian · E. Piedipalumbo · T. Piran · G. Rauw · M. Razzano · A. Read · L. Rezzolla · P. Romano · R. Ruffini · S. Savaglio · V. Sguera · P. Schady · W. Skidmore · L. Song · E. Stanway · R. Starling · M. Topinka · E. Troja · M. van Putten · E. Vanzella · S. Vercellone · C. Wilson-Hodge · D. Yonetoku · G. Zampa · N. Zampa · B. Zhang · B. B. Zhang · S. Zhang · S.-N. Zhang · A. Antonelli · F. Bianco · S. Boci · M. Boer · M. T. Botticella · O. Boulade · C. Butler · S. Campana · F. Capitanio · A. Celotti · Y. Chen · M. Colpi · A. Comastri · J.-G. Cuby · M. Dadina · A. De Luca · Y.-W. Dong · S. Ettori · P. Gandhi · E. Geza · J. Greiner · S. Guiriec · J. Harms · M. Hernanz · A. Hornstrup · I. Hutchinson · G. Israel · P. Jonker · Y. Kaneko · N. Kawai · K. Wiersema · S. Korpela · V. Lebrun · F. Lu · A. MacFadyen · G. Malaguti · L. Maraschi · A. Melandri · M. Modjaz · D. Morris · N. Omodei · A. Paizis · P. Pata´ · V. Petrosian · A. Rachevski · J. Rhoads · F. Ryde · L. Sabau-Graziati · N. Shigehiro · M. Sims · J. Soomin · D. Szecsi´ · Y. Urata · M. Uslenghi · L. Valenziano · G. Vianello · S. Vojtech · D. Watson · J. Zicha arXiv:1710.04638v2 [astro-ph.IM] 13 Oct 2017 Received: date / Accepted: date

L. Amati D. Gotz¨ INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, Italy IRFU/Departement´ d’Astrophysique, CEA, Universite´ Paris-Saclay, E-mail: [email protected] F-91191, Gif-sur-Yvette, France P. O’Brien E. Bozzo Department of Physics and Astronomy, University of Leicester, Department of Astronomy, University of Geneva, ch. d’Ecogia´ 16, Leicester LE1 7RH, UK CH-1290 Versoix, Switzerland 2 Amati et al.

Abstract THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Uni- verse and at providing a substantial advancement of multi- messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRBs and X-ray transients detection over a broad FOV (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeVs down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) follow-up with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the interstellar and intra-galactic medium up to redshift ∼10, signatures of Pop III stars, sources and physics of re-ionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravita- Fig. 1 Gamma-Ray Bursts in the cosmological context and the role tional radiation, which may be routinely detected in the late of THESEUS (adapted from a picture by the NASA/WMAP Science ’20s / early ’30s by next generation facilities like aLIGO/ Team). aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next gener- a fundamental synergy with the next-generation of gravita- ation of multi-wavelength observatories (e.g., LSST, ELT, tional wave and neutrino detectors (multi-messenger astro- SKA, CTA, ATHENA). physics), as well as the large electromagnetic (EM) facilities Keywords Gamma-ray: bursts · Cosmology: observations, of the next decade. dark ages, re-ionization, first stars The most critical THESEUS targets, i.e. GRBs, are unique and powerful tools for cosmology, especially because of their huge luminosities, mostly emitted in X- and gamma-rays, 1 Introduction their redshift (z) distribution (extending at least to z∼10), and their association with the explosive death of massive The Transient High Energy Sky and Early Universe Sur- stars. In particular, GRBs represent a unique tool to study veyor (THESEUS) is a space mission concept developed by the early Universe up to the re-ionization era. To date, there a large international collaboration in response to the calls is no consensus on the dominant sources of re-ionization, for M-class missions by the European Space Agency (ESA). and GRB progenitors and their hosts are very good repre- THESEUS is designed to vastly increase the discovery space sentatives of the massive stars and star-forming galaxies that of high energy transient phenomena over the entirety of cos- may have been responsible for this cosmic phase change. mic history (Fig. 1 and Fig. 2). Its driving science goals A statistical sample of high-z GRBs (between 30 and 80 at aim at finding answers to multiple fundamental questions of z>6, see Fig. 2) can provide fundamental information such modern cosmology and astrophysics, exploiting the mission as: measuring independently the cosmic star formation rate, unique capability to: a) explore the physical conditions of even beyond the limits of current and future galaxy surveys, the Early Universe (the cosmic dawn and re-ionization era) the number density and properties of low-mass galaxies, the by unveiling the Gamma-Ray Burst (GRB) population in the neutral hydrogen fraction, and the escape fraction of UV first billion years; b) perform an unprecedented deep mon- photons from high-z galaxies. Even JWST and ELTs sur- itoring of the soft X-ray transient Universe, thus providing veys, in the 2020s, will not be able to probe the faint end of the galaxy luminosity function (LF) at high redshifts (z>6- C. Tenzer Institut fur¨ Astronomie und Astrophysik, Abteilung Hochenergieastro- 8). The first generation of metal-free stars (the so-called Pop physik, Kepler Center for Astro and Particle Physics, Eberhard Karls III stars) and the second generation of massive, metal-poor Universitat,¨ Sand 1, D 72076 Tubingen,¨ Germany stars (the so-called Pop II stars) can result in powerful GRBs (see, e.g., Mesz´ aros´ and Rees 2010) that thus offer a direct Full author list and affiliations are provided at the end of the route to identify such elusive objects (even JWST will not be paper. able to detect them directly) and study the galaxies in which THESEUS 3

Fig. 2 The yearly cumulative distribution of GRBs with redshift determination as a function of the redshift for Swift and THESEUS (see details in Sect. 2.1). We note that these predictions are conservative in so far as they reproduce the current GRB rate as a function of redshift. However, 53 with our sensitivity, we can detect a GRB of Eiso ∼ 10 erg (corresponding to the median of the GRB radiated energy distribution) up to z=12. Indeed, our poor knowledge of the GRB rate-SFR connection does not preclude the existence of a sizable number of GRBs at such high redshifts, in keeping with recent models of Pop III stars. they are hosted. Even indirectly, the role of Pop III stars in tion rate and characterization of sub-energetic GRBs and enriching the first galaxies with metals can be studied by X-Ray Flashes. Monitoring observations of bright and faint looking to the absorption features of Pop II GRBs blowing X-ray objects will be routinely carried out, and a dramatic out in a medium enriched by the first Pop III supernovae (Ma increase in the rate of discovery of high-energy transient et al. 2017). Moreover, both Pop III and massive Pop II stars sources over the whole sky is certainly expected, includ- may have contributed to the reionization of the Universe due ing supernova shock break-outs, black hole tidal disruption to their intensive ionizing radiation (Yoon et al. 2012; Szecsi´ events, and magnetar flares. et al. 2015), thus detecting their final explosion will help us The primary scientific goals of the mission thus address better understand our cosmic history. the Early Universe ESA Cosmic Vision theme “How did the Besides high-redshift GRBs, THESEUS will serendipi- Universe originate and what is it made of?” and, specifically, tously detect and localize during regular observations a large the sub-themes: 4.1) Early Universe, 4.2) The Universe tak- number of X-ray transients and variable sources (Fig. 3 and ing shape, and 4.3) The evolving violent Universe. They Fig. 4), collecting also prompt follow-up data in the IR (see also have a relevant impact on the 3.2 themes: “The Grav- Tables 1 and 2). These observations will provide a wealth of itational Wave Universe” and “The Hot and Energetic Uni- unique science opportunities, by revealing the violent Uni- verse”. In addition, THESEUS will also automatically en- verse as it occurs in real-time, exploiting an all-sky X-ray able excellent observatory science opportunities, thus allow- monitoring of extraordinary grasp and sensitivity carried out ing a strong community involvement. It is worth remarking at high cadence. THESEUS will be able to locate and iden- that THESEUS will have survey capabilities for high-energy tify the electromagnetic counterparts to sources of gravita- transient phenomena complementary to the Large Synoptic tional radiation and neutrinos, which will be routinely de- Survey Telescope (LSST) in the optical. Their joint avail- tected in the late ’20s / early ’30s by next generation fa- ability at the end of the next decade would enable a remark- cilities like aLIGO/ aVirgo, eLISA, ET, and Km3NET. In able scientific synergy between them. addition, the provision of a high cadence soft X-ray moni- The THESEUS scientific goals related to the full explo- toring capability in the 2020s together with a 0.7 m IRT in ration of the early Universe requires requires the detection orbit will enable a strong synergy with transient phenomena of many tens of GRBs from the first billion years (about observed with the large facilities that will be operating in 30-80), around ten times the number currently known at a the EM domain (e.g., ELT, SKA, CTA, JWST, ATHENA). redshift z>6 (Fig. 2). This is well beyond the capabilities of The large number of GRBs found in the survey will per- current and near future GRB detectors (Swift/BAT, the most mit unprecedented insights in the physics and progenitors of sensitive one, has detected only very few GRBs above z=6 in these events and their connection with peculiar core-collapse 10 yrs). As supported by intensive simulations performed by SNe. THESEUS will also substantially increase the detec- us and other works in the literature (see, e.g., Ghirlanda et al. 4 Amati et al.

Fig. 3 By the end of the ’20s, if Einstein Telescope will be a single detector, almost no directional information will be available for GW sources, and a GRB-localising satellite will be essential to discover EM counterparts. If multiple third-generation detectors will be available, the typical localization uncertainties will be comparable to the aLIGO ones. The plot shows the SXI ﬁeld of view (∼110×30 deg2) superimposed on the probability skymap of GW151226 observed by aLIGO.

Fig. 4 Sensitivity of the SXI (black curves) and XGIS (red) vs. integration time (only for the instrument central spot). The solid curves assume a source column density of 5×1020 cm−2 (i.e., well out of the Galactic plane and very little intrinsic absorption). The dotted curves assume a source column density of 1022 cm−2 (significant intrinsic absorption). The black dots are the peak fluxes for Swift BAT GRBs plotted against T90/2. The flux in the soft band 0.3-10 keV was estimated using the T90 BAT spectral fit including the absorption from the XRT spectral fit. The red dots are those GRBs for which T90/2 is less than 1 s. The green dots are the initial fluxes and times since trigger at the start of the Swift XRT GRB light-curves. The horizontal lines indicate the duration of the first time bin in the XRT light-curve. The various shaded regions illustrate variability and flux regions for different types of transients and variable sources.

2015), the required substantial increase of high-z GRBs im- on-board spectroscopy and redshift measurement, as well as plies both an increase of ∼1 order of magnitude in sensitivity optical and IR follow-up observations. and an extension of the detector passband down to the softer X-rays (0.5-1 keV). Such capabilities must be provided over The required THESEUS performances can be best ob- a broad ﬁeld of view (∼1 sr) with a source location accuracy tained by including in the payload a monitor based on the <2 arcmin, in order to allow eﬃcient counterpart detection, lobster-eye telescope technology, capable of focusing soft X-rays in the 0.3-6 keV energy band over a large FOV. Such instrumentation has been under development for several years THESEUS 5

Fig. 5 THESEUS Satellite Baseline Configuration and Instrument suite accommodation. at the University of Leicester, has a high TRL level (e.g., broad energy band, thus getting fundamental insights into BepiColombo, SVOM) and can perform all-sky monitor- their physics. In summary, the foreseen payload of THE- ing in the soft X-rays with an unprecedented combination SEUS includes the following instrumentation: of FOV, source location accuracy (<1-2 arcmin) and sensi- – Soft X-ray Imager (SXI, 0.3-6 keV): a set of 4 lobster- tivity. An on-board infrared telescope of the 0.5-1 m class eye telescopes units, covering a total FOV of ∼1 sr with is also needed, together with the fast slewing capability of source location accuracy <1-2 arcmin; the spacecraft (e.g., several degrees per minute), in order to – InfraRed Telescope (IRT, 0.7-1.8 µm): a 0.7 m class IR provide prompt identification of the GRB optical/IR coun- telescope with 10×10 arcmin FOV, for fast response, terpart, refinement of the position down to ∼arcsec preci- with both imaging and spectroscopy capabilities; sion (thus enabling follow-up with the largest ground and – X-Gamma ray Imaging Spectrometer (XGIS, 2 keV-20 MeV): space observatories), on-board redshift determination and a set of coded-mask cameras using monolithic X-gamma spectroscopy of the counterpart and of the host galaxy. This ray detectors based on bars of Silicon diodes coupled capability will add considerably to the science value of ATHENA with CsI crystal scintillator, granting a ∼1.5 sr FOV, a by providing a sample of known high-redshift bursts with source location accuracy of ∼5 arcmin in 2-30 keV and which it will be able to sample the intervening WHIM. an unprecedently broad energy band. The telescope may also be used for multiple observatory In Fig. 5 we show a sketch of the THESEUS baseline and survey science goals. Finally, the inclusion in the pay- configuration and instrument suite accommodation as pro- load of a broad field of view hard X-ray detection system posed for ESA/M5. The mission profile also includes: an on- covering the same monitoring FOV as the lobster-eye tele- board data handling units (DHUs) system capable of detect- scopes and extending the energy band from few keV up to ing, identifying and localizing likely transients in the SXI several MeV will increase significantly the capabilities of and XGIS FOV; the capability of promptly (within a few the mission. As the lobster-eye telescopes can be triggered tens of seconds at most) transmitting to ground the trigger by many classes of transient phenomena (e.g., flare stars, X- time and position of GRBs (and other transients of interest); ray bursts, etc), the hard X-ray detection system provides an a spacecraft slewing capability of ∼5-10 deg/min. The base- efficient means to identify real GRBs and detect other tran- line launcher/orbit configuration is a launch with Vega-C to sient sources (e.g., soft Gamma-repeaters). The joint data a low inclination low Earth orbit (LEO, ∼600 km, <5 deg), from the three instruments will characterize transients in which has the unique advantages of granting a low and sta- terms of luminosity, spectra and timing properties over a ble background level in the high-energy instruments, allow- 6 Amati et al. ing the exploitation of the Earth’s magnetic field for space- early ’30s by next generation facilities like aLIGO/ craft fast slewing and facilitating the prompt transmission of aVirgo, eLISA, ET, or Km3NET; transient triggers and positions to the ground. – Provide real-time triggers and accurate (∼1 arcmin This article provides an extensive review of the THE- within a few seconds; ∼1 arcsec within a few min- SEUS science case, scientific requirements, proposed instru- utes) locations of (long/short) GRBs and high-energy ments, mission profile, expected performances, as proposed transients for follow-up with next-generation optical- in response to the ESA Call for M5 mission within the Cos- NIR (ELT, JWST if still operating), radio (SKA), X- mic Vision Programme. The current THESEUS collabora- rays (ATHENA), and TeV (CTA) telescopes; tion involves more than 100 scientists from all over the world. – Provide a fundamental step forward in the compre- The payload consortium is composed by several European hension of the physics of various classes of Galac- countries, with a main role of Italy, UK, France, Germany, tic and extra-Galactic transients, e.g.: tidal disruption and Switzerland. Significant contributions are planned by events (TDE), magnetars/SGRs, SN shock break-outs, Spain, Belgium, Czech Republic, and Poland. Additional Soft X-ray Transients, thermonuclear bursts from ac- contributions have been proposed by Ireland, Hungary, Slove- creting neutron stars, Novae, dwarf novae, stellar flares, nia, and Albania. International contributions are being dis- AGNs and Blazars; cussed in several extra-European countries, including USA, – Fill the present gap in the discovery space of new Brazil, and China (already involved in the mission study). classes of high-energy transient events, thus provid- OHB Italia and GP Advanced Projects (Italy) kindly con- ing unexpected phenomena and discoveries. tributed to the study and definition of the technical aspects of the THESEUS mission concept. Below, we detail the THESEUS science case and de- scribe the rich observatory science that will come out as a result of meeting the primary mission requirements. We show 2 Science case that the unique capabilities of this mission will enlarge several research fields, and will be beneficial for multiple sci- The THESEUS specific science objectives can be summa- entific communities. rized as follows:

A. Explore the physical conditions of the Early Universe (cosmic dawn and reionization era) by unveiling a com- 2.1 Exploring the Early Universe with Gamma-Ray Bursts plete census of the GRB population in the first billion years. This will be achieved by: A major goal of contemporary astrophysics and cosmology – Performing studies of the global star formation his- is to achieve a broad understanding of the formation of the tory of the Universe up to z∼10 and possibly beyond first collapsed structures (Pop III and early Pop II stars, black with an unprecedented sensitivity for the detection holes and galaxies) during the first billion years in the life of of GRBs at high redshifts; the universe. This is intimately connected to the reioniza- – Detecting and studying the primordial (Pop III) and tion of the IGM and build-up of global metallicity. The lat- subsequent (Pop II) star populations: when did the ter is very poorly constrained, and even in the JWST era will earliest stars form and how did they influence their rely on crude emission line diagnostics for only the bright- environments? est galaxies. Regarding reionization, measurements of the – Investigating the re-ionization epoch by determining Thomson scattering optical depth to the microwave back- the physical properties of the the interstellar medium ground by the Planck satellite now suggest it substantially (ISM) and the intergalactic medium (IGM) up to z ∼8- occurred in the redshift range z∼7.8-8.8 (see, e.g., Planck 10: how did re-ionization proceed as a function of Collaboration et al. 2016), whereas the observations of the environment, and was radiation from massive stars Gunn-Peterson trough in the spectra of distant quasars and its primary driver? How did cosmic chemical evolu- galaxies indicate it was largely finished by z∼6.5 (see, e.g., tion proceed as a function of time and environment? Caruana et al. 2012, 2014; Schenker et al. 2014). Statisti- – Investigating the properties of the early galaxies and cal measurements of the fluctuations in the redshifted 21 cm determining their star formation properties in the re- line of neutral hydrogen by experiments such as LOFAR and ionization era. SKA are expected to soon provide further constraints on the B. Perform an unprecedented deep monitoring of the X-ray time history (see, e.g., Patil et al. 2014). The central ques- transient Universe in order to: tion, however, remains whether it was predominantly radi- – Locate and identify the electromagnetic counterparts ation from massive stars that both brought about and sus- to sources of gravitational radiation and neutrinos, tained this phase change, or whether more exotic mecha- which may be routinely detected in the late ’20s / nisms must be sought. THESEUS 7

gas of the galaxy (through follow-up observations). There- fore, we will be able to probe star formation eﬃciency, escape fraction, metal enrichment and galaxy evolution during, and even preceding, the epoch of reionization. This unique contribution will be one of the most important that THE- SEUS will provide.

Global star formation from GRB rate as a function of redshift Long-duration GRBs are produced by massive stars, and so track star formation, and in particular the populations of UV-bright stars responsible for the bulk of ionizing radiation production. Although there is evidence at low redshift that GRBs are disfavoured in high metallicity environments, Fig. 6 Redshift distribution of GRBs (credits Berger, Harvard/CfA). since high redshift star formation is predominantly at low metallicity (see, e.g., Salvaterra et al. 2013; Perley et al. 2016; Vergani et al. 2017) it is likely that the GRB rate to Solving this problem largely splits into two subsidiary massive star formation rate ratio is approximately constant issues: how much massive star formation was occurring as beyond z '3. Thus simply establishing the GRB N(z), and a function of redshift? And, on average, what proportion of accounting for the instrumental selection function, provides the ionizing radiation produced by these massive stars man- a direct tracer of the global star formation rate density as a ages to escape from the immediate environs of their host function of cosmic time (Fig. 6). How selection bias is taken galaxies? An answer to the former question can be extrap- into account is relevant for a correct evaluation of the star olated based on observed candidate z >7 galaxies found in formation rate (Petrosian et al. 2015; Dainotti et al. 2015). Hubble Space Telescope (HST) deep fields, but there are two Analyses of this sort have consistently pointed to a higher very significant uncertainties. The first is the completeness SFR density at redshifts z > 6 than traditionally inferred and cleanliness of the photometric redshift samples at z >7, from UV rest-frame galaxy studies (see Fig. 7 left), which while the second is the poorly constrained form and faint- rely on counting star-forming galaxies and attempting to ac- 8 end behaviour of the galaxy LF (at stellar masses .10 M ), count for galaxies below the detection threshold. Although especially since galaxies below the HST detection limit very this discrepancy has been alleviated by the growing realisa- likely dominate the star formation budget. Even though some tion of the extremely steep faint-end slope of the galaxy LF constraints on fainter galaxies can be obtained through ob- at z > 6, it still appears that this steep slope must continue to servations of lensing clusters (see, e.g., Atek et al. 2015; very faint magnitudes, MAB ' −11, in order to provide con- Vanzella et al. 2017a,b), which will be improved further by sistency with GRB counts and indeed to achieve reionization JWST, simulations suggest star formation was still likely (something that can only be quantified via a full census of occurring in considerably fainter systems (Liu et al. 2016). the GRB population). The second question concerns the Lyman continuum escape fraction and it is even more difficult to be answered, since this parameter cannot be determined directly at high red- The high-z galaxy luminosity function shifts and lower redshift studies have generally found rather The shape and normalisation of the high-redshift galaxy lu- low values of the escape fraction fesc of only a few per- minosity function is a key issue for understanding reioniza- cent (Grazian et al. 2017). This is likely insufficient to drive tion since, to the depth achieved in the Hubble Ultra-deep reionization unless fesc increases significantly at early times Field (HUDF), it appears that the faint-end of the LF at and/or for smaller galaxies (see, e.g., Robertson et al. 2013). z > 6 approaches a power-law of slope α = 2. Thus the Recently, an analysis of a sample of GRB afterglow spec- value of the total luminosity integral depends sensitively on tra in the range 1.6 < z < 6.7 found a 98% upper limit to the choice of the low-luminosity cut-off (and indeed the as- the average ionizing escape fraction of 1.5% (Tanvir et al. sumption of continued power-law form for the LF). By con- submitted). ducting deep searches for the hosts of GRBs at high-z we These questions may be answered by the help of GRBs can directly estimate the ratio of star formation occurring in and their host galaxies. With the help of THESEUS, we can detectable and undetectable galaxies, with the sole assump- combine information on the cold/warm ISM gas of faint star tion that the GRB-rate is proportional to the star formation forming galaxies (through the afterglow spectroscopy) with rate (see Fig. 7 left). Although currently limited by small- that on the emission properties of the continuum and ionised number statistics, the early application of this technique has 8 Amati et al. confirmed that the majority of the star formation at z & 6 oc- far. Thus, our theoretical understanding of the structure and curred in galaxies below the effective detection limit of HST evolution, as well as the nature of the final explosion, of the (Tanvir et al. 2012; McGuire et al. 2016). Since the exact po- first stars still relies on many assumptions. Stellar evolution sition and redshift of the galaxy is known via the GRB after- predicts that long GRBs may be expected from fast rotating, glow, follow-up observations are more efficient than equiv- single Pop III stars with an initial mass of 10-80 M (Yoon alent deep field searches for Lyman-break galaxies. et al. 2012). Above this mass limit, a Pop III star may explode due to pair-instability as a Superluminous Supernova, The build-up of metals, molecules and dust or not explode at all, falling back directly to a black hole Bright GRB afterglows with their intrinsic power-law spec- (Heger et al. 2003). When a Pop III star explodes it changes tra provide ideal backlights for measuring not only the hy- the chemical composition of its environment, from which drogen column, but also obtaining exquisite abundances and the second stars are formed. These ideas must be examined. gas kinematics probing to the hearts of their host galaxies Also, having a full census of GRBs with Pop III progenitors (see Fig. 7 right and, e.g., Hartoog et al. 2015). Further, the has the potential to provide an unprecedented enhancement imprint of the local dust law, and in some cases observa- of our knowledge of stellar evolution. tion of H2 molecular absorption, provides further detailed The same is true for the subsequent generations of stars evidence of the state of the host ISM (see, e.g., Friis et al. in the early Universe: low-metallicity massive stars, or Pop 2015). They can thus be used to monitor cosmic metal en- II stars, have been simulated using our best theoretical ap- richment and chemical evolution to early times, and search proach, but observational evidences are needed to confirm for evidence of the nucleosynthetic products of even earlier the theory (Szecsi´ et al. 2015). In particular, one of the most generations of stars. In the late 2020s, taking advantage of promising evolutionary channels leading to fast rotating he- the availability of 30 m class ground-based telescopes (and lium stars (the so-called “chemically homogeneous evolu- definitely ATHENA), superb abundance determinations will tion”) still needs to be tested observationally. These fast ro- be possible through simultaneous measurement of metal ab- tating helium stars at low metallicity (or TWUIN stars; Szecsi´ sorption lines and modelling the red-wing of Ly-alpha to et al. 2015) are predicted to be progenitors of long GRBs if determine host HI column density, potentially even many single (Yoon et al. 2006) or progenitors of short GRBs if in days after the burst (see Fig. 9). We emphasize that using a close binary system (Marchant et al. 2017; Szecsi´ 2017). the THESEUS on-board NIR spectroscopy capabilities (see The detection of GRBs with Pop III or Pop II progenitors Sect. 4 and Fig. 37) will provide the redshifts and luminos- provides important insights on stellar astrophysics. ity measurements that are essential to optimise the time- Both Pop III and massive Pop II stars are expected to critical follow-up observations using the highly expensive emit a large number of ionizing photons and thus to con- next-generation facilities, allowing us to select the highest tribute to the ionization of their surroundings. Despite being priority targets and use the most appropriate telescope and potentially crucial in understanding cosmic reionization, the instrument. predictions of the models are still weighted with uncertainties due to scarce observational constraints on metal-free and Topology of reionization metal-poor massive stars. We also expect that interpreting It is expected that reionization should proceed in a patchy the data output of THESEUS will bring together scientists way, with ionized bubbles being created first around the high- working on the so-far mostly unrelated fields of reionization est density peaks where the first galaxies occur, expanding history and stellar evolution. and ultimately filling the whole IGM. The topology of the In addition to possible evidence for population III chem- growing network of ionized regions reflects the character ical enrichment, it has been argued that Pop III stars may of the early structure formation and the ionizing radiation also produce collapsar-like jetted explosions, which are likely field. With high-S/N afterglow spectroscopy, the Ly-alpha to be of longer duration than typical long-GRBs, and may be red damping wing can be decomposed into contributions detected through surveys with longer dwell times (Mesz´ aros´ due to the host galaxy and the IGM. The latter provides the and Rees 2010). To date, no direct evidence of this connec- hydrogen neutral fraction and so measures the progress of tion has been observationally established. The multiwave- reionization local to the burst. With samples of several tens length properties of GRBs with a Pop-III progenitor are only of GRBs at z & 7 − 8, we can begin to statistically investi- predicted on the expected large masses and zero metallicity gate the average and variance of the reionization process as of these stars. Even the detection of a single GRB from a a function of redshift (see, e.g., McQuinn et al. 2008). Pop III progenitor would put fundamental constraints on the Population III stars unknown properties of the first stars. The first stars in the Universe are supposed to be very massive and completely metal-free. However, no direct detec- The role of THESEUS tion of such objects, called Pop III stars, has been made so Our detailed simulations indicate that THESEUS will de- THESEUS 9

Fig. 7 Left: Star Formation Rate density as a function of redshift from Kistler et al. (2013). Low-z data (circles) are from Hopkins and Beacom (2006), while diamonds are from Kistler et al. (2013). The open squares show the result of integrating the Lyman break galaxy UV luminosity functions down to the lowest measured magnitude in optical, while the solid squares represent the results obtained by stopping the integration at an optical magnitude of -10. The Salpeter initial mass function (IMF) is assumed in all cases. The plot also show with dotted lines the criticalρ ˙∗ from Madau et al. (1999) for a ratio between the clumping factor and the escape fraction of 40, 30, and 20 (top to bottom). Right: Absorption-line based metallicities [M/H] as a function of redshift of Damped Lyman-α absorbers, for GRB-DLAs (blue symbols) and emission line metallicities for GRB hosts (red symbols, adapted from Sparre et al. 2014). GRBs are essential to probe the evolution of ISM metallicities in the first billion years of cosmic history. tect between 30 and 80 GRBs at z > 6 over a three year WHIM); this requires about 10 bright GRBs per year. (2) mission, with between 10 and 25 of these at z > 8 (and sev- Probe the first generation of stars by finding high redshift eral at z > 10). The on-board follow-up capability means GRB; this requires about 5 high-redshift GRBs per year. that redshifts are estimated for the large majority of these, THESEUS will enable ATHENA to achieve these goals by and powerful next generation ground- and space-based tele- greatly increasing the rate of GRBs found per year with good scopes available in this era will lead to extremely deep host localisations and redshifts. The X-ray band of the THESEUS searches and high-S/N afterglow spectroscopy for many of SXI (see Sect. 4.1) will find a greater proportion of high- them (e.g., using JWST, if still operating, ELT, WFIRST, redshift GRBs than previous missions. Hence THESEUS EUCLID, ATHENA, etc.). To illustrate the potential of such will: (1) localise bright GRBs with sufficient accuracy us- a sample, we simulate in Fig. 8 the precision in constraining ing the SXI to enable a rapid repointing of the ATHENA the product of the UV luminosity density and average es- X-IFU for X-ray spectroscopy of the WHIM, and (2) find cape fraction, ρUV fesc, that would be obtained with 25 GRBs high-redshift GRBs using the SXI and XGIS and accurately at 7 < z < 9 having high-S/N afterglow spectroscopy and localising them using the IRT for redshift determination on- (3 hr) JWST depth host searches (for definiteness the ρUV board and on the ground to provide reliable high-redshift axis corresponds to z = 8). This will provide a much clearer targets for ATHENA. Many of the other transients found by answer to the question of whether stars were the dominant THESEUS, such as tidal disruption events and flaring bina- contributors to reionization. In addition, this sample will al- ries, will also be high-value targets for ATHENA. low us to map abundance patterns across the whole range of the star forming galaxies in the early universe, providing multiple windows on the nature of the first generations of 2.2 Gravitational wave sources and multi-messenger stars. astrophysics

The great value of THESEUS to ATHENA The launch of THESEUS will coincide with a golden era of As an example of the great relevance of THESEUS in the multi-messenger astronomy. With the ﬁrst detection of grav- context of the next generation large facilities (e.g., SKA, itational waves (GWs) by Advanced detectors (Abbott et al. CTA, ELT, ATHENA), we highlight here the THESEUS syn- 2016b,a), a new window on the Universe has been opened. ergy with ATHENA. Two of the primary science goals for By the end of the present decade, the sky will be routinely ATHENA are: (1) Locate the missing baryons in the Uni- monitored by a network of second generation GW detectors, verse by probing the Warm Hot Intergalactic Medium (the an ensemble of Michelson-type interferometers, composed 10 Amati et al.

Fig. 9 Simulated ELT spectrum of a GRB at z=8.2 as discovered by THESEUS. The S/N provides exquisite abundance determinations Fig. 8 The UV luminosity density from stars at z ' 8 and aver- from metal absorption lines, while fitting the Ly-a damping wing si- age escape fraction h f i are insufficient to sustain reionization un- esc multaneously fixes the IGM neutral fraction and the host HI column less the galaxy luminosity function steepens to magnitudes fainter than density, as illustrated by the two extreme models: a pure 100% neu- M = −13 (grey hatched region), and/or h f i is much higher than UV esc tral IGM (green) and best-fit host absorption with a fully ionized IGM that typically found at z ' 3 (grey shaded region). Even in the late (red). 2020s, h fesci at these redshifts will be largely unconstrained by direct observations. The green contours show the 1 and 2-σ expectations for a sample of 25 GRBs at z ' 7 − 9 for which deep spectroscopy provides the host neutral column and deep imaging constrains the fraction of star formation occurring in hosts below the JWST limit (Robert- THESEUS/SXI FoV (see Fig. 10). In parallel to these ad- son et al. 2013). The input parameters were log10(ρUV) = 26.44 and vancements, IceCube and KM3nNeT and the advent of 10 h fesci = 0.23, close to the (red) borderline for maintaining reionization km3 detectors (e.g. IceCube-Gen2, IceCube-Gen2 Collab- by stars. oration et al. (2014)) will likely revolutionize neutrino astrophysics. Neutrino detectors can localize to an accuracy of better than a few sq. degrees but within a smaller vol- by the two Advanced LIGO (aLIGO) detectors in the USA ume of the Universe (see, e.g., Santander 2016, and ref- and by Advanced Virgo (aVirgo) in Italy, plus ILIGO in In- erences therein). In order to maximize the science return dia and KAGRA in Japan joining later within a few years. of the multi-messenger investigation it is essential to have By the first years of 2030, more sensitive third generation an in-orbit trigger and search facility that can either detect GW detectors, such as the Einstein Telescope (ET) and Cos- an EM signal simultaneous with a GW/neutrino event or mic Explorer, are planned to be operative and to provide an rapidly observe with good sensitivity the large error boxes increase of roughly one order of magnitude in sensitivity. provided by the GW and neutrino facilities following a trig- Several of the most powerful transient sources of GWs ger. These combined requirements are uniquely fulfilled by predicted by general relativity, e.g. binary neutron star (NS- THESEUS, which is able to trigger using XGIS or SXI and NS) or NS-black hole (BH) mergers (with likely detection observe a very large fraction of the GW/neutrino error boxes rate of ∼50 per year by the LIGO-Virgo network at design within an orbit due to the large grasp of the SXI instru- sensitivity; Abadie et al. 2010a), are expected to produce ment (if compared to current generation X-ray facilities such bright electromagnetic (EM) signals across the entire EM as Swift, THESEUS/SXI has a grasp of ∼150 times that spectrum and in particular in the X-ray and gamma-ray en- of Swift/XRT). For events triggered on-board with XGIS ergy bands, as well as neutrinos. GW detectors have rel- or SXI, GW searches can also be carried on the resultant atively poor sky localization capabilities mainly based on known sky locations with lower GW detector signal-to-noise triangulation methods. With three detectors ∼80 square de- thresholds and hence an increased search distance. In 2020s grees are achieved; this sky localization accuracy may also synergies with the future facilities like JWST, WFIRST, Ein- apply for the third-generation GW detectors by 2030+. By stein Probe, ATHENA, ELT, TMT, GMT, SKA, CTA, zPTF, 2020+ the second-generation network will count three up and LSST telescopes would leverage significant added value, to five GW detectors and sky localization will improve to extending the multi-messenger observations across the whole ∼1-10 sq. degrees or even less (Klimenko et al. 2011). Such EM spectrum. The detection of EM counterparts of GW (or localization uncertainties will be completely covered by the possibly neutrino) signals will enable a multitude of science THESEUS 11

the next years will likely confirm this scenario by simultaneous detections of CBC-GWs temporally and spatially consistent with short GRBs. Second-generation GW network can detect NS-NS and NS-BH systems up to 0.4-0.9 Gpc (Abadie et al. 2010a). Since the estimated rate density of detected short GRBs is 1-10 Gpc−3 yr−1 (see Wanderman and Piran 2015; Ghirlanda et al. 2016, and references therein) the expected annual rate of on-axis (i.e. face-on) short GRBs with GW counterpart before the third generation detectors (see below) is rather low, of the order of a few per year or less. However, in Fig. 10 The plot shows the SXI field of view (∼110×30 deg2) superimposed on a simulated probability skymap of a merger NS-NS system a more realistic jet scenario, e.g. a structured jet scenario, observed by aLIGO and advanced Virgo (Singer et al. 2016). The SXI prompt GRB photon flux F can vary with observer view- coverage contains nearly 100% of the total probability. ing angle Θobs. According to Pescalli et al. (2016), F ∼ −s Fcore(Θobs/Θ jet) with s > 2, where Fcore is the typical on- axis flux of a short GRB (see Fig. 11). Assuming F ∼10 programmes (see, e.g., Bloom et al. 2009; Phinney 2009) core ph cm−2 s−1 (e.g. Narayana Bhat et al. 2016), since short by allowing for parameter constraints that the GW/neutrino GRBs have a median redshift of z ∼ 0.5 (Berger 2014), at observations alone cannot fully provide. For example, find- a distance of ∼ 400 Mpc F would be ∼ 103 ph cm−2 ing a GW/neutrino source EM counterpart in X-rays with core s−1, thus even assuming a steep dependence of F from Θ THESEUS/SXI will allow to localize the source with an ac- view (e.g. s = 6) a nearby short GRB can be detected off-axis curacy good enough for optical follow-up and hence to pos- with THESEUS/XGIS up to 5Θ (we consider the 1 sec sibly measure its redshift and luminosity. On the other hand, jet photon flux sensitivity of XGIS of 0.2 ph cm−2 s−1 , see Fig. not finding an EM counterpart will constrain merger types 36). Table 1 shows the expected rate of THESESUS/XGIS (such as BH-BH mergers), magnetic field strengths, and as- short GRB detections with a GW counterpart from merging trophysical conditions at the time of the merger. NS-NS systems (i.e. within the GW detector horizon). The quoted numbers are obtained by correcting the realistic es- 2.2.1 Gravitational wave transient sources timate of NS-NS merger rate from the jet collimation factor by assuming a jet half-opening angle range of [10-40] deg, NS-NS / NS-BH mergers: Collimated EM emission from Short and by taking into account the possibility to observe off-axis GRBs short GRBs up to 5Θ jet (see above). Compact binary coalescences (CBCs) are among the most By the time of the launch of THESEUS, gravitational ra- promising sources of GWs that will be detected in the next diation from such systems will be likely detectable by third- decade. Indeed, these systems are expected to radiate GWs generation detectors such as the Einstein Telescope (ET) up within the most sensitive frequency range of ground based to redshifts z∼2 or larger (see, e.g., Sathyaprakash et al. GW detectors (1-2000 Hz), with large GW energy output, 2012; Punturo et al. 2010), implying that almost all short −2 2 of the order of 10 M c , and gravitational waveforms well GRBs that THESEUS will detect, i.e., ∼20 short GRBs per predicted by General Relativity (see, e.g., Baiotti and Rez- year, will have a detectable GW emission. Indeed, it is likely zolla 2017, for a review). The expected rate of NS-NS sys- that at the typical distances at which ET detects GW events, tems inferred from binary pulsar observations and popula- the only EM counterparts that could feasibly be detected are tion synthesis modeling, is taken to lie between 10 and 1000 SGRBs and their afterglows, making the role of THESEUS Gpc−3 yr−1. To date, no NS-BH systems have been observed, crucial for multi-messenger astronomy by that time. Almost but the rate can still be predicted through population synthe- all short GRBs are accompanied by an X-ray afterglow that sis, constrained by the observations of NS-NS, to be ∼1- SXI will detect and monitor just after the burst emission. 1000 Gpc−3 yr−1 (see, e.g., Abadie et al. 2010a, and refer- Once localized with SXI, about 40% of detected short GRBs ences therein). Mounting indirect evidence associates short are expected to have a detectable optical/IR counterpart. The GRB progenitors to CBC systems with at least one neu- IRT could point at the SXI-localised afterglow within a few tron star (see, e.g., Berger 2014) and provides possible hints minutes from the trigger. If bright enough, spectroscopic that the merger of magnetized NS binaries might lead to observations could be performed on-board, thus providing the formation of a jet with an opening angle up to of ∼30- redshift estimates and information on chemical composi- 40 deg (so far the observed values range from 5-20 deg.; tion of circumburst medium. In addition, precise sky co- Rezzolla et al. 2011; Troja et al. 2016). GW observations ordinates will be disseminated to ground based telescopes combined with multi-wavelength follow-up campaigns in to perform spectroscopic observations. Distance measure- 12 Amati et al.

NS-NS / NS-BH mergers: Optical/NIR and soft X-ray isotropic emissions Nearly isotropic EM emission is expected from NS-NS / NS-BH mergers at minutes-days time scale from the merger. GW emission depends only weakly on the inclination angle of the inspiral orbit, and GW detectors will mostly trigger on off-axis mergers (i.e. for binary system with a non zero inclination angle). Both serendipitous discoveries within the large THESEUS/SXI FoV and re-pointing of THESEUS in response to a GW trigger will allow to study off-axis X- ray emission. One expected EM component is the late afterglow from the laterally spreading jet as soon as it decelerates (“orphan afterglows”; van Eerten et al. 2010). Peak bright- ness is expected at 1-10 days after the trigger, with peak X-ray fluxes equal or below ∼10−12-10−13 erg cm−2 s−1 at ∼200 Mpc (Kanner et al. 2012). Therefore, despite their low collimation, off-axis afterglows will be detected only for the most nearby CBC systems. Another nearly-isotropic emit- Fig. 11 Top panel: possible geometry of the conical jet, in spherical ting component is expected if a massive millisecond mag- coordinates with the origin at O. The observer is located at (D, Θobs, 0). The jet is moving with Lorentz factor Γ(Θ). Bottom panel: Luminosity netar is formed from two coalescing NSs. In this case, X- fraction (normalized to peak emission) as a function of observer angle, ray signals can be powered by the magnetar spindown emis- Lobs(Θobs), from Kathirgamaraju et al. (2017). The jet luminosity at sion reprocessed by the matter surrounding the merger site ∼40 deg is a factor of 300 fainter than that of the jet core. Nevertheless, such a misaligned jet can be detected by a γ-ray instrument if it takes (isotropically ejected during and after merger), with lumi- place within the Advanced LIGO detectability volume. nosities in the range 1043-1048 erg s−1 and time scales of minutes to days (Metzger and Piro 2014; Siegel and Ciolfi 2016a,b). Alternatively, X-ray emission may come from direct dissipation of magnetar winds (see, e.g., Zhang 2013; ments of a large sample of short GRBs combined with the Rezzolla and Kumar 2015). Numerical simulations suggest absolute source luminosity distance provided by the CBC- that such emission is collimated but with large half-opening GW signals can deliver precise measurements of the Hubble angles (30-40 deg, beaming factor of ∼0.2). As an additional constant (Schutz 1986), helping to break the degeneracies in channel in X-rays, the magnetar may accelerate the isotrop- determining other cosmological parameters via CMB, SNIa ically expelled matter through wind pressure to relativistic and BAO surveys (see, e.g., Dalal et al. 2006). Even with the speeds generating a shock with ISM (“confined winds”). second-generation GW detector network, the modest THE- Synchrotron radiation produced in the shock is emitted nearly SEUS EM + GW triggered coincidence number of 3-4 pre- isotropically, with an enhanced intensity near the equator. A dicted within the nominal mission life (not accounting for beaming factor of ∼0.8 is expected in this case (see, e.g., possible “off-axis” prompt GRB detection), can rises to 10 Gao et al. 2013). Overall, typical time scales for these X-ray or more when including SXI follow-up observations of GW signals are comparable to magnetar spin down time scales network error boxes. With 10 GW+EM events, the Hub- of ∼103-105 s, and the predicted luminosities span a wide ble constant could be constrained to 2-3%, thus providing range that goes from 1041 erg s−1 to 1048 erg s−1. With THE- a precise independent measure of this fundamental param- SEUS/SXI in combination with the second-generation de- eter (Dalal et al. 2006; Nissanke et al. 2010). In addition, tector network, almost all X-ray counterparts of GW events each individual joint GW+EM observation would provide from NS-NS merging systems will be easily detected simul- an enormous science return from THESEUS. For example, taneously with the GW trigger and/or with rapid follow-up the determination of the GW polarization ratio would con- of the GW-individuates sky region. These X-ray emission strain the binary orbit inclination and hence, when combined counterparts could be possibly detected up to large distances with an EM signal, the jet geometry and source energetics. with the third-generation of GW detectors (depending on the Likewise, a better understanding of the NS equation of state largely uncertain intrinsic luminosity of such X-ray compo- can follow from combined GW and EM signals (see, e.g., nent, see Table 1), providing a unique contribution to clas- Bauswein and Janka 2012; Takami et al. 2014; Lasky et al. sify X-ray emission from NS-NS systems and probes the 2014; Ciolfi and Siegel 2015b,a; Messenger et al. 2015; Rez- cosmic evolution. zolla and Takami 2016). In the optical band, the expected EM component is rep- ¿ resented by the so-called “macronova” (often named “kilo- THESEUS 13

Table 1 Number of NS-NS (BNS) mergers expected to be detected in the next years by second- (2020+) and third- (2030+) generation GW detectors and the expected number of electromagnetic counterparts as short GRBs (collimated) and X-ray isotropic emitting counterparts (see, e.g., Ciolﬁ and Siegel 2015b; Rezzolla and Kumar 2015) with THESEUS SXI and XGIS. BNS horizon indicates the GW detector sensitivity (see, e.g., Abadie et al. 2010a). The rate estimates of simultaneous GW+GRB detections assume that all BNS can produce a short GRB and take into account a combination of collimation angle range, XGIS FoV as a function of energy, and possible prompt oﬀ-axis detection. X-ray counterpart rate estimates assume that at least 1/3 of BNSs produce a long-lived NS remnant (but see Gao et al. 2016; Piro et al. 2017).

GW observations THESEUS XGIS/SXI joint GW+EM observations Epoch GW detector BNS horizon BNS rate XGIS/sGRB rate SXI/X-ray isotropic (yr−1) (yr−1) counterpart rate (yr−1) 2020+ Second-generation (advanced LIGO, ∼400 Mpc ∼40 ∼5-15 ∼1-3 (simultaneous) Advanced Virgo, India-LIGO, KAGRA) ∼6-18 (+follow-up) 2030+ Second + Third-generation ∼15-20 Gpc >10000 ∼15-25 &100 (e.g. ET, Cosmic Explorer)

Fig. 12 Expected X-ray fluxes at peak luminosity from different modelling of X-ray emission from NS-NS merger systems, that are among the most probable GW sources that will be detected in the following years by the second- and third- generation GW detectors. Grey solid lines show a typical GRB X-ray afterglow observed with Swift/XRT. Dots show the expected flux using fiducial parameters for each model. The black and dashed line show the THESEUS/SXI sensitivity as a function of the exposure time (credit: S. Vinciguerra; see also Fig. 26) nova”) emission (e.g., Li and Paczynski´ 1998). During NS- Macronovae are promising electromagnetic counterparts NS or NS-BH mergers, a certain amount of the typdally dis- of binary mergers because (i) the emission is nearly isotropic rupted neutron star mass is expected to become unbound and and therefore the number of observable mergers is not lim- ejected into space. This matter has the unique conditions of ited by beaming; (ii) the week-long emission period allows high neutron density and temperature to initiate r-process for sufficient time needed by follow-up observations. The nucleosynthesis of very heavy elements. Days after merger, detectability of macronovae is currently limited by the lack the radioactive decay of such elements heats up the ejected of sufficiently sensitive survey instruments in the optical/NIR material producing a thermal transient signal peaking in the band that can provide coverage over tens of square degrees, optical/near-infrared (NIR) band and with luminosities of the typical area within which GW events will be localized ∼1040 erg s−1 (see, e.g., Fernandez´ et al. 2016; Baiotti and by the Advanced LIGO-Virgo network. So far, observational Rezzolla 2017). Interaction of the ejected matter with sur- evidence of the macronova emission was obtained only in rounding ISM may also produce synchrotron radiation at few cases during the follow-up campaigns of the optical af- late times (∼weeks-months) peaking at radio wavelengths. terglows of short GRBs (Tanvir et al. 2013; Jin et al. 2015). Another fraction of the tydally disrupted neutron star mat- Figure 13 shows the expected macronova apparent magni- ter remains bound to the system forming an accreting disc. tudes for a source at 200 Mpc as well as the expected intrin- Disc winds outflows are expected to produce a more blue sic luminosity (Metzger and Berger 2012). Once the macronova optical emission peaking at earlier epochs (e.g. 1-2 days af- component is identified, source location can be accurately ter the merger), with luminosity of the order of a few times recovered, allowing for the identification of the host galaxy 1040−41 erg s−1, depending also on the nature of the central and the search for counterparts in other electromagnetic bands remnant (Kasen et al. 2015). (e.g. radio). 14 Amati et al.

thus obtain crucial insights on the innermost mass distribution, inaccessible via EM observations. The collapsar scenario invoked for long GRBs requires a rapidly rotating stellar core (see, e.g., Woosley 1993; Paczynski´ 1998), so that the disk is centrifugally supported and able to supply the jet. This rapid rotation may lead to non-axisymmetric instabilities, such as the fragmentation of the collapsing core or the development of clumps in the accretion disk (Gia- comazzo et al. 2011). GW/EM synergy plays a crucial role in the investigation of the nature of GRB progenitors and physical mechanisms. Indeed, gamma-ray emission and the multiwavelengths afterglow are thought to be produced at large distances from the central engine (i.e. >1013 cm). By contrast, GWs will be produced in the immediate vicinity Fig. 13 The dark grey region shows the expected macronova r-band apparent magnitude for a source at 200 Mpc as a function of time of the central engine, offering a direct probe of its physics. from the burst onset. Solid curves show the expected GRB afterglow Inspiral-like GW signals are predicted with an amplitude emission assuming different energetics and ISM densities. Red squares that might be observable by ET to luminosity distances of and blue triangles represent the afterglow detection (squares) and up- order 1 Gpc (see, e.g., Davies et al. 2002). With a rate of per limits (triangles) for a sample of short GRBs (Metzger and Berger −3 −1 2012). observed long GRB of ∼0.5 Gpc yr , THESEUS could provide a simultaneous EM monitoring of ∼1 long GRBs every two years. Off-axis X-ray afterglow detections (“or- During the next decade (2020-2030) we expect strong phan afterglows”) can potentially increase the simultaneous synergies between the second-generation GW detector net- GW+EM detection rate by a factor that strongly depends on work and several telescopes operating at different wavelegths the jet opening angle and the observer viewing angle. THE- such as: 1) the space-based telescopes James Webb Space SEUS may also observe the appearance of a NIR orphan Telescope (JWST), ATHENA and WFIRST; 2) the ground- afterglow few days after the reception of a GW signal due based telescope with large FOV like zPTF and LSST, which to a collapsing massive star. In addition, the possible large will be able to select the GW candidates in order to follow- number of low luminosity GRBs (LLGRBs) in the nearby up them afterwards; 3) the large telescopes, such as the 30-m Universe, expected to be up to 1000 times more numerous class telescopes GMT, TMT and ELT, which will all follow- than long GRBs, will provide clear signatures in the GW up the optical/NIR counterparts like macronovae; 4) the Square detectors because of their much smaller distances with re- Kilometer Array (SKA) in the radio, which is well suited to spect to long GRBs. GW+EM synergy plays a crucial role detect the late-time (∼weeks) signals produced by the in- in the investigation of the nature of GRB progenitors and teraction of the ejected matter with the interstellar medium. pysical mechanisms. Indeed, gamma-ray emission and the THESEUS/IRT will be perfectly integrated in this search, multiwavelengths afterglow are thought to be produced at due to its photometric and spectroscopic capabilities and its large distances from the central engine (i.e., > 1013 cm). By spectral range coverage. Light curves and spectra will be ac- contrast, gravitational waves will be produced in the inner quired, thus giving the opportunity to disentangle among ex- regions of the central engine, offering a direct probe of its pected different components associated to macronova events physics. (e.g. disk wind + dynamical ejecta contributions; Kasen et al. 2015). Soft Gamma Repeaters Fractures of the solid-crust on the surface of highly mag- Core collapse of massive stars: Long GRBs, Low Luminos- netized neutrons stars and dramatic magnetic-field readjust- ity GRBs and Supernovae ments represent the most widely accepted explanation to in- The collapse of massive stars are expected to emit GWs terpret X-ray sources such as giant flares and soft gamma since a certain degree of asymmetry in the explosion is in- repeaters (SGRs; see, e.g., Thompson and Duncan 1995). evitably present. Estimates of the GW amplitudes are still NS crust fractures have also been suggested to excite non poorely constrained and the expected output in energy has radial oscillation modes that may produce detectable GWs −8 −2 2 enormous uncertainties, ranging from 10 to 10 Moc . If (see, e.g., Corsi and Owen 2011; Ciolfi et al. 2011). The the efficiency of the GW emission is effectively very low, most recent estimates for the energy reservoir available in then only the third-generation GW detectors such as ET, a giant flare are between 1045 erg (about the same as the which will be operative at the same time as THESEUS, will total EM emission) and 1047 erg. The efficiency of conver- be able to reveal the GW emission from these sources and sion of this energy to GWs has been estimated in a number THESEUS 15 of recent numerical simulations and has been found to be vide a wealth of science opportunities. Here we emphasise likely too small to be within the sensitivity range of present two primary objectives: GW detectors (Ciolfi and Rezzolla 2012; Lasky et al. 2012). – reveal the violent Universe as it occurs in real-time, through However, at the typical frequencies of f-mode oscillations an all-sky X-ray survey of extraordinary grasp and sen- in NSs frequencies, ET will be sensitive to GW emissions sitivity carried out at high cadence. 42 44 as low as 10 -10 erg at 0.8 kpc, or about 0.01% to 1% of – discover new high-energy transient sources over the whole the energy content in the EM emission in a giant flare. In the sky, including supernova shock break-outs, black hole region of 20-100 Hz, ET will be able to probe emissions as tidal disruption events, magnetar flares, and monitor known 39 −7 low as 10 erg, i.e. as little as 10 of the total energy bud- X-ray sources, including GRBs, with low latency obser- get (see, e.g., Chassande-Mottin et al. 2010, and reference vations. therein). These objectives relate directly to the Cosmic Vision 2015- Neutrino sources 2025 questions under (3.2), providing the crucial electro- Several high-energy sources that THESEUS will monitor magnetic counterparts to GW sources such as compact star are also thought to be strong neutrino emitters, in particu- binary in-spirals and perhaps core-collapse SN, under (3.3), lar SNe and GRBs. The shocks formed in the GRB ultra- allowing the study of matter under extreme conditions around relativistic jets are expected to accelerate protons to ultrarel- black holes and in neutron stars, and under (4.3), examining ativistic energies and that, after interacting with high energy the evolving violent Universe through the study of quiescent photons, produce charged pions decaying as high energy and active massive black holes at the centers of galaxies. neutrinos (>105 GeV; see, e.g., Waxman and Bahcall 1997). By finding huge numbers of GRBs the survey will also per- Pulses of low energy neutrinos (<10 MeV) are expected to mit unprecedented insights in the physics and progenitors of be released during core-collapse supernovae (CCSNe) with GRBs and their connection with peculiar core-collapse SNe, an energy release up to 1053 erg. Indeed, low energy neutri- and substantially increase the detection rate and characteri- nos have been detected from SN1987A at 50 kpc distance. zation of sub-energetic GRBs and X-Ray Flashes. The pro- Still significant uncertainties are affecting supernova mod- vision of a high cadence soft X-ray survey in the 2020s to- els. GW and neutrino emission provide important informa- gether with a 0.7 m IRT in orbit will enable a strong synergy tion from the innermost regions as the degree of asymmetry with transient phenomena observed with the Large Synoptic in the matter distribution, as well the rotation rate and the Survey Telescope (LSST). strength of the magnetic fields, that can be used as priors Supernovae in numerical simulations (see, e.g., Chassande-Mottin et al. Supernovae mark the death of massive stars and are the prime 2010, and reference therein). Because of the neutrino very process by which heavy elements are distributed through the small cross-sections and low fluxes, neutrino detectors nec- Universe driving evolution in the stellar population. THE- essarily require huge amounts of water or liquid scintillator. SEUS will significantly advance our understanding of the Future Megatons detectors that are expected to work dur- SN explosion mechanism, detecting SNe at the very mo- ing the 3rd generation GW detectors, will reach distances up ment of emergence, gathering comprehensive, prompt data to 8 Mpc, that would guarantee simultaneous GW/neutrino and alerting follow-up communities to new events. The birth and EM detection of ∼1 SN per year. Very promising for of a new SN is revealed by a burst of high-energy emission such multi-messenger studies are the LLGRBs, given their as the shock breaks out of the star (giving access to measure- expected larger rate than for standard long GRBs (up to 1000 ments of the progenitor star radius). This has been spectacu- times more numerous) and their proximity. For long GRBs, larly captured just once, in a serendipitous Swift XRT obser- joint THESEUS and GW/neutrino observations would fur- vation of SN2008D (Soderberg et al. 2008): SNe are usually ther constrain progenitor models, clarifying the fraction of found only days to weeks after the explosion, as radioac- energy channeled via dynamical instabilities (Fryer et al. tive heating powers optical brightening. Theoretical calcu- 2002) and the relative neutrino/EM energy budgets. Neu- lations of shock breakout show that bright X-ray bursts of trino observations would also constrain the composition of L = 1043 − 1046 erg s−1 are expected for both Wolf-Rayet the GRB jet and the relation of GRBs to high-energy cosmic X stars and red supergiants (RSG) lasting 10-1000 s (Nakar rays (Abbasi et al. 2012). and Sari 2010). These progenitors are likely responsible for Type Ibc and most Type II SN respectively, which occur at 2.3 Exploring the Time-domain Universe rates of 2.6×10−5 and 4.5×10−5 Mpc−3 yr−1 (Li et al. 2011). SXI can detect these landmark events out to galaxies be- The SXI and XGIS will detect a large number of both tran- yond 50 Mpc. These bursts first emit hard spectra when the sient (Fig. 15) and steady X-ray sources serendipitously dur- shock is relativistic (Nakar and Sari 2012), also allowing de- ing regular observations (see Table 2). These data will protection by the XGIS. Shock breakouts from blue supergiants 16 Amati et al.

Fig. 14 Possible 1-year THESEUS/SXI sky exposure map (Galactic coordinates) based on the observing constraints and strategy described in next sections.

Fig. 15 Left: Time scales and luminosities of presently known soft X-ray transients (Jonker et al. 2013). Right: typical light curve of an X-Ray Flash, i.e. a GRB showing emission only in the X-ray energy range (BeppoSAX XRF020427; Amati et al. 2004).

Table 2 THESEUS detection rates for different astrophysical tran- sion physics with implications for using SN Ia as standard sients and variables. candles and to constrain dark energy (Sullivan et al. 2011). Transient type SXI rate Galactic Ia shock breakouts should be detectable by XGIS as very short high energy pulses (Nakar and Sari 2010), while Magnetars 40 day−1 SN Ia shock breakout 4 yr−1 those in binary with a red giant star may produce bright X- TDE 50 yr−1 ray bursts lasting minutes to hours via interaction with the AGN+Blazars 350 yr−1 companion wind (Kasen 2010). Thermonuclear bursts 35 day−1 Novae 250 yr−1 Relativistic SN shock breakout can also contribute a sig- − Dwarf novae 30 day 1 nificant fraction of the early X-ray flux seen in low-luminosity SFXTs 1000 yr−1 GRBs (see the cases of GRB 060218, and GRB 100316D; Stellar flares and super flares 400 yr−1 Campana et al. 2006; Starling et al. 2011), and THESEUS can make a significant contribution to this study, bridging the temporal gap between high and low energy X-rays of are expected to release comparable energy to RSGs, emit- current instrumentation. Fundamental parameters and pro- ting within the XGIS band. cesses, such as the radius of breakout and the driver of the With THESEUS, we aim at finding the first X-ray bursts light curve time scale, as well as the nature of the progenitor from thermonuclear Type Ia SN shock breakouts. The detec- stars themselves, remain unknown. THESEUS will discover tion of even a single Ia X-ray event is a powerful discrimi- all types of SN shock breakouts opening up this critical and nator between progenitor models, and constrains the explo- unexplored time domain in SN evolution. THESEUS 17

Tidal Disruption Events cretion activity is crucial. The accretion activity of the cen- Tidal disruption events (TDEs) offer a unique probe of the tral BH in active galaxies varies over a large range in am- ubiquity of super-massive black holes (SMBHs) in galaxies, plitude and timescale, due to variations in the emission effi- accretion on timescales open to direct study, and the nature ciency or accretion rate/efficiency in AGN (see, e.g., Mushotzky and dynamics of galactic nuclei. A star is tidally disrupted et al. 1993), or to changes in relativistic jet properties in when the tidal forces from the SMBH exceed the self-gravity Blazars (see, e.g., Marscher et al. 2010). SXI provides the of the star (Rees 1988). At this point half of the star is un- capability to monitor the X-ray flux of hundreds of AGN bound, while the other half falls back to form an accretion with ∼10% accuracy on daily timescales, and hundreds more disc at a characteristic rate of t−5/3. Such events are expected on longer timescales (Ueda et al. 2005). The survey strat- to be visible in UV and soft X-rays (see, e.g., Komossa et al. egy will permit an unbiased look at the long-term variability 2004; Gezari et al. 2012). The discovery by Swift of two of an unprecedentedly large AGN/Blazar sample at depths highly luminous outbursts from galactic nuclei implies that never reached before. SXI monitoring will enable regular at times a fraction of this energy is deposited in a new rel- multi-wavelength campaigns to occur in order to probe the ativistic jet outflow (Levan et al. 2011; Bloom et al. 2011; emission mechanisms and the geometry of the central active Burrows et al. 2011), offering a new route to their identifica- regions. tion and an opportunity to study newly-born jets. THESEUS The observation of correlated X-ray/radio AGN variabil- is ideal for both the discovery and characterization of TDEs, ity with THESEUS and SKA, can be strongly diagnostic, al- opening new windows on numerous astrophysical questions. lowing searches for mass-related lags and radio-frequency- TDEs offer a unique probe of SMBH presence across the related lags, opening up the jet physics. It is generally agreed Universe by revealing formerly dormant SMBH in galaxies that the radio to UV/X-ray emission from blazars is syn- 8 across the mass scale up to ∼10 M . The key to extracting chrotron emission from a relativistic jet oriented towards the most from these events is to obtain identifications early, the observer, with the higher energy emission arising from while the first material is falling back. This in turn allows Compton scattering of seed photons by particles in the jet, multi-wavelength observations at the peak of the light from although many details of the jet structure are still unclear. which one can infer the mass of the black hole and the nature The expected sensitivity of future radio observations is such of the in-falling star. This can be compared to the properties that radio-X-ray studies of radio quiet Seyfert galaxies will of the galaxy and the MBH-σ relation. TDEs provide unique then be possible. In particular, THESEUS will allow the de- laboratories for studies of physics under extreme conditions. tection of X-ray flaring activity in Seyferts. Connecting flare They allow us to study accretion in active galaxies from on- states and X-ray/radio variability in radio quiet AGN, would set to a return to dormancy, on timescales of only a few have implications for AGN evolution/feedback models. years. Through this time we can study the behaviour of ac- THESEUS will monitor the bright AGN population and cretion at a variety of rates, and the processes of disc and jet trigger follow-up observations by both THESEUS itself and formation. Jets in the relativistic TDEs are promising loca- other multi-wavelength facilities to measure the relation be- tions for the acceleration of ultra-high-energy cosmic-rays. tween different energy bands and the lag between bands which Finally, the rate and nature of the TDEs provides insight into constrain the emission process. For example, Synchrotron the central dynamics of galaxies. An exciting possibility is Self-Compton emission predicts a TeV lag roughly equal using TDEs as tracers of BH-mergers. The dynamical im- to the light travel time across the emission region, whereas pact of the merger on surrounding stars increases the TDE for external seed photons, assuming the source of variabil- rate by several orders of magnitude to > 0.1 yr−1, raising the ity is in the relativistic electrons of the jet, simultaneity is possibility of observing multiple events from a single galaxy expected. Measurement of the complete shape of the syn- undergoing a BH merger. For the classical TDEs, the SXI ef- chrotron spectral component from radio to hard X-ray con- fective horizon in a single orbit is ∼200 Mpc (z ∼0.05). The strains the particle acceleration process in the jet and the rate of relativistic TDEs is uncertain, but both SXI and XGIS balance of acceleration and radiative cooling; if energy is can see them to z ∼1 (L = 1048 erg s−1). For moderately peak input via hadrons rather than via electrons, radiative losses conservative assumptions (beaming to 5% of the sky in 10% will be less, so the spectrum will be harder at higher energies of TDEs) it is quite possible that the relativistic TDE rate (see, e.g., Tramacere et al. 2007). In the THESEUS era, ten will exceed the classical one. times greater TeV sensitivity than now will be provided by the Cherenkov Telescope Array, allowing the routine study AGN and Blazars of hundreds of blazars. VHE gamma ray emission is char- Active galaxies are the most powerful continuous sources acterized by large outbursts during which detailed measure- of energy in the Universe and are powered by supermassive ments can be made. Deep monitoring observations can also BHs in galactic centres. They also help control the growth of be made with XGIS whose hard X-ray spectral response is the stellar population in galaxies, so understanding their ac- ideal for defining the synchrotron shape. 18 Amati et al.

Accreting Binaries launch jets. The recent radio discovery of two high accretion Thermonuclear X-ray bursts are produced by runaway nu- rate systems, including dwarf novae (Kording¨ et al. 2008, clear burning on NS surfaces in our galaxy, often reach- 2011), makes crucial the sinergy with SKA to understand ing the Eddington luminosity limit (Strohmayer and Watts jet-launching processes irrespective of the compact object 2006). THESEUS probes a regime of deep nuclear carbon nature (WD, NS or BH). Truly magnetic systems are the burning, and its thermal effects on neutron star crusts and X-ray brighest among CVs. However the state changes are cores, rarely observed before now (Brown 2004; Cumming not abrupt but on a long-term scale (months-yrs). THESEUS and Macbeth 2004). These infrequent hours-long “super- will provide excellent coverage of the outbursts of classical bursts” are efficiently detected in the THESEUS sky sur- neutron star and black hole X-ray binaries, for example Su- vey due to its high exposure. It also captures seconds-long pergiant Fast X-ray Transient variability reaches up to a fac- hydrogen- and helium-burning thermonuclear bursts more tor of 106 (Romano et al. 2015), with peak luminosities up frequently. A large sample of burst properties will test mod- to 1038 erg s−1; the hour-timescale flares from these OB plus els that predict nuclear burning dependence on mass accre- (presumed) NS systems have frequently triggered the Swift- tion rate (Heger et al. 2007), and add to previous burst sam- BAT. THESEUS can constrain the temperature and optical ples collected by BeppoSAX and RXTE (Keek et al. 2010). depth of the accretion column (Farinelli et al. 2012; Bozzo Classical and Recurrent Novae are produced by runaway et al. 2016), and the origin of the bright flares possibly due thermonuclear burning on the surfaces of a white dwarf in a to wind accretion onto a magnetar (Bozzo et al. 2008). THE- close binary system. SXI will, for the first time, detect the SEUS will detect and provide localization for several black- initial thermonuclear runaway burning phase, which lasts hole transients, monitoring daily their X-ray spectral evo- only a few hundred seconds. Previous X-ray studies have lution throughout their full outburst. Pointed observations only been able to probe the shock-heated wind ahead of with IRT will provide strictly simultaneous IR photometry the ejecta and the steady burning phase that emerges later (and often spectroscopy) with very good statistics, allowing (see, e.g., Osborne et al. 2011; Schwarz et al. 2011; Os- an unprecedented study of the disk-jet connection across all borne 2015). X-ray spectra and temporal profiles provide accretion regimes. constraints on nuclear reaction processes, the white dwarf mass, and the underlying convective mixing (see, e.g., Star- Magnetars rfield et al. 2009). THESEUS will be able to monitor the Magnetars, young NS with external magnetic fields of 1013- brightnesses of the Super-Soft Sources (Greiner 1996), can- 1015 G, are among the most powerful and spectacular high- didate progenitors for Type Ia SNe, to give a significantly energy transients in the sky. They are characterized by the improved view of their accretion behaviour. Both Classical emission of highly super-Eddington short bursts of emission and Recurrent Novae are also sources of hard X-ray emis- (Soft Gamma-ray Repeaters) and more rare Giant Flares (lu- sion (Sokoloski et al. 2006; Mukai et al. 2008) variable with minosity up to 1047 erg s−1). Magnetars differ from other time which appears later than the SSS phase. The onset of more common classes of neutron stars because all their emis- this emission component probes the existence of shocked sion (both persistent and bursting) is powered by the gradual material within the ejected shell. In addition the recent and and/or impulsive dissipation of magnetic energy, rather than new discoveries of Novae (both classical and recurrent) as by rotational energy or accretion (Thompson and Duncan source of particle acceleration by Fermi-LAT, and thus a 1995). There is evidence that the field in the interior of mag- class of gamma-ray emitters, challenges our knowledge of netars can exceed 1016 G, probably as a result of their rapid these transient objects (Cheung et al. 2016). The wide en- rotation at birth (1-2 ms). About twenty sources believed to ergy coverage of the SXI and XGIS instruments will al- be magnetars are currently known in our Galaxy and in the low us to track the temporal evolution of the different emis- Magellanic Clouds, but since most of them are transients sion components along the outburst. All this will provide a with long quiescent periods, the total population waiting to significant improvement of our still poor knowledge of the be discovered is certainly much larger (Mereghetti 2008). tight link between accretion processes and explosion mech- Magnetars can produce Giant Flares thought to be due to anisms. star crustal fractures. Their EM emission consists of an ini- Accretion-driven outbursts and state changes are also tial, short (<0.5 s) spike of hard X-rays followed by a tail of seen in white dwarf, NS and BH binaries. Dwarf Novae softer X-rays lasting minutes and modulated by the NS ro- outbursts occurring in white dwarf accreting systems (cat- tation (P∼2-12 s). These extremely bright initial spikes can aclysmic Variables) will be routinely observed in both soft be detected with the XGIS to considerable distance. Based X-rays and optical/nIR ranges. This unique opportunity will on the rate of the few Giant Flares observed to date, and the allow to solve the still open question on dwarf nova diversity XGIS’s energy range will be better suited for the detection in optical and X-ray behaviours (Fertig et al. 2011). Further- of such events than current coded-mask detectors due to its more, cataclysmic variables were thought to be unable to lower energy threshold. THESEUS 19

The persistent X-ray emission from known magnetars is Some SN Ibc must therefore harbour an additional key in- too faint and strongly absorbed to be detectable by SXI when gredient, i.e. a central engine - likely a nascent black hole these sources are in a quiescent state; however, the increased - that drives the explosion and launches a relativistic out- level of X-ray emission associated with flares and periods flow producing the GRB. Why this happens is not clear. The of increased bursting activity will be easily detectable. Thus missing link between the two classes of explosions may be THESEUS triggers will enable detailed observations of these found amongst the X-Ray Flashes (XRFs, see Fig. 16), com- events. These “intermediate flares” are more frequent than monly considered as a softer sub-class of GRBs (but see the Giant Flares. The wide field of view of SXI and the fre- also Ciolfi (2016)), and LL-GRBs, likely related to a pop- quent sky coverage will, for the first time, allow detection of ulation of only slightly relativistic SN which have recently a large number of flares and obtain a reliable estimate of the been found in the radio. Current X-ray facilities are quite in- frequency of such events. The count rate expected in SXI for sensitive to such events, which are typically characterized by a typical intermediate flare will allow detailed time-resolved soft spectra (low Epeak). These events will make up ∼1/3 of study of flare properties. the THESEUS GRBs, populating the existing gap between GRBs and ordinary SN (Fig. 15). Because of their low lumi- Stellar Coronae nosity, we expect that most of these events will be at z <0.5 Stellar Flares of all sizes are important probes of coronal and that, in terms of rate density, they constitute the bulk of structures and their energetics, and thus, the underlying stel- GRB population. Present surveys are in fact biased towards lar magnetic dynamo (see, e.g., Reale 2007; Aschwanden harder, more luminous events (less than 5% of long Swift and Tsiklauri 2009). THESEUS will quantify the extreme bursts are at z <0.5; Jakobsson et al. 2012). The detection of “super-flares” of nearby magnetically active stars >104 times intrinsically faint, X-ray soft GRBs can only be done at low more energetic than the Sun’s largest flares. X-ray flares X-ray energies, when there are enough photons for their de- have long been detected and cataloged (see, e.g., Pye and tection. An important goal of THESEUS is to understand the McHardy 1983; Favata 2002; Gudel¨ 2004), but rare “super- paths of stellar evolution leading to the production of GRBs flares” can briefly (∼1000 s) exceed the star’s quiescent bolo- and of SNe, as described in below. metric luminosity, and only a handful are known (see, e.g., RS CVn binary II Peg and dMe star EV Lac; Osten et al. GRB physics and circum-burst environment 2007, 2010). As an X-ray mission, THESEUS will directly Current GRB facilities do not permit prompt X-ray obser- address the high-energy ionising radiations of primary im- vations in the spectral band where most of the photons are portance for solar-terrestrial interactions. THESEUS will pro- emitted. Around 60% of THESEUS GRBs will be simulta- vide estimates of coronal loop structure sizes and energy re- neously detected by SXI and XGIS during the prompt emis- lease in flares. Occurrence rates and luminosities constrain sion, allowing for the first time measures of the energy spec- stellar models, and also affect the conditions for life in the trum from 0.3 keV to 10 MeV, in a domain little explored, habitable zone. Although much progress has been and con- but crucial to discriminate among different emission models tinues to be made from studies of our own Sun, many ques- and determine the effects of intrinsic absorption in the GRB tions remain regarding fundamental flare processes (see, e.g., environment (Fig. 17). Such observations are needed to val- Gudel¨ 2004; Benz and Gudel¨ 2010); THESEUS will allow idate models based on synchrotron emission and to measure the theoretical models for energy release and propagation to the impact of the GRB on its surrounding. be tested within a greatly expanded phase space. SXI will It is worth noting that a number of recent studies have be the primary instrument for the stellar-flare survey, and found evidence of a sub-dominant thermal emission in the its photon-energy bandpass is well-tuned to stellar-coronal prompt emission spectrum (Ryde et al. 2010; Guiriec et al. emissions (which have typical characteristic temperatures 2011; Basak and Rao 2015). The thermal emission is also ∼0.1-10 keV). reported until very late emission phase of the longest ultra- long GRB 130925A and it has been shown to have a very similar spectral evolution as a ordinary long GRB 090618 2.4 GRB physics, progenitors and cosmology (Basak and Rao 2015). The former was observed with the fine resolution data of Swift/XRT, Nustar and Chandra, while X-ray Flashes, sub-energetic GRBs and GRB-SN connection for the later XRT data was available at the late prompt emis- It is well established that long GRBs are linked to SN origi- sion phase. As such studies rely on the focusing observa- nating from the core collapse of a stripped-envelope massive tions, they are rare and miss the evolution in the initial phase star (SN type Ibc). However, for GRBs the bulk of the ex- of emission. With THESEUS such studies will be routinely plosion energy goes into relativistic ejecta, while the vast done and a broadband, fine resolution spectrum will be ob- majority of SN Ibc show sub-relativistic ejecta with an en- tained from very early emission phase. Firstly, it will be an ergy release several orders of magnitude lower than GRBs. enormous step forward to study the evolution of the indi- 20 Amati et al.

Fig. 16 Left: distributions in the spectral peak energy (Ep) - Fluence plane of soft X-Ray Rich (XRR) GRBs and X-Ray Flashes (XRFs) compared to that of normal GRBs (Sakamoto et al. 2005). Right: Blast wave velocity and energy for massive star explosions (adapted from Soderberg et al. 2010). Soft/weak GRBs may constitute the bulk of the GRB population and the link with other explosive events associated to the death of massive stars. vidual spectral components from the early phase, secondly, a stellar mass black hole. Efficient extraction of broadband this will also increase the sample size and help in finding the spectra from gamma-ray light curves is made possible by spectral diversity or a unification across the GRB catalog. Graphics Processor Units (GPUs), allowing deep searches by using banks of millions of chirp templates developed to GRB physics in EM-GW extract chirp-based spectrograms from noisy time-series of GRBs and, more generally, core-collapse supernovae may GRBs (BeppoSAX, THESEUS) and LIGO-Virgo or KA- be multi-messenger sources of electromagnetic (EM) and GRA alike. gravitational waves (GW) by their potential association with neutron stars and black holes. These alternatives may leave their imprint in high-frequency modulations of associated high energy emission, in particular, by mis-alignment (align- Complete samples ment) of magnetic moments with the spin of a magnetar In order to study properties of GRBs, their X-ray and op- (black hole). tical/NIR afterglows, and their hosts is important to handle High resolution light curves of relatively bright GRBs a sample that is not biased towards classes (i.e. a complete are hereby expected to show non-smooth (smooth) broad- sample), because of limitation during the observations. Un- band Kolmogorov spectra. Smooth broadband Kolmogorov til now, several GRB complete samples have being created spectra have been found up to the comoving frequency of a (see, e.g., Perley et al. 2016; Greiner et al. 2001; Salvaterra few kHz of bright LGRBs sampled at 2 kHz from the Bep- et al. 2012). In addition to these, other tools to overcome the poSAX catalog (see Fig. 18). problems of unbiased distributions with robust and sophys- THESEUS exceeds BeppoSAX in collecting area and ticated statistical techniques have already been successfully time resolution, allowing a more detailed analysis of individ- applied to GRB prompt and afterglow emission (Dainotti ual events and/or events at higher redshifts. Smooth broad- et al. 2013a, 2015). The capability of THESEUS to detect band spectra from THESEUS would further evidence the most afterglows in the IR, excluding the few highly extin- black hole inner engines, absent any high frequency mod- guished or at extreme redshift (<10%), will allow us for the ulations in spectra of gamma-ray light curves. first time to build a complete sample of GRB afterglows ob- Results such as these provide potentially powerful pri- served in X-rays and IR. The fact that THESEUS will not be ors to our searches for GW emission accompanying LGRBs. limited by weather conditions and visibility constraints, but LGRBs from rotating black holes, for instance, will pro- only from pointing limitation and froregronud Galactic ex- duce their highest GW frequencies from non-axisymmetric tinction, is a strong advantage in respect to ground based fa- mass motion at the Inner Most Stable Circular Orbit (ISCO) cilities dedicated to GRB follow-up (e.g. RATIR, GROND, powered by the ample reservoir in angular momentum of REM). THESEUS 21

Fig. 17 By satisfying the requirements for the main science (Fig. 22), in particular the extension of its energy band down to 2 keV with large area and 300 eV energy resolution, the THESEUS/XGIS will show unique capabilities for discrmininating among different GRB emission models (left) and detecting absorption features expected at energies <10 keV (circum-burst environments and X-ray redshift determination). Left: Simulated XGIS low-energy (SDD) spectra of the first 50 s of GRB 090618 (Izzo et al. 2012) obtained by assuming either the Band function (black) or the power-law plus black-body model (red) which equally fit the Fermi/GBM measured spectrum, which is also shown (blue). The black-body plus power-law model components best-fitting the Fermi/GBM spectrum are also shown (black dashed lines). Right: Simulation of the transient absorption feature in the X-ray energy band detected by BeppoSAX/WFC in the first 8 s of GRB 990705 (Amati et al. 2000) as would be measured by the XGIS.

Fig. 18 Broadband spectrum obtained as an average of 42 relatively Fig. 19 The redshift distribution of THESEUS GRBs during a 5 yr bright bursts from the BeppoSAX catalog through butterfly filtering mission lifetime compared to the actual distribution of Swift GRBs (purple curve) using a bank of 8.64 million chirp templates. The broad- (blue) during the same period. GRBs with a photometric redshift are in band Kolmogorov spectrum extends standard Fourier-based spectra green, and those with a spectroscopic redshift are in red. (blue curve) up to a few kHz in the comoving frame. The absence of any high frequency bump favors inner engines harboring black holes rather than magnetars (from van Putten et al. 2014). nature of the central engine. Indeed, the observer may see simultaneously photons that have been emitted in different Multiwavelength prompt emission times and regions of the flow, and also with different phys- Right now, thanks to Swift/UVOT and ground based opti- ical origin, e.g., synchrotron or synchrotron self-compton cal/NIR telescopes dedicated to the rapid follow-up of GRB emission. However, there are only a few tens of bursts in afterglows, it is possible to simultaneously follow-up the 12 years of Swift activity that could be long and bright enough prompt emission from optical to X-ray to Gamma-rays. These to be detected in optical (Levan et al. 2014). Indeed, up to observations allow us not only to better constrain the spec- now only five events have been studied in such detail (see, tral energy distribution from optical to Gamma-rays and their e.g., Bloom et al. 2009; Rossi et al. 2011; Stratta et al. 2013; lightcurves, testing the standard model, but also to test the Troja et al. 2017), and while they probe that standard fireball 22 Amati et al. model can explain the observations, in some cases the opti- engine of GRBs. The study of the optical/NIR and X-ray cal and high-energy emission seems unrelated, or require a afterglows unveils the properties of the environment. It is more complex modeling of the jet structure. Moreover, these well known that the circumburst density profile influences observations have been performed in the optical, which is the shape of the GRB light curves and spectra (see, e.g., more affected by foreground and host line of sight dust ex- Racusin et al. 2009) distinguishing by ISM and wind en- tinction. With THESEUS/IRT capability of starting to obtain vironments (see, e.g., Schulze et al. 2011). Moreover, dust the first images within the first 5 min from the trigger, it will and gas in the line of sight dim the optical/NIR and X-ray be possible to detect optical prompt emission for the longest afterglows, respectively (see, e.g., Greiner et al. 2011). Their GRBs, roughly 10 to 20 GRBs per year. This will dramati- systematic study will unveil the properties of the environ- cally increase the number of events to study, and allowing us ment where GRBs explode. Unfortunately, up to today this to statistically explore the parameter space of several mod- has been limited by the different time coverage of X-ray els, shedding light on the structure of the jet during its first and optical/NIR observations and sensitivity to the late af- phases. terglows. THESEUS will likely solve this problem thanks to the simultaneous observations of optical/NIR and X-ray afterglows. X-ray early and late afterglow Opposed to what was initially believed, X-ray afterglows do not have a simple power-law decay. On the contrary, the vast Optical/IR afterglow detection with IRT majority shows a canonical behavior (Nousek et al. 2006): As shown by Kann et al. (2017), within the first hour all an initial rapid decay during the first few hundred seconds, known optical afteglows have R<22. A classical optical af- a slow fading plateau phase that can persist even longer than terglow has a spectral slope β∼1, which translates in a color 104 s, and a final power-law decay, with a possible achro- R-H∼1 mag (AB photometric system), thus within the first matic break. While it is clear that the initial rapid decay cor- hour all known afterglows have H<21. IRT will observe op- responds to the tail of the prompt emission, the plateau phase tical afterglows longer than 30 min within 1 hour from the is difficult to explain within the collapsar scenario, because trigger, reaching HAB∼20.6. The optical/NIR imager GROND, it requires a long activity of the central engine. Alternatively, reaching 1 mag fainter limits only, has been able to detect the necessary energy may come from the spin-down activity ∼90% of all GRBs detected by Swift within 4 hours from of a magnetar formed during the collapse (see, e.g., Zhang the trigger (Greiner et al. 2011). Note that the host extinction and Mesz´ aros´ 2001; Dall’Osso et al. 2011; Rowlinson et al. will mostly have a negligible effect, with only a few cases 2014; Rea et al. 2015). To complicate this view, X-ray flares (∼10%) with AV>0.5, which will noticibly dim (>1 mag) the (not visible in gamma-rays), probably due to late emission, observed NIR afterglow when the redshift is z>4, and still indicate that the central engine is still active. The relativis- obtaining a detection rate of ∼90%. However, at these red- tic outflow of a GRB is likely collimated in a jet (Sari and shift dusty environments are less common, because dust did Piran 1999). Since the jet slows down, at some point the not have the time to accumulate in the star forming regions. relativistic open-angle becomes larger than the relativistic Notably, the higher rate of THESEUS GRBs will allow us to jet-opening angle. Thus the observer starts to see a deficit of better understand the shape of dust extinction curve at high photons compared to the case of isotropic emission, leading redshift which is now unexplored, the presence of 2175A to an achromatic break in the light curve. These breaks, to- absorption in GRB SEDs in high redshift environments and gether with the knowledge of the redshift and the measure to test different models for dust grains. of the isotropic energy, allow us to estimate the jet-opening angle and the collimated energy (and used as cosmologi- Short GRBs cal indicator). Achromatic jet-breaks have been observed in Short GRBs are the least understood class of GRBs. Our un- optical/IR, however they often do not coincide with breaks derstanding of the nature and range of progenitors of short observed in X-rays, indicating that our knowledge of the af- GRBs remains hampered by their small number, and THE- terglows emission is still limited, and questioning if the jet- SEUS will contribute importantly to increasing the sample angle and collimated energy that have been estimated are for study. More fundamentally, the observations of THE- right. Even if from the theoretical side many explanations SEUS will be crucial for the interpretation of candidate sig- (energy injections, double jet, structured jets) have been pro- nals in advanced detectors of gravitational waves. As dis- posed to interpret the afterglow emission from IR/optical cussed above, THESEUS/XGIS will find ∼20 SGRBs yr−1, to X-rays, more multi-frequency observations are necessary most of which will be localized more precisely with SXI (see, e.g., Willingale and Mesz´ aros´ 2017). Compared to to- follow-up. At least 1/3 of the short GRBs are followed by a day, the larger number of THESEUS GRBs and the more period of soft X-ray emission lasting 10-100 s. This emis- sensitive spectra observed with XGIS will allow us to bet- sion carries an energy comparable and often larger than the ter understand the nature of the afterglow and of the central initial spike, and it will be easily detected by THESEUS. THESEUS 23

already be derived (see, e.g., Ghirlanda et al. 2004; Am- ati et al. 2008; Dainotti et al. 2013b). Current (e.g., Swift, Fermi/GBM, Konus-WIND) and forthcoming GRB experiments (e.g., CALET/ GBM, SVOM, Lomonosov/ UFFO, eXTP/ WFM) will allow us to constrain ΩM and the dark energy equation of state parameters w0 and wa, describing the evolution of w according to w = w0 + wa(1 + z), with an accuracy comparable to that currently obtained with Type Ia supernovae (Fig. 21). The order of magnitude improvement provided by THESEUS on the sample of GRBs, with measured redshifts and spectral parameters, will allow us to further reﬁne the reliability of this method. This will oﬀer the unique opportunity to constrain the geometry, and therefore the mass-energy content of the universe back to z∼5, thus even extending the investigations of EUCLID and of the next generation large scale structure surveys to the entire cosmic history.

Synergies with JWST and E-ELT Fig. 20 Observed R band lightcurves of long GRBs. Highligthed Recently, it has been shown that GRB 111209A is linked to is the ultra long GRB 111209A and the extremely extinguished GRB 130925A (bottom curve). Data is corrected for Galactic extinc- a SN with properties dissimilar to any known GRB-SN, with tion. Adapted from Kann et al. (2017). We also show in the figure with a spectrum more in accordance with Superluminous super- blue lines the THESEUS/IRT sensitivity (dashed line spectroscopy, novae (SLSN; see, e.g., Greiner et al. 2015), and like them solid line imaging). was probably not powered by the standard collapsar central engine. The high rate of detection of THESEUS GRBs will THESEUS will extend the search of this intriguing feature significantly increase the number of long GRBs linked to down to a factor of ∼10 below present upper limits, allowing SLSNe which can be studied with the planned JWST and E- also for the search of “orphan extended tails” of SGRBs if ELT, shedding light on the GRB progenitors and their driv- they are not beamed (Bucciantini et al. 2012). ing mechanisms. With the exception of the brightest hosts at low redshift (z<2), IRT will not allow to detect hosts in NIR. However, their contribution will be visible as emission Probing expansion history of the universe and dark energy and absorption lines in the afterglow spectra (Hjorth et al. with GRBs 2012; Savaglio et al. 2009), and therefore we will be able to In a few dozen seconds, GRBs emit up to 1054 erg in terms of measure their spectroscopic redshift. Moreover, the localiza- an equivalent isotropically radiated energy E , so they can iso tion of the NIR afterglow and its immediate distribution to be observed to z∼10 and beyond. By using the spectral peak the astronomical community, will permit others to follow- energy - radiated energy (or luminosity) correlation E - p,i up the event with other ground and space based facilities, E (Amati et al. 2002; Yonetoku et al. 2004), the luminos- iso in particular the future instruments on the JWST and 30 m ity at the end of the plateau emission and its rest frame du- ground based telescope (e.g., ELT, GMT, TMT). We thus ration correlation (Dainotti et al. 2008) and the fundamental summarize the most relevant synergies in the following two plane relation, an extension of the previous one by adding points: the peak luminosity in the prompt emission (Dainotti et al. 2016) are robust correlations studied and discussed for many – The Environment of GRBs with the future JWST and years. Through these correlations, it has been demonstrated 30 m class telescopes. THESEUS will enhance the rate that GRBs offer a very promising tool to probe the expansion of GRBs discovered at high redshift. At present the sam- rate history of the universe beyond the current limit of z = 2 ple of GRB host galaxies at z>6 is limited to 9 events. (Type-Ia SNe and Baryonic Acoustic Oscillations from QSO In the late 20’s the rate of GRBs at z>6 is expected to be absorbers). Additionally, the Ep,i - Eiso correlation has been >5 per year. Considering visibility constraints, we ex- shown to hold within the individual pulses of GRB prompt pect to have ∼2-3 targets yr−1. JWST and future 30 m emission which is a strong argument against any instrumen- class telescope will allow us to search even for dwarf tal selection bias, and conveniently increases the sample size host galaxies with HAB ∼ 31 mag by using few hours for such studies (Basak and Rao 2013). imaging with E-ELT. If the host will be brighter than With the present data set of GRBs, cosmological pa- H∼27, spectroscopy will be possible. A prompt alert will rameters consistent with the concordance cosmology can permit to use the optical afterglow as a reference star 24 Amati et al.

Fig. 21 Left: SNe-Ia + GRB Hubble diagram obtained by exploiting the correlation between spectral peak energy (Ep) and radiated energy or luminosity (Eiso, Liso) in GRBs (Demianski et al. 2017). Right: determination of the dark energy equation of state parameters w0 and wa with the expected sample of GRBs form THESEUS by using the same (Amati and Della Valle 2013a).

Fig. 22 Conversion from THESEUS science goals to instrument and spacecraft requirements.

for Adaptive Optics (AO) in 30 m class telescope and 2012), on the aversion of long GRBs for high metallici- perform IFU studies of the environment of the GRB, ties (see, e.g., Schulze et al. 2016), and in general on the with angular resolution six times better than with JWST. properties of the environment (e.g., star formation, gas This will provide information on the metallicity/dust/gas inﬂow, dust content) needed for the formation of GRB gradients close the GRB explosion sites, shedding light progenitors. One of the driving mechanisms for the for- on the most dusty environments (see, e.g., Rossi et al. mation of the massive stars at high redshift, including THESEUS 25

progenitors of long GRBs, may be the inflow of pristine over a continuous redshift range where the bulge-blackhole gas during galaxy interactions (see also Michałowski et al. mass relation is being built up and established, and the main 2015). The high angular resolution and sensitivity achiev- sequence of star formation is well-studied. With excellent able with imaging and spectroscopy instruments mounted image quality, THESEUS R∼500 grism can also provide on JWST and 30 m class telescopes will permit us to spatially-resolved spectral information to highlight AGN emis- study the morphological properties and the UV emission sion, and identify galaxy asymmetries. of the host of high-z GRBs. These observations will al- The imaging sensitivity of THESEUS is about 6 magni- low us to test the hypothesis that galaxy interactions at tudes lower than for JWST in the same exposure time; nev- high redshift induce the formation of very massive stars ertheless, its availability ensures that many important statis- and GRB progenitors. tical samples of active and evolved galaxies, selected from – The missing host galaxies of short GRBs. The short GRB a wide range of sources can be compiled and diagnosed in offsets normalized by host-galaxy size are larger than detail at these interesting redshifts. Samples can be drawn those of long GRBs, core-collapse SNe, and Type Ia from the very large WISE- and Herschel-selected infrared SNe, with only 20% located at within the galaxy radius. samples of galaxies, from EUCLID 24-mag large-area near- These results are indicative of natal kicks or an origin in infrared galaxy survey, augmented by near-infrared selec- globular clusters, both of which point to compact object tion in surveys from UKIDSS (whose deepest field reaches binary mergers (Berger 2014). About 20% of well local- approximately 1 mag deeper than EUCLID wide-area sur- ized SGRBs (∼7% of the total number of SGRBs) have vey in the H band) and VISTA, and in the optical from LSST been classified as host-less (Fong et al. 2013). The non- and SDSS. Spectra for rare and unusual galaxies and AGNs optimal X-ray localizations do not permit us to solve this selected from wide-field imaging surveys can be obtained problem, because several galaxies lie within the X-ray using the wide-field of THESEUS grism, thus building an error circle, as it is shown in deep optical-NIR HST im- extensive reference sample for studying the environments ages. THESEUS/IRT will allow us to localize sGRB af- of the selected galaxies and AGNs, identifying large-scale terglows within a region (<1 arcsec error circle) small structures and allowing overdensities to be measured. The enough to search for the host galaxies using the future parallel acquisition of spectral and imaging data over sub- JWST and 30 m class telescopes and investigate if these stantial areas would build up a clear picture of the environ- might be inside very faint galaxies or may have been ments, including serendipitiously-selected spectra, all tak- ejected by natal kicks or dynamics. Distinguishing being advantage of the spectral resolution delivered for THE- tween these two scenarios gives constraints on the for- SEUS’s primary science of investigating GRB afterglows. mation of NS binaries.

3 Scientific Requirements 2.5 Observatory science with IRT THESEUS is designed to achieve two primary scientific goals: Fielding an IR-specified spectrograph in space, THESEUS 1. Explore the physical conditions of the early Universe by would provide a unique resource for understanding the evo- providing a complete census of GRBs in the first billion lution of large samples of obscured galaxies and AGN. With years. a rapid slewing capability, and substantial mission duration, 2. Perform an unprecedentedly deep monitoring of the X- the mission will provide a very flexible opportunity for sev- ray transient Universe thus playing a fundamental role eral fields of astrophysics, in a way similar to what is cur- in the coming era of multi-messenger and time-domain rently done by Swift/XRT in the X-rays. For instance, it astrophysics will be possible to take efficient images and spectra of large samples of galaxies with minute-to-many-hour-long cumu- These goals are very demanding in terms of technology and lative integrations. A continuous spectral coverage with no require a combination of on-board capability to perform wide- blockages due to atmospheric opacity ensures that identical field X-ray imaging, the ability to obtain broad bandpass X- species R lines can be tracked in extensive samples. The ca- ray spectra and to localise and characterise the high-energy pability to cover the redshift range from 0.07

Fig. 23 Observer frame peak energy versus bolometric flux of GRBs Fig. 24 The annual rate of GRBs predicted for THESEUS SXI (red) with well constrained redshifts and spectra detected by various mis- compared to Swift (blue). The upper scale shows the age of the Uni- sions with a cloud of points from GRB population simulations verse. For Swift the actual number of known redshifts is approximately (Ghirlanda et al. 2015). Yellow points are those at z>5 The use of a one third that plotted and none were determined on board (the blue softer X-ray band permits the detection of GRBs with lower fluence curve has been linearly scaled upwards to match the total Swift trig- and hence enhances the detection of higher redshift objects. ger rate). For THESEUS the red region uses the simulations from Ghirlanda et al. (2015) and adopts the expected sensitivity for the SXI and XGIS instruments. both imaging and spectroscopic capability (the IRT). The spacecraft needs to be agile (fast response to enable the IRT to detect the source) and be able to rapidly communicate Swift discovered GRBs have redshifts, all determined from triggers to the ground so as to enable other observatories to the ground). The predicted annual rate of GRB detections by also follow-up the new transients. The ability to point the THESEUS SXI is 300-700 per year, with a very high (>5- spacecraft into the night sky (anti-solar) direction for part 10) increased rate relative to Swift at the highest redshifts. of the orbit enhances rapid ground follow-up capability to As discussed below in the section on IR follow-up, imag- provide additional (multi-wavelength) data. Capability for ing and photometric redshifts will be obtained on-board for stable 3-axis pointing for >1 ksec is required to detect the the highest redshift GRBs and spectroscopic redshifts for longest duration transients. the majority. For those GRBs detected on board but without spectroscopy triggers sent to ground, ground-based telescopes can be used to obtain spectra - giving priority to 3.1 Wide field monitoring in soft X-rays with deep those with photometric indication of high redshift. THE- sensitivity SEUS alone will obtain more spectroscopic redshifts on board in a year than Swift has provided in a decade. The search for To greatly increase the rate of GRB detection at high red- high-z GRBs is part of a more general unprecedentedly deep shifts and detect large numbers of other transients while si- monitoring of the X-ray transient Universe, whose motiva- multaneously providing accurate localisations requires the tion have been detailed in previous sections. The predicted provision of a large field-of-view soft X-ray imaging in- rate of detection of electromagnetic counterparts of GW sig- strument (see Sect. 4.1). We have performed simulations nals and of other transient and variable source types during (Ghirlanda et al. 2015) which show the scientific goals can the survey is shown in Table 1 and 2. The very large detec- be met with an instrument field of view of 1 sr, a sensitiv- tion rate of other transient types is due to the high sensitivity −10 −2 −1 ity in 1000 s of 10 erg cm s (0.3-6 keV) and imag- of THESEUS. This is illustrated in Fig. 4, where the source ing capability sufficient to provide 0.5-1 arcmin localisations detection sensitivity of the proposed SXI and XGIS instru- (2 arcmin worst case at 90% c.l.; this requires a PSF FWHM ments are plotted verses integration time and overlaid are 4.5 arcmin). various sources types. Multiple timescale software triggers are required to find the range of flux versus duration transient events. Using such an instrument (the THESEUS SXI) and taking into account 3.2 Provision of broad-band X-ray spectroscopy the soft X-ray background, Fig. 23 shows the expected annual rate of GRBs as a function of redshift. Also plotted is The scientific objectives of THESEUS require the secure the rate of GRBs found by Swift (where the redshift dis- identification of sources types, in particular GRB triggers. tribution has been linearly scaled up based on those with The soft X-ray instrument is the primary source locator and redshift determinations - only approximately one third of has a high sensitivity to a wide variety of source types, as THESEUS 27 discussed above, as required to achieve the scientific goals. Table 3 THESEUS yearly detection and redshift measurements rates. This instrument will trigger on a large number of known The redshift measurements indicated are those that would be achieved sources which should not result in a spacecraft slew, but directly on-board and do not include refined and/or additional measurements on-ground (as it is currently done for other observatories as also other transient sources only some of which are GRBs. Swift). Note that photometric redshifts are possible only at z&5, when To reliably identify GRBs as well as spectroscopically char- the Lyman “dropout” or “break” gets inside the IRT band. acterise other sources and reduce the number of demanded THESEUS GRB/yr All z>5 z>8 z>10 slews requires the provision of a sensitive broad-band X- gamma ray instrument well matched to the sensitivity of the Detections 387-870 25-60 4-10 2-4 soft X-ray instrument and with source location capabilities Photometric z 25-60 4-10 2-4 Spectroscopic z 156-350 10-20 1-3 0.5-1 of a few arcmin in the X-ray energy band. To meet the scientific goals we require an instrument with the following characteristics: The requirement number 1 is justified by the fact that the – extend the soft X-ray band of the imaging instrument up goal of the THESEUS mission is to study the Universe at to the MeV band; z > 6 in order to study the epoch of reionization. CMB ex- – identify and localize with a few arcmin accuracy the periments suggest that reionization was underway at z∼9, GRBs by providing simultaneous triggers and by provid- while it appears to be completed by z∼6.5. The question ing higher energy light curves and spectra to determine is whether massive stars could sustain a largely reionized the luminosity of the GRB; Universe at z=6-9, and beyond. GRB afterglow spectra are – reduce the demanded number of spacecraft slews to ob- power laws and, due to the Ly-alpha drop-out (i.e. the Lyman serve with the IRT and act as a crucial filter to reduce soft alpha absorption within the GRB host galaxies and inter- X-ray trigger volume for ground/space telescope follow- vening IGM), a very attenuated signal is expected at wave- up; lengths shorter than the Lyman alpha break, providing an – measure unbiased GRB/transient X- and gamma-ray spec- unmistakable feature. Due to cosmological expansion the tra down to short time scales (ms time scales for the Ly-alpha wavelength (1216 Å=0.126 µm) moves along the strongest events) to probe GRB physics. energy band, and in order to measure GRB redshifts between z=4 and z=10 the telescope detector has to be sensitive in the The proposed XGIS instrument provides the required sen- 0.7 to 1.8 µm range. GRBs with z<4 can be used as compar- sitivity and bandpass (Fig. 25). The sensitivity of the SXI ison to evaluate how massive stars evolve along the history and XGIS are well matched over the typical durations of of the Universe, and they can be easily followed up from GRBs (few to few tens of seconds). The XGIS will provide ground. It is for high redshift GRBs that a NIR telescope in spectroscopy over 2-20000 keV with monitoring timescales space really takes advantage of the absence of background down to milli-seconds. Despite advances during the Swift due to the atmosphere. The field of view of the IRT tele- and Fermi era to identify and characterise GRB phenomenon scope shall be larger than 4x4 arcmin, given that the SXI will requires study of the prompt emission. Planned future mis- provide error boxes which are at worst 2 arcmin (90% c.l.) sions (e.g. SVOM) do not provide the required combination radius. For requirement number 2 the telescope will be op- of sensitivity and bandpass. erated in low resolution mode (R∼10-20), and the Ly-alpha drop-off will be searched for. A fit of the sources’ low resolution spectra, done on-board, should be capable of identi- 3.3 Optical-IR follow-up fying high-redshift candidates. If we focus on GRBs at redshift larger than 6 the detector shall be optimized in terms The scientific goals of THESEUS require the following on- of QE the 0.8-1.5 µm wavelength range. To obtain reliable board capabilities for an optical/near IR telescope (IRT) to results the detector QE shall be known within 10-20%. The follow-up GRBs after a demanded spacecraft slew: requirement number 3 deals with the high-resolution spectra (R∼500). As shown in the left panel of Fig. 26, a resolution 1. Identify and localize the GRBs found by the SXI and of the order of R∼500 is good enough to identify the main XGIS to arcsecond accuracy in the visible and near IR absorption lines in bright GRB NIR afterglow spectra. Such domain (0.7-1.8 µm); detections would (i) enable a more precise measure of the 2. Autonomously determine the photometric redshift of GRBs GRB redshift, that goes beyond the “mere” detection of the for z>4 and provide redshift upper limits for those at Ly-alpha drop off achievable with lower resolution spectra lower redshift; and (ii) help in discriminating between highly-extinguished 3. Provide precise spectroscopic redshift measure for bright and high-redshift (z>5) events. Besides the redshift mea- GRBs, together with limits on the intrinsic NH and metal- sure, with the IR resolution spectroscopy it will be possible licity for the majority of GRBs at z>4. to derive limits on element relative abundances and metallic- 28 Amati et al.

Fig. 25 The left-hand panel shows the GRASP (FOV×Effective Area) of the THESEUS/SXI in the soft X-ray energy band compared to XMM- Newton and eROSITA. The GRASP of X-ray monitors on-board MAXI and ASTROSAT are also show for completeness, even though these are not focusing and their sensitivity for a given effective area is substantially sworse than that of focusing teelscopes. The leap in monitoring/survey of the soft X-ray sky allowed by THESEUS/SXI is outstanding. The right panel shows THESEUS/XGIS filling the parameter space in the top-left corner of the right-hand panel where other instruments have either too high an X-ray threshold or too low effective area, and will still provide 1000-1550 cm2 effective area up to several MeVs (Yonetoku et al. 2014).

Fig. 26 Left: a simulated IRT high resolution (R=500) spectrum for a GRB at z=6.3 observed at 1 hr post trigger assuming a GRB similar to GRB 050904. The spectrum has host log(NH)=21 and neutral fraction Fx=0.5 (and metallicity 0.1 solar). The two models are: Red: log(NH)=21.3, Fx=0 Green: log(NH)=20.3, Fx=1. The IRT spectra provide accurate redshifts. Right: simulated IRT low resolution (R=20) spectra as a function of redshift for a GRB at the limiting MAB=20.8 mag at z=10 (brighter bursts can be expected at this redshift), and by assuming a 20 min exposure. The underlying (noise-free) model spectra in each case are shown as smooth, dashed lines. Even for diﬃcult cases the low-res spectroscopy should provide redshifts to a few percent precision or better. For many applications this is ﬁne - e.g. star formation rate evolution.

ity (together with a measure of NH for the brightest events, The sensitivity of the SXI triggering system in the 0.3- obtained by fitting the red wing of the Ly-alpha). Such in- 6 keV energy band probes a fluence range of 10−8 and 10−9 formation will be vital to optimize ground-based follow-up erg cm−2. Based on (Ghirlanda et al. 2015) the proposed (with the large aperture facilities that will be available in THESEUS IRT with a limiting sensitivity of 20.6 mag in 2028, like ELT), aimed at precise optical/IR spectroscopic the H (1.6±0.15 µm) filter is expected to detect all the GRB studies for a detailed characterization of the GRB environ- counterparts in imaging and low-resolution spectroscopy, if ment throught the measure of chemical abundances, metal- pointed early after the GRB trigger, in a 300 s exposure, licity, and SFR. and for the large majority of GRBs high-resolution spectra THESEUS 29 can be taken even 1-2 hours after the GRB (first or second Table 4 SXI detector unit main physical characteristics. spacecraft orbit) with the 19th magnitude sensitivity IRT. Energy band (keV) 0.3-6 In Fig. 2 we show the rate of GRBs whose redshift will Telescope type Lobster eye Optics aperture 320×320 mm2 be spectroscopically determined by THESEUS on-board as Optics configuration 8×8 square pore MCPs a function of redshift. For the other GRBs detected by the MCP size 40×40 mm2 Focal length 300 mm SXI/XGIS, the IRT will provide a location and a redshift Focal plane shape spherical limit and thus provide a redshift estimate for the entire sam- Focal plane detectors CCD array Size of each CCD 81.2×67.7 mm2 ple detected on-board. The cumulative distribution repre- Pixel size 18 µm sents the rate (number of GRBs per year) that can be de- Number of pixel 4510×3758 per CCD Number of CCDs 4 tected by THESEUS (red solid filled region). The width of Field of View ∼1 sr the distribution accounts for the uncertainties of the popu- Angular accuracy (best, worst) (<10, 105) arcsec lation synthesis code adopted. For comparison, the rate of detection of GRBs by Swift is shown with a blue line. THE- SEUS out-performs Swift by about an order of magnitude at ments with the spacecraft (provided by a German led con- all redshifts and by more at the highest redshifts. Using the sortium and Poland). The general avionic block diagram of IRT to follow-up the SXI and XGIS will identify the high- the THESEUS PLM as well as SVM is shown in Fig. 42. est priority high-redshift targets for the early Universe science goals. This rate is derived from the actual population of GRBs detected by Swift and with measured redshift multi- 4.1 The Soft X-Ray Imager (SXI) plied by a factor of 3. Indeed, approximately only 1/3 of the GRBs detected by Swift have their redshift measured. The The THESEUS Soft X-ray Imager (SXI) comprises 4 detec- upper axis shows the age of the Universe (5 Lobster mod- tor units (DUs). Each DU is a wide field lobster eye tele- ules with focal length 300 mm and individual field of view scope using the optical principle first described by Angel 0.16 sr are assumed). The detection and redshift-estimate (1979) with an optical bench as shown in Fig. 27. annual rates expected form THESEUS are also summarized The optics aperture is formed by an array of 8×8 square in Table 3. pore Micro Channel Plates (MCPs). The MCPs are 40×40 mm2 and are mounted on a spherical frame with radius of curva- 4 Scientific instruments ture 600 mm (2 times the focal length of 300 mm). Table 4 summarizes the SXI characteristics. The mechanical enve- Following the scientific requirements described in the pre- lope of a SXI module has a square cross-section 320×320 mm2 vious section, the baseline Instrument suite configuration of at the optics end tapering to 200×200 mm2 at detector. The THESEUS payload includes 4 lobster-eye modules (F=300 mm),depth of the detector housing is 200 mm giving an over- a 70 cm class IR telescope and 3 X-ray/soft gamma-ray coded- all module length of 500 mm. The left-hand side of Fig. 28 mask cameras based on Si+CsI(Tl) coupling technology cov- shows the optics frame of the breadboard model for the SVOM ering twice the FOV of the lobster-eye modules. In sum- MXT lobster eye telescope which comprises 21 square MCPs mary, the scientific payload of THESEUS will be composed mounted over a 5×5 grid (the corners are unoccupied for of: this instrument). The front surface is spherical with radius of curvature 2000 mm giving a focal length of 1000 mm. The – Soft X-ray Imager (SXI): a set of 4 “Lobster-Eye” X- design proposed for SXI uses the same plate size and ex- ray (0.3-6 keV) telescopes covering a total FOV of ∼1 sr actly the same mounting principle but a shorter focal length, with 0.5-1 arcmin source location accuracy, provided by 300 mm, so the radius of curvature of the front surface must a UK led consortium; be 600 mm. The right-hand panels of Fig. 28 shows a schematic – InfraRed Telescope (IRT): a 70 cm class near-infrared of a single plate and a micrograph that reveals the square (up to 2 µm) telescope with imaging and moderate spec- pore glass structure. The focal plane of each SXI module is tral capabilities provided by a France led consortium (in- a spherical surface of radius of curvature 600 mm situated a cluding ESA, Switzerland, and Germany); distance 300 mm (the focal length) from the optics aperture. – X-Gamma ray Imaging Spectrometer (XGIS): a spec- The detectors for each module comprise a 2×2 array of large trometer comprising 3 detection units based on SDD+CsI(Tl) format detectors tilted to approximate to the spherical focal modules (2 keV-20 MeV), covering twice the FOV of the surface. SXI. This instrument will be provided by an Italian led consortium (including Spain). All instruments are equipped with an Instrument Data Calibration Handling Unit (I-DHU), interfacing each of the three instru- The following calibrations are envisaged: 30 Amati et al.

Fig. 27 The SXI block diagram concept (left) and optical elements (right).

– SXI optic: X-ray beam line testing to measure the focal count rate expected from the diffuse sky (Galactic and Cos- length, the effective area and the point spread function mic) and point sources. as a function of off-axis angle and energy. The sensitivity to transient sources using this background – SXI detector: Vacuum test facility to measure the gain rate and a false detection probability of 1.0×10−10 is shown and energy resolution as a function of energy. as a function of integration time in Fig. 4. For longer in- – SXI end-to-end: X-ray beam line facility confirm the fo- tegration times the source count required rises, e.g., to 30 cal length and measure the instrument effective area and counts for a 1 ks integration. We find that 94% of the Swift PSF as a function of photon energy and off-axis angle. BAT bursts (before 2010 September 16) would be detected – SXI in orbit calibration: use cosmic sources to confirm by the SXI. The X-ray light curve of the afterglow would be in-flight alignment, plate scale, point spread function, ef- detected to >1 ks after the trigger for a large fraction of the fective area, vignetting and energy resolution. A regular bursts. monitoring of cosmic sources is planned to verify the status and correctness of the instrument calibration. Trigger Algorithm The ideal algorithm would be some form of matched filter- SXI Performance, Sensitivity and Data Rate ing using the full PSF distribution but because of the extent The imaging area of the CCDs sets the field of view of each of the PSF this would be far too computationally heavy. At module. A compliment of 4 SXI modules has a total field the other extreme a simple scheme would be to search for of view of 3200 square degrees (0.9 sr). The point spread significant peaks using the cell size commensurate with the function is shown in Fig. 29. The inner dotted square shows central peak in the PSF. This would be faster but utilizes the off-axis angle at which the cross arms go to zero as de- only ∼25% of the total flux detected. The scheme described termined by the L/d ratio of the pores. For optimum perfor- below is a two stage process which exploits the cross-arm mance at 1 keV we require L/d=50. The outer dotted square geometry but avoids computationally expensive 2-D cross- indicates the shadowing of the cross-arms introduced by the correlation. For the 1st stage the focal plane is divided into gap between the individual MCPs in the aperture. The cen- square patches with angular side length ∼ 4d/L = 1/12 ra- tral true-focus spot is illustrated by the projection plot to the dians aligned with the cross-arm axes. The dotted central left. The FWHM is 4.5 arcmin and all the true-focus flux square shown in Fig. 31 indicates the size and orientation of is contained by a circular beam of diameter 10 arcmin. The such a patch. The optimum size of such patches depends on collecting area, within a 10 arcmin beam centered on the the HEW of the lobster-eye optic and the background count central focus, as a function of energy is shown in Fig. 30. rate. The patches could correspond to detector elements or The optics provides the area plotted in black. The red curve tiles in the focal plane, e.g. CCD arrays. The peak profile is includes the quantum efficiency of the CCD and the trans- the line spread profile of the central spot and cross-arms of mission of the optical blocking filter comprising a 60 nm the PSF. The remainder of the histogram distribution arises Aluminium film deposited over the front of the MCPs and from events in the cross-arm parallel to the histogram di- 260 nm of Aluminium plus 500 nm of parylene on the sur- rection, the diffuse component of the PSF and any diffuse face of the detectors. Because the angular width of the optics background events not associated with the source. Because MCP-array is 2.3 deg larger than the CCD-array the field of we are looking for transient sources the fixed pattern of the view is unvignetted at 1 keV and above so the collecting steady sources in the field of view at the time would have to area shown in Fig. 30 is constant across the field of view. be subtracted from the histogram distributions. As the point- Using the Rosat All-sky Survey data we can estimate the ing changes this fixed pattern background would have to be THESEUS 31

Fig. 28 Left: The SVOM MXT lobster eye optic aperture frame. Top right: A schematic of a single square pore MCP. Bottom right: A micrograph of a square pore MCP showing the pore structure. This plate has a pore size d=20 µm and a wall thickness w=6 µm.

The above considers a single value of ∆T. We envisage that a series of searches would be run in parallel each using a different integration time so that the sensitivity limit as a function of ∆T is covered. The basic scheme is illustrated in Fig. 31. The total source count assumed for this illustration was 40 spread over the full PSF as plotted in Fig. 29. The bin size used for the histograms was 1 arcmin, and the HEW of the central peak of the PSF is approximately 4 arcmins. We have tested the algorithm over a range of integration times and background conditions. It achieves the sensitivity limit plotted in the science requirements section. When a signif- Fig. 29 The point spread function of the SXI. icant transient peak is identified the position must be con- verted to sky coordinates using the current aspect solution (from Payload star trackers). Positions of all transients found updated. A transient source is detected if a significant peak must be cross-correlated with known source catalogues, e.g. is seen in both histograms. Rosat All-Sky Survey, Flare stars, Swift BAT catalogue etc. The sensitivity of detection and accuracy of the derived Any position which does not match a known position must position of the source within the patch depends on the bin be passed to the Space Craft as a potential trigger position. size of the histograms, the HEW of the central peak of the The processing required to implement the above is as PSF and the background. For the most sensitive detection follows: the bin size should be approximately equal to the HEW but this will limit the accuracy of the position. If the bin size of the histograms is chosen to be significantly smaller than the 1. Extract frames from the CCD at ∆T=2 s (this is the fastest width of the HEW then the histograms can be smoothed by rate set by the frame time). cross-correlation with the expected line width profile of the 2. Apply event reconstruction algorithm to the frames to peak-cross-arm combination. Using the smaller bin size the give an event list with positions in CCD pixels and a histograms can also be used to estimate the position centroid pulse height. of the source within the patch. The significance used for this 3. Convert the pixel positions into a local module coordi- first stage should be low, e.g. 2.5 σ. This will provide candi- nate frame which is aligned to the cross-arms of the PSF. date positions for the second stage. 4. Accumulate counts in the 1-D histograms. For each of the candidate positions identified in the first 5. Subtract the fixed source/background pattern from the stage a cross-arm patch is set up to cover just the detec- histograms. tor area which is expected to contain a fraction of the full 6. Scan the histograms for significant peaks and extract can- cross-arms and the central peak in the PSF. The cross-patch didate positions for further analysis. dimensions are changed depending on the integration time 7. Set up the cross-arm mask at candidate positions to look ∆T. For short integration times the total background count for significant peaks. Calculate an accurate position in will be small and the cross-patch size is set large to capture the local module coordinate frame for the peak. a large fraction of the counts from the cross-arms and central 8. Convert this position into global sky coordinates (quater- peak. nion). 32 Amati et al.

Fig. 30 Left: Collecting area as a function of energy (assuming a focal lenght of 300 mm and including the contributions of the central spot, the 2 cross-arms, and the straight through flux). The black line represents the optics only. The red curve includes the quantum efficiency of the CCD and the transmission of the optical blocking filter. Right: The position accuracy of the SXI as a function of source and background count. R90 is the error radius that contains 90% of the derived positions.

9. Check positions against on-board catalogues to weed out out of the scintillation light, while the other sides of the bar known sources. are wrapped with a light reflecting material conveying the 10. Communicate unidentified transients to the Spacecraft. scintillation light towards the PDs. The scintillator material is CsI(Tl) peaking its light emission at about 560 nm. The Note that points 4-7 above must be repeated for different ∆T PD is realized with the technique of Silicon Drift Detec- values (e.g., 2, 20, 200, 2000 s). tors (SDD-PD; Gatti and Rehak 1984) with an active area of 5×5 mm2 matching the scintillator cross section. Crys- tals are tightly packed in an array of 32×32 elements to 4.2 The X-Gamma ray Imaging Spectrometer (XGIS) form the module. The SDD and scintillator detect X- and The X-Gamma ray Imaging Spectrometer (XGIS) comprises gamma-rays. The operating principle (see Fig. 32 right) is 3 units (telescopes). The three units are pointed at offset di- the following. The top SDD-PD, facing the X-/gamma-ray rections in such a way that their FOV partially overlap. Each entrance window, is operated both as X-ray detector for low unit (Fig. 32 and Table 5) has imaging capabilities in the energy X-ray photons interacting in Silicon and as a read-out low energy band (2-30 keV) thanks to the combination of an system of the scintillation light resulting from X-/gamma- opaque mask superimposed to a position sensitive detector. ray interactions in the scintillator. The bottom SDD-PD at A passive shield placed on the mechanical structure between the other extreme of the crystal bar operates only as a read- the mask and the detector plane will determine the FOV out system for the scintillations. The discrimination between of the XGIS unit for X-rays up to about 150 keV energy. energy losses in Si and CsI is based on the different shape Furthermore the detector plane energy range is extended up of charge pulses. While the electron-hole pair creation from to 20 MeV without imaging capabilities. The main perfor- X-ray interaction in Silicon generates a fast signal (about mance of an XGIS unit are reported in Table 6. The detec- 10 ns rise time), the scintillation light collection is domi- tion plane of each unit is made of 4 detector modules each nated by the fluorescent states de-excitation time (0.68 µs, one about 195×195×50 mm in size detecting X and gamma 64%, and 3.34 µs, 36%, for CsI(Tl)) and a few µs shap- rays in the range 2 keV-20 MeV. For each energy loss in the ing time is needed in this case to avoid significant ballistic module, whatever procured by EM radiation or ionizing par- deficit. Pulse shape analysis (PSA) techniques are adopted ticle, the energy released, the 3 spatial coordinates and the to discriminate between signals due to energy losses in Si or energy deposit of the interaction and time of occurrence will CsI. The results we obtained for the separation of the energy 241 be recorded. losses in the case of an Am source (Marisaldi et al. 2004) The basic element of a module (Fig. 32) is a bar made are shown in Fig. 34. As can be seen from the left panel of scintillating crystal 5×5×30 mm3 in size. Each extreme of this figure, the ratio of the two pulse heights is approxi- of the bar is covered with a Photo Diode (PD) for the read- mately constant for pulses of common shape and allows dis- THESEUS 33

Fig. 31 The two stage trigger algorithm. Top left-hand panel: the detected event distribution ∆T=4 seconds and a source count rate of 40 cts s-1 over the full PSF. The cross-arms are rotated wrt the detector axes to demonstrate how this can be handled. Top right-hand panel: the detected event distribution in the patch of sky aligned to the cross-arm axes of the PSF (shown as the red rectangle in the top left-hand panel). The red cross-patch indicates the area used for the second stage of the algorithm. Bottom panels: the histograms along columns and rows in the patch.

Table 5 XGIS detector unit main physical characteristics.

Energy band 2 keV-20 MeV Detection plane modules 4 detector pixel/module 32×32 pixel size (= mask element size) 5×5 mm Low-energy detector (2-30 keV) Silicon Drift Detector 450 µm thick High energy detector (>30 keV) CsI(Tl) 3 cm thick Discrimination Si/CsI(Tl) detection Pulse shape analysis Dimension 50×50×85 cm Power 30.0 W Mass 37.3 kg

Table 6 XGIS unit characteristics vs energy range.

2-30 keV 30-150 keV >150 keV Fully coded FOV 9×9 deg2 Half sens. FOV 50×50 deg2 50×50 deg2 (FWHM) Total FOV 64×64 deg2 85×85 deg2 (FWZR) 2πsr Ang. res 25 arcmin Source location accuracy ∼5 arcmin (for >6 σ source) Energy res 200 eV FWHM at 6 keV 18% FWHM at 60 keV 6% FWHM at 500 keV Timing res. 1 µs 1 µs 1 µs On axis useful area 512 cm2 1024 cm2 1024 cm2 34 Amati et al.

Fig. 32 Left: Sketch of the XGIS Unit. Right: Principle of operation of the XGIS detection units: low-energy X-rays interact in Silicon, higher energy photons interact in the scintillator, providing an energy range covering three orders of magnitude. A pulse shape discriminator determines if the interaction has occurred in Si or in the crystal.

XGIS building blocks In the XGIS HW, the main building blocks (see Fig. 35 for one XGIS unit) are: 1. the mask and the FOV delimeter; 2. the scintillator detectors; 3. the FEE in both its analogue part (with SDD-PD, ASIC1 and ASIC2), digital part (DFEE) and services (TLM, TLC Power supply). The coded mask of each XGIS unit, placed 70 cm above the detector modules is made of stainless steel of 0.5 mm thick. The mask overall size is 50×50 cm and will have a pattern allowing self-support in order to guarantee the maximum transparency of the open elements. The mechanical structure connecting the mask with the detector is also made of stainless steel 0.1 mm thick and supports 4 Tungsten slats 45 cm high with a variable thickness (0.5-0.3 mm). This structure will act as a lateral passive shield for the imager system (1-30 keV) and as a FOV delimiter at energies >150 keV. In the latter range, the resulting FOV is 50×50 deg2 (FWHM) and 85×85 deg2 (FWZR). By combining the three units, Fig. 33 Sketch of the XGIS module. A module (right) is made of an with an offset of ±35 deg for two of them, the FOV delimiter array of 32×32 scintillator bars with Si PD read-out at both ends (left). guarantees an average XGIS effective area of ∼1400 cm2 in Both PD and scintillators are used as active detectors. The PDs readout 2 electronics consist of an ASIC pre-amp mounted near each PD’s anode the SXI FOV (104×31 deg ). while the rest of the processing chain is placed at the module sides and bottom. Data Handling Unit (DHU) and its functions The whole XGIS background data rate (3 units) towards the DHU is of the order of 6000 event/sec in the 2-30 keV range and about 3700 event/sec above 30 keV. Each event received crimination between interactions taking place in Silicon or by DHU will be identified with a word of 64 bits (4 for mod- in the scintillator. For gamma-rays interacting in the scintil- ule address, 10 for bar address, 10 for signal amplitude of lator, combining the signals from the two PDs at the extreme the fast top channel, 11 for signal amplitude of the slow top of each bar allows to determine the energy and the depth of channel, 11 for signal amplitude of the slow bottom channel, the interaction inside the crystal (Labanti et al. 2008). 18 for time). DHU functions will be: THESEUS 35

Fig. 34 Left: bidimensional spectrum of a 241Am source showing interaction in Silicon (top line) and in the scintillator (bottom line). Right: distribution of the ratio of the two processing chains for events in Silicon and in the scintillator. The large peak separation indicates the optimal discrimination performance.

– discriminates between Si and CsI events. uation of the significance of the count rate variation, cal- – For CsI events, evaluates the interaction position inside culated as described in the sub-section below. The pro- the bar by weighting the signals of the 2 PDs (a few mm cedure will be the following: resolution expected). Combining this information with – from the SXI direction given to the event, it is iden- the address of the bar (5×5 mm in size) each module tified one of the three XGIS units in which the event becomes a 3D position sensitive detector. has potentially been detected; – Exploiting the 3D capabilities background can be mini- – look for an excess of the rates in the modules of this mized. unit in the bands 2-30 keV and 30-200 keV with re- – It continuously calculates along the orbit the event rate spect to the average count-rate continuously calcu- of each module in different energy bands (typically 2- lated by DHU. 30 keV, 30-200 keV and >200 keV) and on 5 different 2. Autonomous XGIS GRB trigger based on data rate. The times scales (e.g., 1 ms, 10 ms, 100 ms, 1 s, and 10 s). autonomous GRB trigger for XGIS inherits the experi- – In the 2-30 keV range and for each unit, it produces im- ence acquired with the Gamma Ray Burst Monitor (GRBM) ages of the FOV in a defined integration time. aboard BeppoSAX and that acquired with the Mini-calorimeter – It holds in a memory buffer all the XGIS data, rates and aboard AGILE (Fuschino et al. 2008) and concerns all images of the last 100 s (typical) with respect to the cur- the modules of the 3 XGIS units. For each module the rent time. above energy intervals (2-30 and 30-200 keV) are con- – Produce maps of the three unit planes with event pixel sidered for the trigger. The mean count rate of each mod- by pixel histograms in different energy bands (typically ule in each of these bands is continuously evaluated on 32 with E width varying logarithmically) and with se- different time scales (e.g., 10 ms, 100 ms, 1 s, and 10 s). lectable integration times (min 1 s). A trigger condition is satisfied when, in one or both of these energy bands, at least a given fraction (typically XGIS and the GRB trigger system &3) of detection modules sees a simultaneous excess XGIS will contribute to the THESEUS’s GRB trigger sys- with a significance level of typically 5 σ on at least one tem in different ways: time scale with respect to the mean count rate. 3. Autonomous XGIS GRB trigger based on images. For 1. Qualification of the SXI triggers. The primary role of each XGIS unit, the 2-30 keV actual images will be con- XGIS is to qualify the SXI triggers as true GRB. The fronted with reference images derived averaging n (typi- basic algorithm for GRB validation is based on an eval- 36 Amati et al.

cally 30) previous images, and a spot emerging from the be implemented (similarly to what is done for the WFC3 on comparison at a significance level of 5 σ typically will board the Hubble Space Telescope), with the idea of mak- appear. If one of the above trigger condition is satisfied, ing use of the rest of the image to locate bright sources in event by event data, starting from 100 s before the trig- order to correct the frames a posteriori for the telescope jit- ger are transmitted to ground, the duration of this mode ter. The same goal could also be obtained by making use lasting until the counting rate becomes consistent with of the information provided by payload the high precision background level. star trackers mounted on the IRT. Hence the maximum limiting resolution that can be achieved by such a system for spectroscopy is limited to R∼500 for a sensitivity limit of Telemetry requirements about 17.5 (H, AB) considering a total integration time of For the study of transient or persistent sources different trans- 1800 s. The IRT expected performances are summarized in mission mode will be selected starting from the photon list Table 7. In order to achieve such performances (i.e., in con- and the histogram maps of the units. Typically the TLM load ditions such that thermal background represents less than will be maintained below 2 Gbit/orbit transmitting: (i) at low 20% of sky background) the telescope needs to be cooled at energies (<30 keV) pixel by pixel histograms in various En- 240±3 K, and this can be achieved by passive means. Con- ergy channels (e.g. 32 ch) with variable integration times cerning the IRT camera, the optics box needs to be cooled (e.g. 64 sec); (ii) above the 30 keV the whole photon list. to 190±5 K and the IR detector itself to 95±10 K: this al- In particular observations (e.g., crowded fields) a photon by lows the detector dark current to be kept at an acceptable photon transmission in the whole energy range will be se- level. The cooling of the detector at these low temperatures lected for a total maximum telemetry load of 3 Gbit/orbit. can hardly be achieved with a passive system in a low Earth In the case of a GRB trigger all the information available orbit such as the one foreseen for THESEUS, due to the ir- photon by photon is transmitted with a maximum telemetry radiation of the radiators of the infrared flux by the Earth at- load of 1 Gbit. mosphere. A TRL 5 cooling solution for space applications is represented by the use of a Miniature Pulse Tube Cooler XGIS sensitivity (MPTC). The 5 σ XGIS sensitivity for an integration of 1 s with en- In order to keep the camera design as simple as possi- ergy in the SXI FOV is shown in Fig. 36, along with the ble (e.g., avoiding to implement too many mechanisms, like XGIS flux sensitivity versus observation time at a signifi- tip-tilting mirrors, moving slits, etc.), we could implement cance of 5 σ in different energy ranges. In Fig. 37, the FOV a design with an intermediate focal plane making the inter- of the XGIS in the 2-30 keV band is compared with the SXI face between the telescope provided by ESA/industry and FOV, and the XGIS sensitivity vs. GRB peak energy is com- the IRT instrument provided by the consortium, as shown in pared with that of other instruments. the block diagram in Fig. 38. The focal plane instrument is composed by a spectral wheel and a filter wheel in which the ZYJH filters, a prism, and a volume phase holographic 4.3 The InfraRed Telescope (IRT) (VPH) grating will be mounted, in order to provide the expected scientific product (imaging, low and high-resolution The InfraRed Telescope (IRT) on board THESEUS is de- spectra of GRB afterglows and other transients). signed in order to identify, localize and study the transients Specifications of the entire system are given in Table 7. and especially the afterglows of the GRBs detected by the The mechanical envelope of IRT is a cylinder with 80 cm di- Soft X-ray Imager (SXI) and the X and Gamma Imaging ameter and 180 cm height. A sun-shield is placed on top of Spectrometer (XGIS). The telescope (optics and tube assem- the telescope baffle for IRT straylight protection. The ther- bly) can be made of SiC, a material that has been used in mal hardware is composed by a pulse tube cooling the De- other space missions (such as Gaia, Herschel, Sentinel2 and tector and FEE electronics and a set of thermal straps ex- SPICA study). Simulations using a 0.7 m aperture Cassegrain tracting the heat from the electronic boxes and camera op- space borne NIR telescope (with a 0.23 m secondary mirror tics coupled to a radiator located on the spacecraft structure. and a 10×10 arcmin imaging flied of view), using a space The overall telescope mass is 112.6 kg and the total power qualified Teledyne Hawaii-2RG (2048×2048 pixels) HgCdTe supply is 95 W. detector (18 µm/pixels, resulting in 0.3 arcsec/pix plate scale) show that for a 20.6 (H, AB) point like source and 300 s in- IRT Observing sequence tegration time one could expect a SNR of ∼5. The telescope The IRT observing sequence is as follow: sensitivity is limited by the platform jitter. In addition, due to the APE capability of the platform (2 arcmin), the high reso- 1. The IRT will observe the GRB error box in imaging lution spectroscopy mode cannot make use of a fine slit, and mode as soon as the satellite is stabilized within 1 arcsec. a slit-less mode over a 5×5 arcmin area of the detector will Three initial frames in the ZJH-bands will be taken (10 s THESEUS 37

Fig. 35 XGIS unit main building blocks.

Fig. 36 Left: XGIS sensitivity vs. energy for an integration of 1 s. Right: XGIS sensitivity as a function of exposure time in diﬀerent energy bands.

Fig. 37 Left: fractional variation of the effective area in the FOV of the XGIS. Right: Sensitivity of the XGIS to GRBs in terms of minimum detectable photon peak flux in 1s (5 σ) in the 1-1000 keV energy band as a function of the spectral peak energy (a method proposed by Band 2003). As can be seen, the combination of large effective area and unprecedented large energy band provides a much higher sensitivity w/r to previous (e.g., CGRO/BATSE), present (e.g., Swift/BAT) and next future (e.g., SVOM/ECLAIRS) in the soft energy range, while keeping a very good sensitivity up to the MeV range.

each, goal 19 AB 5 σ sensitivity limit in H) to estab- 3. Sources with peculiar colours and/or variability (such as lish the astrometry and determine the detected sources GRB afterglows) should have been pinpointed while the colours. low-res spectra were obtained and IRT will take a deeper 2. IRT will enter the spectroscopy mode (Low Resolution (20 mag sensitivity limit (AB)) H-band image for a to- Spectra, LRS) for a total integration time of 5 min (ex- tal of 60 s. These images will be then added/subtracted pected 5 σ sensitivity limit in H 18.5 (AB)). on board in order to identify bright variable sources with 38 Amati et al.

Table 7 IRT speciﬁcations.

Telescope type Cassegrain Primary and Secondary size 700 mm & 230 mm Material SiC (for both optics and optical tube assembly) Detector type Teledyne Hawaii-2RG 2048×2048 pixels (18 µm each) Imaging plate scale 0”.3/pixel Field of view 10×10 arcmin 10×10 arcmin 5×5 arcmin Resolution (λ/∆λ) 2-3 (imaging) 20 (low-res) 500 (high-res), goal 1000 Sensitivity (AB mag) H = 20.6 (300 s) H = 18.5 (300 s) H = 17.5 (1800 s) Filters ZYJH Prism VPH grating Wavelength range 0.7-1.8 µm (imaging) 0.7-1.8 µm (low-res) 0.7-1.8 µm (high-res, TBC) Total envelope size 800 (diameter) ×1800 mm Power 115 W (50 W for thermal control) Mass 112.6 kg

final correct reconstruction of the spectra by limiting the blurring effects. – In case that a faint (>17.5 H (AB)) variable source is found, IRT computes its redshift from the low resolution spectra, determines its position and sends both information to the ground (as for 3a). In this case IRT does not ask for a slew to the platform and stays in imaging mode for a 3600 s time interval to establish the GRB photometric light curve (covering any possible flaring) and leading the light curve to be known with an accuracy of <5%. Fig. 38 The IRT Telescope block diagram concept.

4.4 The Instrument Data Handling Units (I-DHUs) one of them possibly matching one of the peculiar colour ones. NIR catalogues will also be used in order to ex- Following the concept behind the organization of the THE- clude known sources from the GRB candidates. SEUS instruments as well as the decentralized avionic scheme, – In case a peculiar colour source or/and bright (<17.5 each of the three instrument payloads will be equipped with H (AB)) variable source is found in the imaging step, a dedicated Instrument Data Handling Unit (I-DHU) that the IRT computes its redshift (a numerical value if will serve as their TM/TC and power interface to the space- 5

Fig. 39 Left: the IRT focal plane division. The blue area (10×10 arcmin) is used for imaging and low resolution spectra. The orange area (5×5 arcmin) is used for high-resolution slit-less spectra. The size of the high-resolution spectral area is limited by the satellite pointing capabilities. Right: Teledyne Hawaii 2RG detector at ESA Payload Technology Validation section during the tests for the NISP instrument on board the EUCLID mission (Credits ESA).

– collect, process and store the data stream of the respec- cessing, formatting. The software will be designed in order tive instrument; to allow the instrument to have the complex functionality – implement the burst trigger algorithm on SXI and XGIS that it requires to allow itself to be updated and work around data; problems automatically and with input from the ground. There – implement the IRT burst follow up observation. will be a common software that is the same for all I-DHUs and an extended software part with modules specific for a The I-DHU consists of two main boards that are mounted given instrument. An example of a software module com- inside an aluminum case. In addition, each board exists in a mon to all I-DHUs is the determination of the location of a cold redundant (identical, non operating) version inside the burst or transient event. The time and location of the tran- box, that can replace the nominal board in case of a failure. sient will be transmitted to ground using the on-board VHF Switching between the nominal and redundant chain is done system in a <1 kbit message. The design of the trigger soft- from ground via a dedicated flight-proven circuitry. ware benefits from the heritage of the SVOM mission con- At the heart of the I-DHU design is the Processor Board. cept as well as past team experience on similar systems on It hosts the central CPU, the mass memory, time synchro- BeppoSAX, HETE-2, AGILE as well as the INTEGRAL nization and distribution circuits and the HK/health moni- burst alert system. toring acquisition chain. The Processor Board is connected Instrument control will be possible through the software to the spacecraft via one SpaceWire link through which it via telecommands from the ground (e.g., power on & off will receive the telecommands (TC) and send the science for individual units, loading parameters for processing & and HK/health data. On the other hand, the I-DHU is con- on-board calibration, investigations) and autonomously on- nected via another Spacewire link to the respective instru- board (e.g., mode switching, FDIR and diagnostic data col- ment to relay the TCs and acquire the science and HK data. lection). The software will implement the standard ECSS- The SpaceWire interface communication is handled directly style PUS service telecommand packets for housekeeping, through the main CPU (description see below), via its ex- memory maintenance, monitoring etc. and some standard isting dedicated hardware interfaces. The CPU is running an telemetry packets for command acceptance, housekeeping, RTEMS (Real Time Executive Management System), an op- event reporting, memory management, time management, eration system (OS) on which the individual software tasks science data etc. The software will be able to send setup (detailed description below) of this I-DHU will be run in information to the instrument and receive and process the parallel. Dedicated circuitry is foreseen on the Processor housekeeping data coming back and organize these data in a Board for the collection, digitization and organization of HK configurable way for a lower rate transmission to the ground. and health data from various voltage, current and temper- Figure 40 shows the commandable operational modes man- ature sensors. This will reduce the HK tasks on the main aged by the I-DHU. CPU, leaving only the science meta data (like rate meters, counters) and dedicated instrument data processing to be done there. The Processor Board will be developed by the 4.5 The Trigger Broadcasting Unit (TBU) IAAT in Tubingen,¨ Germany. The Power Board within the I- DHU will be developed by the Centrum Badan Kosmicznych, In case of trigger event it is necessary to provide the trigger Poland. It will generate the voltages for the Processor Board data to ground in a short time. It is expected triggered events and distribute the power to the instrument. occurred at the rate of one event per orbit and the data to be The main functions of the I-DHU on-board software are: sent to ground is very low: the amount is <1 kb/trigger event. instrument control, health monitoring and science data pro- To support the prompt transmission of such event data to 40 Amati et al.

Fig. 40 Overview of the I-DHU operation modes and transitions. ground segment it is necessary a link with Earth independent from the satellite TT&C, which can have a link with ground station only once per orbit. The solutions evaluated for an independent and prompt burst position broadcast to ground are by the means of: – VHF equatorial network (SVOM and HETE-2); – Orbcom satellite network (implemented in Agile satellite); – Iridium satellite network (tested by INAF/IASF on baloon Fig. 41 General block diagram of the Trigger Broadcast Unit. and ready to be tested in FEES/IOD n-sat); – TDRSS link. to which they are connected by means of a structural pedestals. The preferred solution is the well proven VHF broacast- The Instrument DUs mechanical fixing to this structure will ing based in the utilization of the SVOM equatorial net- be designed in order to guarantee thermo-structural decou- work. Link with SVOM ground segment will be made of 40 pling from the rest of satellite. The Service Module contains ground stations located around the Earth inside a ±30 deg all the platform subsystems and provides the mechanical in- strip. The satellite to SVOM network link shall be carry terface with the Launcher. Figure 42 shows the spacecraft out by the Trigger Broadcasting Unit (TBU, see Fig. 41) baseline configuration. proposed in the baseline as a unit of the Payload Module. The Payload Module is constructed around the IRT in- The antennas are miniaturised for a better accommodation strument, which is partially embedded inside the PLM struc- on PLM and SVM. The VHF ground network is the same ture and aligned with respect the S/C symmetry axis. The of SVOM mission, extensively described in the ground seg- module top plane is the mounting base of the other instrument section. For the definition of the VHF frequency range ments DUs (SXI and XGIS) which are distributed around a possible choice, according to ITU Article 5, could be 137- the IRT axis in order to minimize the satellite Moment of In- 137.175 MHz, reserved to space research. This band sub- ertia (MoI) but also to support efficient load transfer from the system for trigger transmission is consequently proposed for spacecraft to the launch vehicle, respecting their accommo- compatibility with SVOM ground segment. dation constraints and thermal requirements. The IRT LoS is the reference of the overall payload. The telescope is protected from straylight by a baffle; the profile of the baffle de- 5 Satellite configuration and mission profile fines the position of the entrance window plane of the other instruments. The 4 SXI DUs are nominally mounted on the The satellite configuration and design take into account a opposite side of the solar panels in order to keep them in the modular approach. The spacecraft platform is divided in two coldest side of the satellite and to have the largest area of modules, the Payload Module (PLM) and Service Module the observable sky when THESEUS lies between Sun and (SVM). The Payload Module will mechanically support the Earth. The SXI DUs positions and orientations are deter- Instruments DUs (SXI, XGIS and IRT) and will host inter- mined in such a way that no X-rays reflected by IRT tube or nally the Instruments ICUs. The instruments SXI and XGIS any other satellite structure can enter into SXI FOV. The 3 DUs are accommodated externally on the Payload Module XGIS units are tilted in such a way that the FOV of the units THESEUS 41

Fig. 42 THESEUS Satellite Baseline Configuration and Instrument suite accommodation. partially overlap. The resulting overall FOV (i.e., that of the Table 8 Summary of Instrument Suite temperatures. combination of the 3 units) covers and center the FOV of the Instrument Element Operative range (C) Cooling 4 SXI modules. The proposed accommodation is shown in SXI- structure/optics (-20, +20) passive Fig. 43. This configuration guarantees the required nominal SXI- detectors -65 active SXI, XGIS and IRT Field of view combination (REQ-MIS- XGIS-detectors (-20, +10) passive 050). Solar array proposed baseline consists of modular pan- IRT-structure -30 active IRT-optics -83 active els in fixed configuration, the panels are composed of a photovoltaic module and a mechanical on which photovoltaic module is mounted. At the level of the payload module top The AOCS subsystem will provide the required attitudes plane a Sun shield is mounted, in order to protect the in- to support the payload observation requirements, guarantee- struments from solar radiation. The structure of the Payload ing: module is provided of reinforcing shear panels and of an internal cylinder for the IRT telescope and detector accom- – the satellite agility with: modation. The internal cylinder has the function of struc- – fast slewing (.60 deg/10 min) for IRT LoS pointing tural support and it provides also a thermal separation for to the direction of GRBs and other transient of inter- IRT instrument from the rest of the module. In order to as- est for low resolution spectra; sure radiative thermal decoupling, the telescope is covered – fine slewing inside the IRT full FoV to achieve the by multi-layer insulation. IRT LoS fine pointing necessary for IR high resolution spectra. At the level of focal plane of IRT, where the Detector – the satellite pointing requirements are those of REQ- is placed, a Miniature Pulse Tube Cooler (MPTC) system MIS-060. is provided, acting with a heat-pipe system and a dedicated radiator. Dedicated radiator is provided also for each of the The subsystem is made up by software, running on the on other instruments (SXI and XIGS) on the pedestals. Every board computer, and by a set of sensors and actuators. ACS radiator is positioned on the own support structure of the sin- software is organised in operative stati, each of them ded- gle instrument. The Service module is currently conceived icated to the execution of a different mission task. The 3- as composed by a single module accommodating all the plat- axis stabilized attitude control is based on a set of 4 reaction form units (with the exception of one boresight star tracker wheels used in zero momentum mode and 3 magnetic tor- which is integrated on the IRT telescope tube to minimize quers mainly aimed to perform wheels desaturation. Sensors relative misalignment improving pointing knowledge per- used to reach the required attitude knowledge consist in star formances. In addition to the platform star tracker, two star sensors and fine rate sensors; in addition magnetometers and trackers hare foreseen in support to IRT instrument, to allow a set of solar sensors are available to cover all the mission astrometric measurements independent from the system. needs. 42 Amati et al.

instruments. The mission has been evaluated assuming as baseline a launch with Vega-C. The THESEUS satellite will be equipped with a suite of three instruments: SXI, XGIS and IRT. In summary the THESEUS satellite will be capable to: – to monitor a large sky sector for detecting, identifying and localizing likely transients/burst in the SXI and XGIS FOV; – of promptly (within a few tens of seconds at most) transmitting to ground the trigger time and position of GRBs and other transients of interest; – of autonomous (via SXI, XGIS or IRT trigger) orientation in the sky direction of interest; – to perform long observation of the sky direction of interest.

Fig. 43 THESEUS accommodation within VEGA C fairing. THESEUS requires a 3-axis stabilized attitude. During its orbital period THESEUS will have distinct operational modes: – Survey (burst hunting) mode: relevant to normal oper- The algorithms implemented in the ACS SW will pro- ation when SXI and XGIS are searching for transients. cess the sensors data in order to apply a proper control able The accessible sky for this kind of operation will be de- to guarantee the required pointing accuracy and stability. termined by the requirement that: – THESEUS will have a Field of Regards (FoR) defin- The THESEUS Telemetry and Telecommand subsystem ing the fraction of sky which can be monitored of includes a X-band TM/TC link between S/C and Earth for 64%. standard S/C operations in charge of the RF links with ground – When monitoring the sky in normal operations, the stations with Uplinks for satellite telecommands (TC) and number of re-pointings per orbit will be of the or- Downlinks for satellite telemetries (TM) and the ranging der of 3, resulting in observations with the SXI and function to allow range measurements. During downlink op- XGIS of about the whole FoR every 3 orbits. erations, stored data, read and formatted within the PDHU, – Burst mode: after detecting a GRB or other transient of are transmitted towards the X-Band transmission assembly, interest, the satellite is triggered to this mode by SXI where modulation, up conversion to X-Band and power am- and/or XGIS which transmit to satellite computer the plification will be executed. The X-Band antenna assembly quaternion of the area of interest. The satellite will au- will provide for transmission to the receiving ground station. tonomously fast repoint to place the transient within the The Thermal Control System (TCS) of the platform can field of view of the IRT according to the following steps: be implemented following a standard approach. It is mainly fast slewing (.60 deg/10 min) for IRT LoS pointing to of passive type, based on the capability of dissipating the in- the direction of GRBs and other transient of interest for ternal generated thermal power through radiators, where the low resolution spectra, satellite stabilization (RPE) within heat is conducted and emitted to deep space. As general ther- less than 0.5 arcsec fast data link for GRB coordinate mal control philosophy, all surfaces thermo-optical prop- communication to ground within a few min. erties are controlled by means of paints, multi layer blan- – Follow-up mode: the IRT shall observes inside the full kets and/or materials with well-known characteristics. High FoV of 10×10 arcmin the target with the pre-scripted emissivity coatings (black paint) are used for the spacecraft imaging spectroscopy sequence. In case of IRT high res- interior in order to uniformly distribute the generated power olution spectra acquisition a further satellite fine slewing and to avoid hot spots. Lateral closing panels having the (based on IRT source localization) shall be activated to function of radiators are covered with adequate coatings (e.g. place the IRT LoS inside a reduced FoV of 5×5 arcmin. white paint) to optimize the heat rejection to the space. The XGIS and SXI are in specific follow-up data acquisi- TCS service to Instrument Suite will consider the temper- tion mode. In this mode the GRB observation shall be atures summarized in Table 8. Detailed thermal and orbital performed in a time of 30 min. After completion of the analyses will optimize the thermal design. THESEUS satel- transient observation, THESEUS will return to Survey lite will operate in a low equatorial orbit (altitude <600 km, Mode to monitor the sky. inclination <5 deg). This orbital configuration will guaran- – IRT observatory mode: the IRT may be used as an obser- tee a low and stable background level in the high-energy vatory for pre-selected targets through a GO programme, THESEUS 43

Fig. 44 THESEUS Orbit Conﬁguration (Left) and THESEUS Orbit Ground Track (Right).

driving the pointing of the satellite. XGIS and SXI are of the mission will take advantage of the heritage gained observing as in survey mode, with the possibility of trig- through the Swift mission. The science observation plan will gering the burst mode be modified for Target of Opportunities (ToOs) coming pri- No specific orbit parameter change is required during the marily from the XGIS and SXI transient event detections, mission lifetime. THESEUS mission can be supported as but additional triggers can also be raised by other observato- baseline by a dedicated ground station located in Malindi ries at any wavelength. The mission will be designed to au- (3 deg S, 40 deg E). Another ground station, located in Al- tomatically repoint all classes of selected events detected by cantara (2 deg S, 4 deg W), is supposed as possible back- the SXI or the XGIS within minutes from the trigger. Longer up in case of Brasilian participation. In conformity with the reaction times are expected for external triggers. For non- selected equatorial orbit, both stations will allow highly fre- GRB targets, a significant part of the traditional ToOs will quent accesses to the satellite by a contact per orbit. Con- be pre-proposed as part of the calls for observing propos- tact analysis between the satellite and the ground stations als (i.e., Announcement of Opportunities, AOs). The pro- has been performed considering a minimum station eleva- posal will include trigger criteria, plus planning information tion angle over local horizon of 10 deg. like coordinates, exposure times, instruments observational modes, etc. Also, ToO proposals can be made to the SOC for an observation of a target outside the AO process us- 6 Scientific operations, quick-look activities and data ing the so-called Directors Discretionary Time (DDT). It is distribution expected that the THESEUS Launch and Early Operations Phase (LEOP) will be concluded with the successful injec- THESEUS being a GRB mission, it is expected that the tion into the chosen orbit. During Commissioning Phase the SOC will take care of nominal routine mission observation instruments will gradually be configured to operating status, planning with personnel in shift 7 days a week, 365 days with end-to-end test of functionality of systems without re- per year. Starting with the list of successful proposals sub- lying on the cosmic X-ray signals. The planning cycles, up- mitted at each yearly released announcement of opportu- and down-link functionality will be commissioned and the nity, a long-term planning schedule is created using the stan- basic instrument modes exercised. Scientific commission- dard science planning utilities. The core of the THESEUS ing and basic calibration verification will be completed with observing program is, however, expected to be dominated selected targets, including pointing and sensitivity stabil- by the follow-up of the detected GRB and other transient ity demonstrations. During Performance Verification Phase events. Therefore, detailed planning constraints (e.g., sky (PV) selected targets will be observed to instruments capa- visibility, and mission resources such as power and teleme- bilities, together with ToO, burst alert and ground segment try) will need to be identified by the SOC on a daily time capability confirmation. It is anticipated that normal science scale in order to shape the short term observational schedule. operations of the first Announcement of Opportunity (AO) Payload operations exclusion windows, on-board resources and the Guaranteed Time Observations (GTO) targets will envelopes for payload operations and final detailed checks start after 6 months when satisfactory performance has been against mission, environmental and resource constraints will demonstrated. have to be defined by the MOC on a similar timescale. The basic Mission Planning approach for all the routine science During normal science operations the data from the space- operations phases will be built on the experience of previ- craft (excluding the short alert messages broadcasted from ous missions, such as XMM-Newton, Herschel and INTE- the TBAS - THESEUS burst alert system - through the TBAGS GRAL. The rapid rescheduling imposed by the GRB nature - THESEUS burst alert ground segment) is received at the 44 Amati et al.

Complete author list and aﬃliations

C. Adami, Aix-Marseille Univ., CNRS, LAM, Laboratoire dAstro- physique de Marseille, 13388 Marseille, France; L. Amati, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, Italy; A. Antonelli, ASDC, Via del Politecnico snc - 00133 Rome, Italy; A. Argan, INAF-IAPS-Roma via Fosso del Cavaliere, 100, 00133, Rome, Italy; J.-L. Atteia, IRAP, Universite´ de Toulouse, CNRS, UPS, CNES, Toulouse, France; P. Attina, GP Advanced Projects, Italy; N. Auricchio, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, Italy; Z. Bagoly,Eotv¨ os¨ University, Budapest, Hungary; L. Balazs, MTA CSFK Konkoly Observatory, Konkoly-Thege M. ut´ Fig. 45 Schematic view of the Sun (SAA1) and Earh (SAA2) avoid- 13-17, Budapest, 1121, Hungary; ance angles for the expected orbit of THESEUS; the resulting Field of G. Baldazzi, INFN - Sezione di Bologna, Viale Berti Pichat 6/2, I- Regard (FoR) is 67% of the full sky. 40127 Bologna, Italy; Department of Physics, University of Bologna, Viale Berti Pichat 6/2, I-40127 Bologna, Italy; S. Basa, Aix-Marseille Univ., CNRS, LAM, Laboratoire dAstrophysique de Marseille, 13388 Marseille, France; MOC and sent in real time to the SOC where they are au- R. Basak, The Oskar Klein Centre for Cosmoparticle Physics, Al- tomatically processed into the lower level manageable FITS baNova, SE-106 91 Stockholm, Sweden; Department of Physics, KTH Royal Institute of Technology, AlbaNova University Center, SE-106 event files (including all relevant auxiliary files). Higer level 91 Stockholm, Sweden; data, including a set of pre-defined scientific products to be P. Bellutti, FBK, via Sommarive, 18, 38123 Povo, Trento, Italy; used for quick-look activities, are produced by a consortium- M. G. Bernardini, INAF - Osservatorio astronomico di Brera, Via E. led Science Data Center (SDC). Data collected during the Bianchi 46, Merate (LC), I-23807, Italy; G. Bertuccio, Politecnico di Milano, Via Anzani 42, I-22100, Como, 6 months of the PV phase will be made public only after Italy; INFN Milano, Via Celoria 16, I-20133, Milano, Italy; the validation of the SDC and the instrument operation cen- F. Bianco, Center for Cosmology and Particle Physics, New York Uni- ters, who lead the performance and health verification of versity, 4 Washington Place, New York, NY 10003, USA; the THESEUS instrument (together with calibration activ- A. Blain, Department of Physics and Astronomy, University of Leices- ter, Leicester LE1 7RH, UK; ities, supported by the SOC). All THESEUS data will be S. Boci, Department of Physics, University of Tirana, Tirana, Albania; made promptly accessible to the community on a centralized M. Boer, ARTEMIS, CNRS UMR 5270, Universite´ Coteˆ d’Azur, Ob- archive (THESEUS science data archive, TSDA) as soon as servatoire de la Coteˆ d’Azur, boulevard de l’Observatoire, CS 34229, they have been processed. The Swift and Fermi experience F-06304 Nice Cedex 04, France; M. T. Botticella, INAF - Capodimonte Astronomical observatory Naples, demonstrated that this strategy helps in maximizing the sci- Via Moiariello 16 I-80131, Naples, Italy; entific usage of the data, and is anyway mandated by the ur- E. Bozzo, Department of Astronomy, University of Geneva, ch. d’Ecogia´ gency of time-domain astrophysics. The centralized archive, 16, CH-1290 Versoix, Switzerland; to be hosted at SOC, will thus the primary repository for the O. Boulade, IRFU/Departement´ d’Astrophysique, CEA, Universite´ Paris- Saclay, F-91191, Gif-sur-Yvette, France; science data products of all levels, and will be used as the J. Braga, INPE, Av. dos Astronautas 1758, 12227-010, S.J.Campos- central “hub” during all phases of the mission. It will also SP, Brazil; guarantee the long term exploitability of the mission her- M. Branchesi, Universit degli Studi di Urbino Carlo Bo, via A. Saffi itage. The alerts provided by the THESEUS on-board detec- 2, 61029, Urbino; INFN, Sezione di Firenze, via G. Sansone 1, 50019, Sesto Fiorentino, Italy; tion and localization system will be monitored and analyzed S. Brandt, DTU Space - National Space Institute Elektrovej, Building by a dedicated alert center, but also distributed to the inter- 327, DK-2800 Kongens Lyngby, Denmark; ested community immediately after the PV phase. Relevant M. Briggs, Center for Space Plasma and Aeronomic Research, Uni- events discovered in the THESEUS data will be eventually versity of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805, USA; communicated by the SDC to the community through As- E. Brocato, INAF - Astronomico di Teramo, Mentore Maggini s.n.c., tronomer Telegrams or GCNs. 64100 Teramo, Italy; C. Budtz-Jorgensen, DTU Space - National Space Institute Elektro- vej, Building 327, DK-2800 Kongens Lyngby, Denmark; Acknowledgements S.E. acknowledges the financial support from con- A. Bulgarelli, INAF/IASF - Bologna, Via Gobetti 101, I-40129 Bologna, tracts ASI-INAF I/009/10/0, NARO15 ASI-INAF I/037/12/0 and ASI Italy; 2015-046-R.0. R.H. acknowledges GA CR grant 13-33324S. S.V. re- L. Burderi, Dipartimento di Fisica, Universita´ degli Studi di Cagliari, search leading to these results has received funding from the Euro- SP Monserrato-Sestu km 0.7, 09042 Monserrato, Italy; pean Union’s Seventh Framework Programme for research, technolog- C. Butler, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, ical development and demonstration under grant agreement no 606176. Italy; D.S. was supported by the Czech grant 16-01116S GA CR.ˇ P. Callanan, Department of Physics, University College Cork, Ireland; THESEUS 45

Fig. 46 The main THESEUS ground station Malindi is indicated, together with a possible sub-set of the SVOM VHF ground antennas needed to receive and broadcast the THESEUS alert messages generated on-board.

J. Camp, Astrophysics Science Division, Goddard Space Flight Cen- S. Covino, INAF-Brera Astronomical Observatory, Via Bianchi 46, ter, Greenbelt, Md 20771; 23807, Merate (LC), Italy; R. Campana, INAF/IASF-Bologna, via Piero Gobetti 101, I-40129, J.-G. Cuby, LAM, Laboratoire dAstrophysique de Marseille, 13388 Bologna, Italy; Marseille, France; S. Campana, INAF - Osservatorio astronomico di Brera, Via E. Bianchi P. D’Avanzo, INAF - Osservatorio astronomico di Brera, Via E. Bianchi 46, Merate (LC), I-23807, Italy; 46, Merate (LC), I-23807, Italy; E. Campolongo, OHB-Italia, Via Gallarate, 150 20151 Milano, ITALY; M. Dadina, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, F. Capitanio, INAF-IAPS-Roma via Fosso del Cavaliere, 100, 00133, Italy; Rome, Italy; M. G. Dainotti, Department of Physics & Astronomy, Stanford Uni- S. Capozziello, Dipartimento di Fisica, Universit di Napoli Federico versity, Via Pueblo Mall 382, Stanford CA, 94305-4060, USA; II, Via Cinthia, I-80126, Napoli, Italy; V. D’Elia, Space Science Data Center (SSDC), Agenzia Spaziale Ital- J. Caruana, Department of Physics, University of Malta, Msida MSD iana, via del Politecnico, s.n.c., I-00133, Roma, Italy; INAF-Osservatorio 2080, Malta; Institute of Space Sciences & Astronomy, University of Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone, Malta, Msida MSD 2080, Malta; Italy; P. Casella, INAF-Osservatorio Astronomico di Roma, Via Frascati 33, A. De Luca, INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica I-00040 Monte Porzio Catone, Italy; Milano, Via E. Bassini 15, I-20133 Milano, Italy; A. Castro-Tirado, IAA-CSIC, P.O. Box 03004, E-18080, Granada, D. De Martino, INAF - Capodimonte Astronomical observatory Naples, Spain; Via Moiariello 16 I-80131, Naples, Italy; B. Cenko, Astrophysics Science Division, NASA Goddard Space Flight M. De Pasquale, Department of Astronomy and Space Sciences, Is- Center, Mail Code 661, Greenbelt, MD 20771, USA; Joint Space-Science tanbul University, Beyazit, 34119, Istanbul, Turkey; Institute, University of Maryland, College Park, MD 20742, USA; E. Del Monte, INAF-IAPS-Roma via Fosso del Cavaliere, 100, 00133, A. Celotti, SISSA, via Bonomea 265, I-34136 Trieste, Italy; INAFOs- Rome, Italy; servatorio Astronomico di Brera, via Bianchi 46, I-23807 Merate (LC), M. Della Valle, INAF-Osservatorio Astronomico di Capodimonte, salita Italy; INFN - Sezione di Trieste, via Valerio 2, I-34127 Trieste, Italy; Moiariello 16, 80131, Napoli, Italy; International Center for Relativis- P. Chardonnet, LAPTh, Univ. de Savoie, CNRS, B.P. 110, Annecy-le- tic Astrophysics, Piazzale della Repubblica 2, 65122, Pescara, Italy; Vieux F-74941, France; National Research Nuclear University MEPhI, A. Drago, INFN, Via Enrico Fermi 40, Frascati, Italy; 31 Kashirskoe Sh., Moscow 115409, Russia; Y.-W. Dong, Institute of High Energy Physics, Beijing 100049, China; Y. Chen, Institute of High Energy Physics, Beijing 100049, China; G. Erdos, Wigner Research Centre for Physics, Hungarian Academy B. Ciardi, Max Planck Institute for Astrophysics, Karl-Schwarzschild- of Sciences, P.O. Box 49, H-1525 Budapest, Hungary; Str. 1, 85741 Garching, Germany; S. Ettori, INAF, Osservatorio Astronomico di Bologna, Via Piero Gob- R. Ciolfi, INAF, Osservatorio Astronomico di Padova, Vicolo dell’ Os- etti, 93/3, 40129 Bologna, Italy; INFN, Sezione di Bologna, viale Berti servatorio 5, I-35122 Padova, Italy; INFN-TIFPA, Trento Institute for Pichat 6/2, 40127 Bologna, Italy; Fundamental Physics and Applications, via Sommarive 14, I-38123 Y. Evangelista, INAF-IAPS-Roma via Fosso del Cavaliere, 100, 00133, Trento, Italy; Rome, Italy; S. Colafrancesco, School of Physics, University of Witwatersrand, M. Feroci, INAF-IAPS-Roma via Fosso del Cavaliere, 100, 00133, Private Bag 3, Wits-2050, Johannesburg, South Africa; Rome, Italy; M. Colpi, Dipartimento di Fisica G. Occhialini, Universit degli Studi A. Ferrara, Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 di Milano Bicocca, Piazza della Scienza 3, 20126 Milano, Italy; INFN, Pisa, Italy; Kavli IPMU, The University of Tokyo, 5-1-5 Kashiwanoha, Sezione di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Kashiwa 277-8583, Japan; Italy; F. Finelli, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, A. Comastri, INAF, Osservatorio Astronomico di Bologna, Via Piero Italy; Gobetti, 93/3, 40129 Bologna, Italy; M. Fiorini, INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica V. Connaughton, Universities Space Research Association, NSSTC, Milano, Via E. Bassini 15, I-20133 Milano, Italy; 320 Sparkman Drive, Huntsville, AL 35805, USA; F. Frontera, Department of Physics and Earth Sciences, University of B. Cordier, IRFU/Departement´ d’Astrophysique, CEA, Universite´ Paris- Ferrara, Via Saragat 1, I-44122 Ferrara, Italy, and INAF-IASF, Via Go- Saclay, F-91191, Gif-sur-Yvette, France; betti, 101, I-40129 Bologna, Italy; C. Contini, OHB-Italia, Via Gallarate, 150 20151 Milano, ITALY; F. Fuschino, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, 46 Amati et al.

Italy; S. Korpela, University of Helsinki, Department of Physics, P.O.Box J. Fynbo, Dark Cosmology Centre, Niels Bohr Institute, University of 48 FIN-00014 University of Helsinki, Finland; Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark; P. Kumar, Department of Astronomy, University of Texas at Austin, A. Gal-Yam, Department of Particle Physics and Astrophysics, Fac- Austin, TX 78712, USA; ulty of Physics, Weizmann Institute of Science, Rehovot 76100, Israel; I. Kuvvetli, DTU Space - National Space Institute Elektrovej, Build- P. Gandhi, Department of Physics & Astronomy, University of Southamp- ing 327, DK-2800 Kongens Lyngby, Denmark; ton, Highfield, Southampton SO17 1BJ, UK; C. Labanti, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, B. Gendre, University of the Virgin Islands, 2 John Brewer’s Bay, Italy; 00802 St Thomas, US Virgin Islands; Etelman Observatory, Bonne M. Lavagna, Politecnico di Milano, Via La Masa 1, 20156 Milano, Resolution, St Thomas, US Virgin Islands; Italy; G. Ghirlanda, INAF - Osservatorio astronomico di Brera, Via E. Bianchi V. Lebrun, LAM, Laboratoire dAstrophysique de Marseille, 13388 46, Merate (LC), I-23807, Italy; Marseille, France; G. Ghisellini, INAF - Osservatorio astronomico di Brera, Via E. Bianchi E. Le Floch, IRFU/Departement´ d’Astrophysique, CEA, Universite´ 46, Merate (LC), I-23807, Italy; Paris-Saclay, F-91191, Gif-sur-Yvette, France; P. Giommi, Italian Space Agency, ASI, via del Politecnico snc, 00133 T. Li, Department of Engineering Physics and Center for Astrophysics, Roma, Italy; Tsinghua University, Beijing, China; A. Gomboc, Centre for Astrophysics and Cosmology, University of F. Longo, Department of Physics, University of Trieste, via Valerio 2, Nova Gorica, Vipavska 11c, 5270 Ajdov sˇcina,ˇ Slovenia; Trieste, Italy; INFN Trieste, via Valerio 2, Trieste, Italy; D. Gotz¨ , IRFU/Departement´ d’Astrophysique, CEA, Universite´ Paris- F. Lu, Institute of High Energy Physics, Beijing 100049, China; Saclay, F-91191, Gif-sur-Yvette, France; M. Lyutikov, Department of Physics, Purdue University, 525 North- A. Grado, INAF - Capodimonte Astronomical observatory Naples, Via western Avenue, West Lafayette, IN 47907-2036 and Department of Moiariello 16 I-80131, Naples, Italy; Physics and McGill Space Institute, McGill University, 3600; Univer- J. Greiner, Max Planck Institute for Astrophysics, Karl-Schwarzschild- sity Street, Montreal, Quebec H3A 2T8, Canada; Str. 1, 85741 Garching, Germany; A. MacFadyen, Center for Cosmology and Particle Physics, New York C. Guidorzi, Department of Physics and Earth Sciences, University of University, New York, NY, USA; Ferrara, Via Saragat 1, I-44122 Ferrara, Italy; U. Maio, Leibniz Institut for Astrophysics, An der Sternwarte 16, 14482 S. Guiriec, Department of Physics, The George Washington Univer- Potsdam, Germany; INAF-Osservatorio Astronomico di Trieste, via sity, 725 21st Street NW, Washington, DC 20052, USA; NASA God- G. Tiepolo 11, 34131 Trieste, Italy; dard Space Flight Center, Greenbelt, MD 20771, USA; Department of E. Maiorano, INAF-IASF Bologna, via Piero Gobetti 101, I-40129 Astronomy, University of Maryland, College Park, MD 20742, USA; Bologna, Italy; Center for Research and Exploration in Space Science and Technology G. Malaguti, INAF-IASF Bologna, via Piero Gobetti 101, I-40129 (CRESST), Greenbelt, MD 20771, USA; Bologna, Italy; M. Hafizi, Department of Physics, University of Tirana, Tirana, Alba- P. Malcovati, Department of Electrical, Computer, and Biomedical nia; Engineering, University of Pavia, Pavia, Italy; L. Hanlon, Space Science Group, School of Physics, University Col- D. Malesani, Dark Cosmology Centre, Niels Bohr Institute, University lege Dublin, Belfield, Dublin 4, Ireland; of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Den- J. Harms, Universit degli Studi di Urbino Carlo Bo, I-61029 Urbino, mark; Italy; L. Maraschi, INAF - Osservatorio astronomico di Brera, Via E. Bianchi M. Hernanz, Institute of Space Sciences (IEECCSIC), Carrer de Can 46, Merate (LC), I-23807, Italy; Magrans s/n, E-08193 Barcelona, Spain; R. Margutti, Center for Interdisciplinary Exploration and Research in J. Hjorth, Dark Cosmology Centre, Niels Bohr Institute, University of Astrophysics (CIERA) and Department of Physics and Astrophysics, Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark; Northwestern University, Evanston, IL 60208, USA; A. Hornstrup, DTU Space - National Space Institute Elektrovej, Build- M. Marisaldi, INAF-IASF Bologna, via Piero Gobetti 101, I-40129 ing 327, DK-2800 Kongens Lyngby, Denmark; Bologna, Italy; R. Hudec, Czech Technical University, Faculty of Electrical Engineer- A. Martin-Carrillo, Space Science Group, School of Physics, Univer- ing, Prague 16627, Czech Republic; Kazan Federal University, Kazan sity College Dublin, Belfield, Dublin 4, Ireland; 420008, Russian Federations; N. Masetti, INAF-IASF Bologna, via Piero Gobetti, 101, I-40129 Bologna, I. Hutchinson, Department of Physics and Astronomy, University of Italy; Departamento de Ciencias F´ısicas, Universidad Andres´ Bello, Leicester, Leicester LE1 7RH, UK; Fernandez´ Concha 700, Las Condes, Santiago, Chile; G. Israel, INAF-Osservatorio Astronomico di Roma, Via Frascati 33, S. McBreen, School of Physics, University College Dublin, Belfield, I-00040 Monte Porzio Catone, Italy; Stillorgan Road, Dublin 4, Ireland; L. Izzo, Instituto de Astrofisica de Andalucia (IAA-CSIC), Glorieta de A. Melandri, INAF - Osservatorio Astronomico di Brera, via E. Bianchi la Astronomia s/n, 18008 Granada, Spain; 36, I-23807 Merate (LC), Italy; P. Jonker, SRON, Netherlands Institute for Space Research, Sorbon- S. Mereghetti, INAF - IASF Milano, Via E. Bassini 15, 20133 Milano, nelaan 2, NL-3584 CA Utrecht, The Netherlands; Department of As- Italy; trophysics/IMAPP, Radboud University, P.O. Box 9010, NL-6500 GL R. Mignani, INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Nijmegen, The Netherlands; Milano, via E. Bassini 15, 20133, Milano, Italy; Janusz Gil Institute of Y. Kaneko, Faculty of Engineering and Natural Sciences, Sabanc Uni- Astronomy, University of Zielona Gora,´ Lubuska 2, 65-265, Zielona versity, Orhanl Tuzla, Istanbul 34956, Turkey; Gora,´ Poland; N. Kawai, Department of Physics, Tokyo Institute of Technology, 2- M. Modjaz, Center for Cosmology and Particle Physics, Department 12-1 Ookayama, Meguro-ku, Tokyo 152-8551; of Physics, New York University, 726 Broadway office 1044, New L. Kiss, Konkoly Observatory, Research Centre for Astronomy and York, NY 10003, USA ; Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklos´ G. Morgante, INAF-IASF Bologna, via Piero Gobetti, 101, I-40129 ut´ 15-17, H-1121 Budapest, Hungary; Bologna, Italy; K. Wiersema, Department of Physics and Astronomy, University of B. Morelli, OHB-Italia, Via Gallarate, 150 20151 Milano, ITALY; Leicester, Leicester LE1 7RH, UK ; D. Morris, Etelman Observatory, St. Thomas, United States Virgin Is- THESEUS 47 lands 00802, USA; College of Science and Math, University of Virgin E. Renotte, Centre Spatial de Liege,` Parc Scientifique du Sart Tilman Islands, St. Thomas, United States Virgin Islands 00802, USA; Avenue du Pre-Aily,` 4031 Angleur-Liege,` Belgium; C. Mundell, Department of Physics, University of Bath, Claverton L. Rezzolla, Institut fur¨ Theoretische Physik, Johann Wolfgang Goethe- Down, Bath BA2 7AY, UK; Universitat,¨ Max-von-Laue-Straße 1, 60438 Frankfurt, Germany; Frank- H. U. Nargaard-Nielsen, DTU Space - National Space Institute Elek- furt Institute for Advanced Studies, Ruth-Moufang-Straße 1, 60438 trovej, Building 327, DK-2800 Kongens Lyngby, Denmark; Frankfurt, Germany; S. Nagataki, Astrophysical Big Bang Laboratory (ABBL), RIKEN, J. Rhoads, School of Earth and Space Exploration, Arizona State Uni- Saitama 351-0198, Japan; versity, Tempe, AZ 85287, USA; Astrophysics Science Division, God- L. Nicastro, INAF - Instituto di Astrofisica Spaziale e Fisica Cosmica, dard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, Via Piero Gobetti 101, I-40129 Bologna, Italy; USA; P. O’Brien, Department of Physics and Astronomy, University of Le- T. Rodic, SPACE-SI, Slovenian Centre of Excellence for Space Sci- icester, Leicester LE1 7RH, UK; ences and Technologies, Ljubljana, Slovenia; N. Omodei, W. W. Hansen Experimental Physics Laboratory, Kavli In- P. Romano, INAF-Osservatorio Astronomico di Brera, via E. Bianchi, stitute for Particle Astrophysics and Cosmology, Department of Physics 46. I-23807 Merate, Italy; and SLAC National Accelerator Laboratory, Stanford University, Stan- P. Rosati, Universita degli Studi di Ferrara, Via Saragat 1, Ferrara, ford, CA 94305, USA; Italy; M. Orlandini, INAF-IASF Bologna, via Piero Gobetti, 101, I-40129 A. Rossi, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, Bologna, Italy; Italy; P. Orleanski, Space Research Center of the Polish Academy of Sci- R. Ruffini, ICRANet, P.zza della Repubblica 10, 65122 Pescara, Italy; ences, Warsaw, Poland; ICRA and Dipartimento di Fisica, Sapienza Universita` di Roma, P.le J. P. Osborne, Department of Physics and Astronomy, University of Aldo Moro 5, 00185 Rome, Italy; Leicester, Leicester LE1 7RH, UK; F. Ryde, The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, A. Paizis, INAF - IASF Milano, Via E. Bassini 15, 20133 Milano, SE-106 91 Stockholm, Sweden; Department of Physics, KTH Royal Italy; Institute of Technology, AlbaNova University Center, SE-106 91 Stock- E. Palazzi, INAF-IASF Bologna, via Piero Gobetti, 101, I-40129 Bologna, holm, Sweden; Italy; L. Sabau-Graziati, Division de Ciencias del Espacio (INTA), Torre- S. Paltani, Department of Astronomy, University of Geneva, ch. d’Ecogia´ jon de Ardoz, Madrid, Spain; 16, CH-1290 Versoix, Switzerland; R. Salvaterra, INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica F. Panessa, INAF-IAPS-Roma via Fosso del Cavaliere, 100, 00133, Milano, via E. Bassini 15, 20133, Milano, Italy ; Rome, Italy; A. Santangelo, Institut fur¨ Astronomie und Astrophysik, Abteilung G. Pareschi, INAF - Osservatorio astronomico di Brera, Via E. Bianchi Hochenergieastrophysik, Kepler Center for Astro and Particle Physics, 46, Merate (LC), I-23807, Italy; Eberhard Karls Universitat,¨ Sand 1, D 72076 Tubingen,¨ Germany; P. Pata´ , Department of Radioelectronics, Faculty of Electrical Engi- S. Savaglio, Physics Dept., University of Calabria, via P. Bucci, 87036, neering, Czech Technical University in Prague, Technicka´ 2, 166 27 Arcavacata di Rende, Italy; Prague 6, Czech Republic; V.Sguera, INAF-IASF Bologna, via P. Gobetti, 101. I-40129 Bologna, A. Pe’er, Department of Physics, University College Cork, Ireland; Italy; A. V. Penacchioni, ICRA Net, Piazza della Repubblica 10, I-65122 P. Schady, Max Planck Institute for extraterrestrial Physics, Giessen- Pescara, Italy; ASI Science Data Center, Via del Politecnico s.n.c., I- bachstrasse 1, 85748 Garching, Germany; 00133 Rome, Italy; Department of Physical Sciences, Earth and Envi- M. Sims, Department of Physics and Astronomy, University of Leices- ronment, University of Siena, Via Roma 56, I-53100 Siena, Italy; ter, Leicester LE1 7RH, UK; V. Petrosian, W. W. Hansen Experimental Physics Laboratory, Kavli W. Skidmore, Warren Skidmore, Thirty Meter Telescope International Institute for Particle Astrophysics and Cosmology, Department of Physics Observatory, 100 W. Walnut St., Suite 300, Pasadena, CA 91124, USA; and SLAC National Accelerator Laboratory, Stanford University, Stan- L. Song, Key Laboratory of Particle Astrophysics, Institute of High ford, CA 94305, USA; Energy Physics, Chinese Academy of Sciences, Beijing 100049, China; E. Pian, Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 J. Soomin, Instituto de Astrofisica de Andalucia (IAA-CSIC), Glorieta Pisa, Italy; de la Astronomia s/n, 18008 Granada, Spain; E. Piedipalumbo, Dipartimento di Fisica, Universita´ degli Studi di E. Stanway, Department of Physics, University of Warwick, Gibbet Napoli Federico II, Compl. Univ. Monte S. Angelo, 80126 Naples, Hill Road, Coventry, CV4 7AL, UK; Italy; INFN, Sez. di Napoli, Compl. Univ. Monte S. Angelo, Edificio R. Starling, University of Leicester, Department of Physics and As- 6, via Cinthia, 80126 Napoli, Italy; tronomy and Leicester Institute of Space and Earth Observation, Uni- T. Piran, Racah Institute of Physics, The Hebrew University of Jerusalem, versity Road, Leicester LE1 7RH, UK; Jerusalem 91904, Israel; G. Stratta, Universita´ degli Studi di Urbino Carlo Bo, I-61029 Urbino, P. Piranomonte, INAF-Osservatorio Astronomico di Roma, Via Fras- Italy; cati 33, I-00040 Monte Porzio Catone, Italy; D. Szecsi´ , Astronomical Institute of the Czech Academy of Sciences, L. Piro, INAF-IAPS-Roma via Fosso del Cavaliere, 100, 00133, Rome, Fricovaˇ 298, 25165 Ondrejov,ˇ Czech Republic; School of Physics and Italy; Astronomy and Institute of Gravitational Wave Astronomy, University A. Rachevski, INFN - Sezione di Trieste, via Valerio 2, I-34127 Tri- of Birmingham, Edgbaston, Birmingham B15 2TT, UK; este, Italy; G. Tagliaferri, INAF - Osservatorio astronomico di Brera, Via E. Bianchi G. Rauw, Universite´ de Liege,` Quartier Agora, Allee´ du 6 Aoutˆ 19c, 46, Merate (LC), I-23807, Italy; B-4000 Sart Tilman, Liege,` Belgium; N. Tanvir, University of Leicester, Department of Physics and Astron- M. Razzano, Department of Physics, University of Pisa and INFN- omy and Leicester Institute of Space & Earth Observation, University Pisa,Pisa, I-56127; Road, Leicester, LE1 7RH, UK; A. Read, Department of Physics and Astronomy, University of Leices- C. Tenzer, Institut fur¨ Astronomie und Astrophysik, Abteilung Hoch- ter, Leicester LE1 7RH, UK; energieastrophysik, Kepler Center for Astro and Particle Physics, Eber- V.Reglero, Image Processing Laboratory, University of Valencia C/Catedraticohard Karls Universitat,¨ Sand 1, D 72076 Tubingen,¨ Germany Jose Beltran, 2, 46980 Paterna (Valencia), Spain; M. Topinka, Dublin Institute for Advanced Studies, School of Cosmic 48 Amati et al.

Physics, 31 Fitzwilliam Place, Dublin 2, Ireland; berg, et al., An absence of neutrinos associated with cosmic-ray E. Troja, Department of Astronomy, University of Maryland, College acceleration in gamma-ray bursts. Nature 484, 351–354 (2012). Park, Maryland 20742-4111, USA; NASA Goddard Space Flight Cen- doi:10.1038/nature11068 ter, 8800 Greenbelt Rd, Greenbelt, Maryland 20771, USA; B.P. Abbott, R. Abbott, T.D. Abbott, M.R. Abernathy, F. Acernese, K. Y. Urata, Institute of Astronomy, National Central University, Chung- Ackley, C. Adams, T. Adams, P. Addesso, R.X. Adhikari, et al., Li 32054, Taiwan GW151226: Observation of Gravitational Waves from a 22-Solar- M. Uslenghi, INAF-IASF, via E. Bassini 15, 20133 Milano, Italy; Mass Binary Black Hole Coalescence. Physical Review Letters A. Vacchi, INFN Trieste, via Valerio 2, Trieste, Italy; 116(24), 241103 (2016a). doi:10.1103/PhysRevLett.116.241103 L. Valenziano, INAF/IASF Bologna, via Gobetti 101, Bologna, Italy; B.P. Abbott, R. Abbott, T.D. Abbott, M.R. Abernathy, F. Acer- M. van Putten, Sejong University, 98 Gunja-Dong Gwangin-gu, Seoul nese, K. Ackley, C. Adams, T. Adams, P. Addesso, R.X. Ad- 143-747, Korea; hikari, et al., Properties of the Binary Black Hole Merger E. Vanzella, INAF Osservatorio Astronomico di Bologna, via Ranzani GW150914. Physical Review Letters 116(24), 241102 (2016b). 1, 40127 Bologna, Italy; doi:10.1103/PhysRevLett.116.241102 S. Vercellone, INAF-Osservatorio Astronomico di Brera, via E. Bianchi, M. Ahangarianabhari, D. Macera, G. Bertuccio, P. Malcovati, M. 46. I-23807 Merate, Italy; Grassi, VEGA: A low-power front-end ASIC for large area multi- S. Vergani, GEPI, Observatoire de Paris, PSL Research University, linear X-ray silicon drift detectors: Design and experimental char- CNRS, Place Jules Janssen, 92190 Meudon, France; INAF/Osservatorio acterization. Nuclear Instruments and Methods in Physics Re- Astronomico di Brera, via Bianchi 46, 23807 Merate (LC), Italy; search A 770, 155–163 (2015). doi:10.1016/j.nima.2014.10.009 G. Vianello, SLAC National Accelerator Laboratory, Stanford Univer- L. Amati, M. Della Valle, Measuring Cosmological Parameters with sity, Stanford, CA 94305, USA; Gamma Ray Bursts. International Journal of Modern Physics D S. Vinciguerra, Institute of Gravitational Wave Astronomy & School 22, 1330028 (2013a). doi:10.1142/S0218271813300280 of Physics and Astronomy, University of Birmingham, Birmingham, L. Amati, M. Della Valle, Measuring Cosmological Parameters with B15 2TT, United Kingdom; Gamma Ray Bursts. International Journal of Modern Physics D D. Watson, Dark Cosmology Centre, Niels Bohr Institute, University 22, 1330028 (2013b). doi:10.1142/S0218271813300280 of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Den- L. Amati, F. Frontera, M. Vietri, J.J.M. in’t Zand, P. Soffitta, E. Costa, mark; S. Del Sordo, E. Pian, L. Piro, L.A. Antonelli, D.D. Fiume, M. R. Willingale, Department of Physics and Astronomy, University of Feroci, G. Gandolfi, C. Guidorzi, J. Heise, E. Kuulkers, N. Masetti, Leicester, Leicester LE1 7RH, UK E. Montanari, L. Nicastro, M. Orlandini, E. Palazzi, Discovery of a C. Wilson-Hodge, NASA/Marshall Space Flight Center, Huntsville, Transient Absorption Edge in the X-ray Spectrum of GRB 990705. AL, USA; Science 290, 953–955 (2000). doi:10.1126/science.290.5493.953 S. Vojtech, Astronomical Institute Academy of Sciences of the Czech L. Amati, F. Frontera, M. Tavani, J.J.M. in’t Zand, A. Antonelli, E. Republic, Fricova 1, Ondrejov, CZ-25165, Czech Republic; Costa, M. Feroci, C. Guidorzi, J. Heise, N. Masetti, E. Mon- D. Yonetoku, Faculty of Mathematics and Physics, Kanazawa Univer- tanari, L. Nicastro, E. Palazzi, E. Pian, L. Piro, P. Soffitta, In- sity, Ishikawa 920-1192, Japan; trinsic spectra and energetics of BeppoSAX Gamma-Ray Bursts G. Zampa, INFN Trieste, via Valerio 2, Trieste, Italy; with known redshifts. A&A 390, 81–89 (2002). doi:10.1051/0004- N. Zampa, INFN Trieste, via Valerio 2, Trieste, Italy; 6361:20020722 B. Zhang, Department of Physics and Astronomy, University of Nevada, L. Amati, F. Frontera, J.J.M. in’t Zand, M. Capalbi, R. Landi, P. Sof- Las Vegas, NV 89154, USA; fitta, L. Vetere, L.A. Antonelli, E. Costa, S. Del Sordo, M. Fe- B. B. Zhang, IAA-CSIC, P.O. Box 03004, E-18080, Granada, Spain; roci, C. Guidorzi, J. Heise, N. Masetti, E. Montanari, L. Nicastro, S. Zhang, Institute of High Energy Physics, Beijing 100049, China; E. Palazzi, L. Piro, Prompt and afterglow X-ray emission from S.-N. Zhang, Institute of High Energy Physics, Beijing 100049, China; the X-Ray Flash of 2002 April 27. A&A 426, 415–423 (2004). J. Zicha, Department of Instrumentation and Control Engineering, Fac- doi:10.1051/0004-6361:20047146 ulty of Mechanical Engineering, Czech Technical University in Prague, L. Amati, C. Guidorzi, F. Frontera, M. Della Valle, F. Finelli, R. Landi, Technicka 4, 166 07 Praha 6, Czech Republic E. Montanari, Measuring the cosmological parameters with the Ep,i-Eiso correlation of gamma-ray bursts. MNRAS 391, 577–584 (2008). doi:10.1111/j.1365-2966.2008.13943.x References J.R.P. Angel, Lobster eyes as X-ray telescopes. ApJ 233, 364–373 (1979). doi:10.1086/157397 M.J. Aschwanden, D. Tsiklauri, The Hydrodynamic Evolution of J. Abadie, B.P. Abbott, R. Abbott, T. Accadia, F. Acernese, R. Ad- Impulsively Heated Coronal Loops: Explicit Analytical Ap- hikari, P. Ajith, B. Allen, G. Allen, E. Amador Ceron, et al., proximations. ApJS 185, 171–185 (2009). doi:10.1088/0067- All-sky search for gravitational-wave bursts in the first joint 0049/185/1/171 81 LIGO-GEO-Virgo run. Phys. Rev. D (10), 102001 (2010a). H. Atek, J. Richard, M. Jauzac, J.-P. Kneib, P. Natarajan, M. Limousin, doi:10.1103/PhysRevD.81.102001 D. Schaerer, E. Jullo, H. Ebeling, E. Egami, B. Clement, Are J. Abadie, B.P. Abbott, R. Abbott, M. Abernathy, C. Adams, R. Ad- Ultra-faint Galaxies at z = 6-8 Responsible for Cosmic Reion- hikari, P. Ajith, B. Allen, G. Allen, E. Amador Ceron, et al., ization? Combined Constraints from the Hubble Frontier Fields First Search for Gravitational Waves from the Youngest Known Clusters and Parallels. ApJ 814, 69 (2015) 722 Neutron Star. ApJ , 1504–1513 (2010b). doi:10.1088/0004- L. Baiotti, L. Rezzolla, Binary neutron star mergers: a review of Ein- 637X/722/2/1504 stein richest laboratory. Reports on Progress in Physics 80(9), J. Abadie, B.P. Abbott, R. Abbott, M. Abernathy, T. Accadia, F. Ac- 096901 (2017). doi:10.1088/1361-6633/aa67bb ernese, C. Adams, R. Adhikari, P. Ajith, B. Allen, et al., TOPI- D.L. Band, Comparison of the Gamma-Ray Burst Sensitivity of Dif- CAL REVIEW: Predictions for the rates of compact binary coa- ferent Detectors. ApJ 588, 945–951 (2003). doi:10.1086/374242 lescences observable by ground-based gravitational-wave detec- R. Basak, A.R. Rao, Pulse-wise Amati correlation in Fermi 27 tors. Classical and Quantum Gravity (17), 173001 (2010c). gamma-ray bursts. MNRAS 436, 3082–3088 (2013). doi:10.1088/0264-9381/27/17/173001 doi:10.1093/mnras/stt1790 R. Abbasi, Y. Abdou, T. Abu-Zayyad, M. Ackermann, J. Adams, R. Basak, A.R. Rao, Thermal Emissions Spanning the Prompt and the J.A. Aguilar, M. Ahlers, D. Altmann, K. Andeen, J. Auffen- THESEUS 49

Afterglow Phases of the Ultra-long GRB 130925A. ApJ 807, 34 Picolli, Imaging performance of a large-area Silicon Drift Detector (2015). doi:10.1088/0004-637X/807/1/34 for X-ray astronomy. Nuclear Instruments and Methods in Physics D.S. Baskill, P.J. Wheatley, J.P. Osborne, The complete set Research A 633, 22–30 (2011). doi:10.1016/j.nima.2010.12.237 of ASCA X-ray observations of non-magnetic cataclysmic R. Campana, Y. Evangelista, F. Fuschino, D. Ahangarianabhari variables. MNRAS 357, 626–644 (2005). doi:10.1111/j.1365- M. Macera, G. Bertuccio, M. Grassi, C. Labanti, M. Marisaldi, 2966.2005.08677.x P. Malcovati, A. Rachevski, G. Zampa, N. Zampa, L. Andreani, A. Bauswein, H.-T. Janka, Measuring Neutron-Star Proper- G. Baldazzi, E. Del Monte, Y. Favre, M. Feroci, F. Muleri, I. Ra- ties via Gravitational Waves from Neutron-Star Merg- shevskaya, A. Vacchi, F. Ficorella, G. Giacomini, A. Picciotto, M. ers. Physical Review Letters 108(1), 011101 (2012). Zuffa, Characterization of the VEGA ASIC coupled to large area doi:10.1103/PhysRevLett.108.011101 position-sensitive Silicon Drift Detectors. Journal of Instrumenta- A.O. Benz, M. Gudel,¨ Physical Processes in Magnetically Driven tion 9, 08008 (2014). doi:10.1088/1748-0221/9/08/P08008 Flares on the Sun, Stars, and Young Stellar Objects. ARA&A 48, S. Campana, V. Mangano, A.J. Blustin, P. Brown, D.N. Burrows, G. 241–287 (2010). doi:10.1146/annurev-astro-082708-101757 Chincarini, J.R. Cummings, G. Cusumano, M. Della Valle, D. E. Berger, Short-Duration Gamma-Ray Bursts. ARA&A 52, 43–105 Malesani, P. Mesz´ aros,´ J.A. Nousek, M. Page, T. Sakamoto, E. (2014). doi:10.1146/annurev-astro-081913-035926 Waxman, B. Zhang, Z.G. Dai, N. Gehrels, S. Immler, F.E. Mar- J.S. Bloom, D.E. Holz, S.A. Hughes, K. Menou, A. Adams, S.F. An- shall, K.O. Mason, A. Moretti, P.T. O’Brien, J.P. Osborne, K.L. derson, A. Becker, G.C. Bower, N. Brandt, B. Cobb, K. Cook, A. Page, P. Romano, P.W.A. Roming, G. Tagliaferri, L.R. Comin- Corsi, S. Covino, D. Fox, A. Fruchter, C. Fryer, J. Grindlay, D. sky, P. Giommi, O. Godet, J.A. Kennea, H. Krimm, L. An- Hartmann, Z. Haiman, B. Kocsis, L. Jones, A. Loeb, S. Marka, gelini, S.D. Barthelmy, P.T. Boyd, D.M. Palmer, A.A. Wells, N.E. B. Metzger, E. Nakar, S. Nissanke, D.A. Perley, T. Piran, D. Poz- White, The association of GRB 060218 with a supernova and nanski, T. Prince, J. Schnittman, A. Soderberg, M. Strauss, P.S. the evolution of the shock wave. Nature 442, 1008–1010 (2006). Shawhan, D.H. Shoemaker, J. Sievers, C. Stubbs, G. Tagliaferri, P. doi:10.1038/nature04892 Ubertini, P. Wozniak, Astro2010 Decadal Survey Whitepaper: Co- V.F. Cardone, M.G. Dainotti, S. Capozziello, R. Willingale, Con- ordinated Science in the Gravitational and Electromagnetic Skies. straining cosmological parameters by gamma-ray burst X- ArXiv e-prints (2009) ray afterglow light curves. MNRAS 408, 1181–1186 (2010). J.S. Bloom, D. Giannios, B.D. Metzger, S.B. Cenko, D.A. Per- doi:10.1111/j.1365-2966.2010.17197.x ley, N.R. Butler, N.R. Tanvir, A.J. Levan, P.T. O’Brien, L.E. J. Caruana, A.J. Bunker, S.M. Wilkins, E.R. Stanway, M. Lacy, M.J. Strubbe, F. De Colle, E. Ramirez-Ruiz, W.H. Lee, S. Nayak- Jarvis, S. Lorenzoni, S. Hickey, No evidence for Lyman-alpha shin, E. Quataert, A.R. King, A. Cucchiara, J. Guillochon, G.C. emission in spectroscopy of z 7 candidate galaxies. MNRAS 427, Bower, A.S. Fruchter, A.N. Morgan, A.J. van der Horst, A Pos- 3055–3070 (2012). doi:10.1111/j.1365-2966.2012.21996.x sible Relativistic Jetted Outburst from a Massive Black Hole J. Caruana, A.J. Bunker, S.M. Wilkins, E.R. Stanway, S. Lorenzoni, Fed by a Tidally Disrupted Star. Science 333, 203 (2011). M.J. Jarvis, H. Ebert, Spectroscopy of z 7 candidate galaxies: doi:10.1126/science.1207150 using Lyman-alpha to constrain the neutral fraction of hydrogen E. Bozzo, M. Falanga, L. Stella, Are There Magnetars in High-Mass in the high-redshift universe. MNRAS 443, 2831–2842 (2014). X-Ray Binaries? The Case of Supergiant Fast X-Ray Transients. doi:10.1093/mnras/stu1341 ApJ 683, 1031–1044 (2008). doi:10.1086/589990 E. Chassande-Mottin, LIGO Scientific Collaboration, Virgo Collabora- E. Bozzo, V. Bhalerao, P. Pradhan, J. Tomsick, P. Romano, C. Ferrigno, tion, Joint searches for gravitational waves and high-energy neu- S. Chaty, L. Oskinova, A. Manousakis, R. Walter, M. Falanga, S. trinos, in Journal of Physics Conference Series. Journal of Physics Campana, L. Stella, M. Ramolla, R. Chini, Multi-wavelength ob- Conference Series, vol. 243, 2010, p. 012002. doi:10.1088/1742- servations of IGR J17544-2619 from quiescence to outburst. A&A 6596/243/1/012002 596, 16 (2016). doi:10.1051/0004-6361/201629311 E. Chassande-Mottin, M. Hendry, P.J. Sutton, S. Marka,´ Multimessen- E.F. Brown, Superburst Ignition and Implications for Neutron Star In- ger astronomy with the Einstein Telescope. General Relativity and teriors. ApJ 614, 57–60 (2004). doi:10.1086/425562 Gravitation 43, 437–464 (2011). doi:10.1007/s10714-010-1019-z N. Bucciantini, B.D. Metzger, T.A. Thompson, E. Quataert, Short C.C. Cheung, P. Jean, S.N. Shore, Ł. Stawarz, R.H.D. Corbet, J. gamma-ray bursts with extended emission from magnetar birth: Knodlseder,¨ S. Starrfield, D.L. Wood, R. Desiante, F. Longo, G. jet formation and collimation. MNRAS 419, 1537–1545 (2012). Pivato, K.S. Wood, Fermi-LAT Gamma-Ray Detections of Classi- doi:10.1111/j.1365-2966.2011.19810.x cal Novae V1369 Centauri 2013 and V5668 Sagittarii 2015. ApJ D.N. Burrows, J.A. Kennea, G. Ghisellini, V. Mangano, B. Zhang, 826, 142 (2016). doi:10.3847/0004-637X/826/2/142 K.L. Page, M. Eracleous, P. Romano, T. Sakamoto, A.D. Falcone, R. Ciolfi, X-ray Flashes Powered by the Spindown of Long-lived Neu- J.P. Osborne, S. Campana, A.P. Beardmore, A.A. Breeveld, M.M. tron Stars. ApJ 829, 72 (2016). doi:10.3847/0004-637X/829/2/72 Chester, R. Corbet, S. Covino, J.R. Cummings, P. D’Avanzo, V. R. Ciolfi, L. Rezzolla, Poloidal-field Instability in Magnetized Rela- D’Elia, P. Esposito, P.A. Evans, D. Fugazza, J.M. Gelbord, K. Hi- tivistic Stars. ApJ 760, 1 (2012). doi:10.1088/0004-637X/760/1/1 roi, S.T. Holland, K.Y. Huang, M. Im, G. Israel, Y. Jeon, Y.-B. R. Ciolfi, D.M. Siegel, Short gamma-ray bursts from binary neutron Jeon, H.D. Jun, N. Kawai, J.H. Kim, H.A. Krimm, F.E. Marshall, star mergers: the time-reversal scenario. ArXiv e-prints (2015a) P. Mesz´ aros,´ H. Negoro, N. Omodei, W.-K. Park, J.S. Perkins, R. Ciolfi, D.M. Siegel, Short Gamma-Ray Bursts in the “Time- M. Sugizaki, H.-I. Sung, G. Tagliaferri, E. Troja, Y. Ueda, Y. reversal” Scenario. ApJ 798, 36 (2015b). doi:10.1088/2041- Urata, R. Usui, L.A. Antonelli, S.D. Barthelmy, G. Cusumano, P. 8205/798/2/L36 Giommi, A. Melandri, M. Perri, J.L. Racusin, B. Sbarufatti, M.H. R. Ciolfi, S.K. Lander, G.M. Manca, L. Rezzolla, Instability-driven Siegel, N. Gehrels, Relativistic jet activity from the tidal disrup- Evolution of Poloidal Magnetic Fields in Relativistic Stars. ApJ tion of a star by a massive black hole. Nature 476, 421–424 (2011). 736, 6 (2011). doi:10.1088/2041-8205/736/1/L6 doi:10.1038/nature10374 A. Corsi, B.J. Owen, Maximum gravitational-wave energy emissi- R. Campana, G. Zampa, M. Feroci, A. Vacchi, V. Bonvicini, E. Del ble in magnetar flares. Phys. Rev. D 83(10), 104014 (2011). Monte, Y. Evangelista, F. Fuschino, C. Labanti, M. Marisaldi, F. doi:10.1103/PhysRevD.83.104014 Muleri, L. Pacciani, M. Rapisarda, A. Rashevsky, A. Rubini, P. A. Cumming, J. Macbeth, The Thermal Evolution following a Su- Soffitta, N. Zampa, G. Baldazzi, E. Costa, I. Donnarumma, M. perburst on an Accreting Neutron Star. ApJ 603, 37–40 (2004). Grassi, F. Lazzarotto, P. Malcovati, M. Mastropietro, E. Morelli, L. doi:10.1086/382873 50 Amati et al.

C. Cutler, K.S. Thorne, An Overview of Gravitational-Wave Sources. N. Scoville, J. Strader, E. Tremou, R. Salinas, R. Chavez,´ Highest ArXiv General Relativity and Quantum Cosmology e-prints Redshift Image of Neutral Hydrogen in Emission: A CHILES De- (2002) tection of a Starbursting Galaxy at z = 0.376. ApJ 824, 1 (2016). M.G. Dainotti, V.F. Cardone, S. Capozziello, A time-luminosity corre- doi:10.3847/2041-8205/824/1/L1 lation for γ-ray bursts in the X-rays. MNRAS 391, 79–83 (2008). D. Fertig, K. Mukai, T. Nelson, J.K. Cannizzo, The Fall and the doi:10.1111/j.1745-3933.2008.00560.x Rise of X-Rays from Dwarf Novae in Outburst: RXTE Obser- M.G. Dainotti, V. Petrosian, J. Singal, M. Ostrowski, Determina- vations of VW Hydri and WW Ceti. PASP 123, 1054 (2011). tion of the Intrinsic Luminosity Time Correlation in the X- doi:10.1086/661949 Ray Afterglows of Gamma-Ray Bursts. ApJ 774, 157 (2013a). W. Fong, E. Berger, R. Chornock, R. Margutti, A.J. Levan, N.R. Tanvir, doi:10.1088/0004-637X/774/2/157 R.L. Tunnicliffe, I. Czekala, D.B. Fox, D.A. Perley, S.B. Cenko, M.G. Dainotti, V.F. Cardone, E. Piedipalumbo, S. Capozziello, Slope B.A. Zauderer, T. Laskar, S.E. Persson, A.J. Monson, D.D. Kel- evolution of GRB correlations and cosmology. MNRAS 436, 82– son, C. Birk, D. Murphy, M. Servillat, G. Anglada, Demographics 88 (2013b). doi:10.1093/mnras/stt1516 of the Galaxies Hosting Short-duration Gamma-Ray Bursts. ApJ M.G. Dainotti, R. Del Vecchio, N. Shigehiro, S. Capozziello, Selection 769, 56 (2013). doi:10.1088/0004-637X/769/1/56 Effects in Gamma-Ray Burst Correlations: Consequences on the M. Friis, A. De Cia, T. Kruhler,¨ J.P.U. Fynbo, C. Ledoux, P.M. Ratio between Gamma-Ray Burst and Star Formation Rates. ApJ Vreeswijk, D.J. Watson, D. Malesani, J. Gorosabel, R.L.C. Star- 800, 31 (2015). doi:10.1088/0004-637X/800/1/31 ling, P. Jakobsson, K. Varela, K. Wiersema, A.P. Drachmann, A. M.G. Dainotti, S. Postnikov, X. Hernandez, M. Ostrowski, A Funda- Trotter, C.C. Thone,¨ A. de Ugarte Postigo, V. D’Elia, J. Elliott, mental Plane for Long Gamma-Ray Bursts with X-Ray Plateaus. M. Maturi, P. Goldoni, J. FriisGreiner, J. Haislip, L. Kaper, F. ApJ 825, 20 (2016). doi:10.3847/2041-8205/825/2/L20 Knust, A. LaCluyze, B. Milvang-Jensen, D. Reichart, S. Schulze, M. Dainotti, V. Petrosian, R. Willingale, P. O’Brien, M. Ostrowski, V. Sudilovsky, N. Tanvir, S.D. Vergani, The warm, the excited, and S. Nagataki, Luminosity-time and luminosity-luminosity correla- the molecular gas: GRB 121024A shining through its star-forming tions for GRB prompt and afterglow plateau emissions. MNRAS galaxy. MNRAS 451, 167–183 (2015). doi:10.1093/mnras/stv960 451, 3898–3908 (2015). doi:10.1093/mnras/stv1229 C.L. Fryer, D.E. Holz, S.A. Hughes, Gravitational Wave Emission N. Dalal, D.E. Holz, S.A. Hughes, B. Jain, Short GRB and binary black from Core Collapse of Massive Stars. ApJ 565, 430–446 (2002). hole standard sirens as a probe of dark energy. Phys. Rev. D 74(6), doi:10.1086/324034 063006 (2006). doi:10.1103/PhysRevD.74.063006 F. Fuschino, C. Labanti, M. Galli, M. Marisaldi, A. Bulgarelli, F. Gi- S. Dall’Osso, G. Stratta, D. Guetta, S. Covino, G. De Cesare, L. Stella, anotti, M. Trifoglio, A. Argan, E. Del Monte, I. Donnarumma, Gamma-ray bursts afterglows with energy injection from a spin- M. Feroci, F. Lazzarotto, L. Pacciani, M. Tavani, A. Trois, ning down neutron star. A&A 526, 121 (2011). doi:10.1051/0004- Search of GRB with AGILE Minicalorimeter. Nuclear Instru- 6361/201014168 ments and Methods in Physics Research A 588, 17–21 (2008). M.B. Davies, A. King, S. Rosswog, G. Wynn, Gamma-Ray Bursts, doi:10.1016/j.nima.2008.01.004 Supernova Kicks, and Gravitational Radiation. ApJ 579, 63–66 J.P.U. Fynbo, P. Jakobsson, J.X. Prochaska, D. Malesani, C. Ledoux, (2002). doi:10.1086/345288 A. de Ugarte Postigo, M. Nardini, P.M. Vreeswijk, K. Wiersema, M. Demianski, E. Piedipalumbo, D. Sawant, L. Amati, Cosmol- J. Hjorth, J. Sollerman, H.-W. Chen, C.C. Thone,¨ G. Bjornsson,¨ ogy with gamma-ray bursts. I. The Hubble diagram through J.S. Bloom, A.J. Castro-Tirado, L. Christensen, A. De Cia, A.S. the calibrated Ep,i-Eiso correlation. A&A 598, 112 (2017). Fruchter, J. Gorosabel, J.F. Graham, A.O. Jaunsen, B.L. Jensen, doi:10.1051/0004-6361/201628909 D.A. Kann, C. Kouveliotou, A.J. Levan, J. Maund, N. Masetti, Y. Evangelista, M. Feroci, E. Costa, E. Del Monte, I. Donnarumma, I. B. Milvang-Jensen, E. Palazzi, D.A. Perley, E. Pian, E. Rol, P. Lapshov, F. Lazzarotto, L. Pacciani, M. Rapisarda, P. Soffitta, A. Schady, R.L.C. Starling, N.R. Tanvir, D.J. Watson, D. Xu, T. Au- Argan, G. Barbiellini, F. Boffelli, A. Bulgarelli, P. Caraveo, P.W. gusteijn, F. Grundahl, J. Telting, P.-O. Quirion, Low-resolution Cattaneo, A. Chen, F. D’Ammando, G. Di Cocco, F. Fuschino, M. Spectroscopy of Gamma-ray Burst Optical Afterglows: Biases in Galli, F. Gianotti, A. Giuliani, C. Labanti, P. Lipari, F. Longo, M. the Swift Sample and Characterization of the Absorbers. ApJS Marisaldi, S. Mereghetti, E. Moretti, A. Morselli, A. Pellizzoni, 185, 526–573 (2009). doi:10.1088/0067-0049/185/2/526 F. Perotti, G. Piano, P. Picozza, M. Pilia, M. Prest, G. Pucella, A. H. Gao, B. Zhang, H.-J. Lu,¨ Constraints on binary neutron star merger Rappoldi, S. Sabatini, E. Striani, M. Tavani, M. Trifoglio, A. Trois, product from short GRB observations. Phys. Rev. D 93(4), 044065 E. Vallazza, S. Vercellone, V. Vittorini, A. Zambra, L.A. Antonelli, (2016). doi:10.1103/PhysRevD.93.044065 S. Cutini, C. Pittori, B. Preger, P. Santolamazza, F. Verrecchia, P. H. Gao, X. Ding, X.-F. Wu, B. Zhang, Z.-G. Dai, Bright Broad- Giommi, L. Salotti, Temporal Properties of GX 301-2 Over a Year- band Afterglows of Gravitational Wave Bursts from Mergers of long Observation with SuperAGILE. ApJ 708, 1663–1673 (2010). Binary Neutron Stars. ApJ 771, 86 (2013). doi:10.1088/0004- doi:10.1088/0004-637X/708/2/1663 637X/771/2/86 R. Farinelli, P. Romano, V. Mangano, C. Ceccobello, L. Ducci, S. E. Gatti, P. Rehak, Semiconductor drift chamber An application of Vercellone, P. Esposito, J.A. Kennea, D.N. Burrows, Swift ob- a novel charge transport scheme. Nuclear Instruments and Meth- servations of two supergiant fast X-ray transient prototypes in ods in Physics Research 225, 608–614 (1984). doi:10.1016/0167- outburst. MNRAS 424, 2854–2863 (2012). doi:10.1111/j.1365- 5087(84)90113-3 2966.2012.21422.x S. Gezari, R. Chornock, A. Rest, M.E. Huber, K. Forster, E. Berger, F. Favata, Large stellar flares: a review of recent novel results, in Stel- P.J. Challis, J.D. Neill, D.C. Martin, T. Heckman, A. Lawrence, lar Coronae in the Chandra and XMM-NEWTON Era, ed. by F. C. Norman, G. Narayan, R.J. Foley, G.H. Marion, D. Scolnic, L. Favata, J.J. Drake Astronomical Society of the Pacific Conference Chomiuk, A. Soderberg, K. Smith, R.P. Kirshner, A.G. Riess, S.J. Series, vol. 277, 2002, p. 115 Smartt, C.W. Stubbs, J.L. Tonry, W.M. Wood-Vasey, W.S. Burgett, X. Fernandez,´ H.B. Gim, J.H. van Gorkom, M.S. Yun, E. Momjian, A. K.C. Chambers, T. Grav, J.N. Heasley, N. Kaiser, R.-P. Kudritzki, Popping, L. Chomiuk, K.M. Hess, L. Hunt, K. Kreckel, D. Lucero, E.A. Magnier, J.S. Morgan, P.A. Price, An ultraviolet-optical flare N. Maddox, T. Oosterloo, D.J. Pisano, M.A.W. Verheijen, C.A. from the tidal disruption of a helium-rich stellar core. Nature 485, Hales, A. Chung, R. Dodson, K. Golap, J. Gross, P. Henning, J. 217–220 (2012). doi:10.1038/nature10990 Hibbard, Y.L. Jaffe,´ J. Donovan Meyer, M. Meyer, M. Sanchez- G. Ghirlanda, G. Ghisellini, D. Lazzati, C. Firmani, Gamma-Ray Barrantes, D. Schiminovich, A. Wicenec, E. Wilcots, M. Bershady, Bursts: New Rulers to Measure the Universe. ApJ 613, 13–16 THESEUS 51

(2004). doi:10.1086/424915 Fishman, S. Foley, M. Gibby, M.M. Giles, J. Greiner, D. Gruber, G. Ghirlanda, Z. Bosnjak, G. Ghisellini, F. Tavecchio, C. Firmani, A. von Kienlin, M. Kippen, C. Kouveliotou, S. McBreen, C.A. Blackbody components in gamma-ray bursts spectra? MNRAS Meegan, W. Paciesas, R. Preece, A. Rau, D. Tierney, A.J. van der 379, 73–85 (2007). doi:10.1111/j.1365-2966.2007.11890.x Horst, C. Wilson-Hodge, Detection of a Thermal Spectral Com- G. Ghirlanda, R. Salvaterra, G. Ghisellini, S. Mereghetti, G. Tagli- ponent in the Prompt Emission of GRB 100724B. ApJ 727, 33 aferri, S. Campana, J.P. Osborne, P. O’Brien, N. Tanvir, D. (2011). doi:10.1088/2041-8205/727/2/L33 Willingale, L. Amati, S. Basa, M.G. Bernardini, D. Burlon, S. O.E. Hartoog, D. Malesani, J.P.U. Fynbo, T. Goto, T. Kruhler,¨ P.M. Covino, P. D’Avanzo, F. Frontera, D. Gotz,¨ A. Melandri, L. Vreeswijk, A. De Cia, D. Xu, P. Møller, S. Covino, V. D’Elia, Nava, L. Piro, S.D. Vergani, Accessing the population of high- H. Flores, P. Goldoni, J. Hjorth, P. Jakobsson, J.-K. Krogager, redshift Gamma Ray Bursts. MNRAS 448, 2514–2524 (2015). L. Kaper, C. Ledoux, A.J. Levan, B. Milvang-Jensen, J. Soller- doi:10.1093/mnras/stv183 man, M. Sparre, G. Tagliaferri, N.R. Tanvir, A. de Ugarte Postigo, G. Ghirlanda, O.S. Salafia, A. Pescalli, G. Ghisellini, R. Salvaterra, E. S.D. Vergani, K. Wiersema, J. Datson, R. Salinas, K. Mikkelsen, Chassande-Mottin, M. Colpi, F. Nappo, P. D’Avanzo, A. Melandri, N. Aghanim, VLT/X-Shooter spectroscopy of the afterglow of the M.G. Bernardini, M. Branchesi, S. Campana, R. Ciolfi, S. Covino, Swift GRB 130606A. Chemical abundances and reionisation at z D. Gotz,¨ S.D. Vergani, M. Zennaro, G. Tagliaferri, Short gamma- ˜ 6. A&A 580, 139 (2015). doi:10.1051/0004-6361/201425001 ray bursts at the dawn of the gravitational wave era. A&A 594, 84 A. Heger, C.L. Fryer, S.E. Woosley, N. Langer, D.H. Hartmann, How (2016). doi:10.1051/0004-6361/201628993 Massive Single Stars End Their Life. ApJ 591, 288–300 (2003). B. Giacomazzo, L. Rezzolla, N. Stergioulas, Collapse of differentially doi:10.1086/375341 rotating neutron stars and cosmic censorship. Phys. Rev. D 84(2), A. Heger, A. Cumming, D.K. Galloway, S.E. Woosley, Models of Type 024022 (2011). doi:10.1103/PhysRevD.84.024022 I X-Ray Bursts from GS 1826-24: A Probe of rp-Process Hydro- J. Gorosabel, J.U. Fynbo, J. Hjorth, C. Wolf, M.I. Andersen, H. Ped- gen Burning. ApJ 671, 141–144 (2007). doi:10.1086/525522 ersen, L. Christensen, B.L. Jensen, P. Moller,¨ J. Afonso, M.A. G. Hinshaw, D. Larson, E. Komatsu, D.N. Spergel, C.L. Bennett, J. Treyer, G. Mallen-Ornelas,´ A.J. Castro-Tirado, A. Fruchter, J. Dunkley, M.R. Nolta, M. Halpern, R.S. Hill, N. Odegard, L. Page, Greiner, E. Pian, P.M. Vreeswijk, F. Frontera, L. Kaper, S. Klose, K.M. Smith, J.L. Weiland, B. Gold, N. Jarosik, A. Kogut, M. C. Kouveliotou, N. Masetti, E. Palazzi, E. Rol, I. Salamanca, Limon, S.S. Meyer, G.S. Tucker, E. Wollack, E.L. Wright, Nine- N. Tanvir, R.A.M.J. Wijers, E. van den Heuvel, Strategies for year Wilkinson Microwave Anisotropy Probe (WMAP) Obser- prompt searches for GRB afterglows: The discovery of the ¡AS- vations: Cosmological Parameter Results. ApJS 208, 19 (2013). TROBJ¿GRB 001011¡/ASTROBJ¿ optical/near-infrared counter- doi:10.1088/0067-0049/208/2/19 part using colour-colour selection. A&A 384, 11–23 (2002). J. Hjorth, D. Malesani, P. Jakobsson, A.O. Jaunsen, J.P.U. Fynbo, J. doi:10.1051/0004-6361:20011598 Gorosabel, T. Kruhler,¨ A.J. Levan, M.J. Michałowski, B. Milvang- A. Grazian, E. Giallongo, D. Paris, K. Boutsia, M. Dickinson, P. San- Jensen, P. Møller, S. Schulze, N.R. Tanvir, D. Watson, The Opti- tini, R.A. Windhorst, R.A. Jansen, S.H. Cohen, T.A. Ashcraft, C. cally Unbiased Gamma-Ray Burst Host (TOUGH) Survey. I. Sur- Scarlata, M.J. Rutkowski, E. Vanzella, F. Cusano, S. Cristiani, vey Design and Catalogs. ApJ 756, 187 (2012). doi:10.1088/0004- M. Giavalisco, H.C. Ferguson, A. Koekemoer, N.A. Grogin, M. 637X/756/2/187 Castellano, F. Fiore, A. Fontana, F. Marchi, F. Pedichini, L. Pen- A.M. Hopkins, J.F. Beacom, On the Normalization of the Cos- tericci, R. Amor´ın, G. Barro, A. Bonchi, A. Bongiorno, S.M. mic Star Formation History. ApJ 651, 142–154 (2006). Faber, M. Fumana, A. Galametz, L. Guaita, D.D. Kocevski, E. doi:10.1086/506610 Merlin, M. Nonino, R.W. O’Connell, S. Pilo, R.E. Ryan, E. Sani, IceCube-Gen2 Collaboration, :, M.G. Aartsen, M. Ackermann, J. R. Speziali, V. Testa, B. Weiner, H. Yan, Lyman continuum es- Adams, J.A. Aguilar, M. Ahlers, M. Ahrens, D. Altmann, T. An- cape fraction of faint galaxies at z 3.3 in the CANDELS/GOODS- derson, et al., IceCube-Gen2: A Vision for the Future of Neutrino North, EGS, and COSMOS fields with LBC. A&A 602, 18 (2017). Astronomy in Antarctica. ArXiv e-prints (2014) doi:10.1051/0004-6361/201730447 L. Izzo, R. Ruffini, A.V. Penacchioni, C.L. Bianco, L. Caito, S.K. J. Greiner, Supersoft X-ray sources. Proceedings., in Supersoft X- Chakrabarti, J.A. Rueda, A. Nandi, B. Patricelli, A double com- Ray Sources, ed. by J. Greiner Lecture Notes in Physics, Berlin ponent in GRB 090618: a proto-black hole and a genuinely Springer Verlag, vol. 472, 1996 long gamma-ray burst. A&A 543, 10 (2012). doi:10.1051/0004- J. Greiner, J.G. Cuby, M.J. McCaughrean, An unusually massive 6361/201117436 stellar black hole in the Galaxy. Nature 414, 522–525 (2001). P. Jakobsson, J. Hjorth, D. Malesani, R. Chapman, J.P.U. Fynbo, N.R. doi:10.1038/35107019 Tanvir, B. Milvang-Jensen, P.M. Vreeswijk, G. Letawe, R.L.C. J. Greiner, T. Kruhler,¨ S. Klose, P. Afonso, C. Clemens, R. Filgas, D.H. Starling, The Optically Unbiased GRB Host (TOUGH) Survey. Hartmann, A. Kupc¨ u¨ Yoldas¸, M. Nardini, F. Olivares E., A. Rau, III. Redshift Distribution. ApJ 752, 62 (2012). doi:10.1088/0004- A. Rossi, P. Schady, A. Updike, The nature of “dark” gamma-ray 637X/752/1/62 bursts. A&A 526, 30 (2011). doi:10.1051/0004-6361/201015458 Z.-P. Jin, X. Li, Z. Cano, S. Covino, Y.-Z. Fan, D.-M. Wei, The J. Greiner, P.A. Mazzali, D.A. Kann, T. Kruhler,¨ E. Pian, S. Pren- Light Curve of the Macronova Associated with the Long-Short tice, F. Olivares E., A. Rossi, S. Klose, S. Taubenberger, F. Knust, Burst GRB 060614. ApJ 811, 22 (2015). doi:10.1088/2041- P.M.J. Afonso, C. Ashall, J. Bolmer, C. Delvaux, R. Diehl, J. El- 8205/811/2/L22 liott, R. Filgas, J.P.U. Fynbo, J.F. Graham, A.N. Guelbenzu, S. P. Jonker, P. O’Brien, L. Amati, J.-L. Atteia, S. Campana, P. Evans, R. Kobayashi, G. Leloudas, S. Savaglio, P. Schady, S. Schmidl, T. Fender, C. Kouveliotou, G. Lodato, J. Osborne, L. Piro, A. Rau, N. Schweyer, V. Sudilovsky, M. Tanga, A.C. Updike, H. van Eerten, Tanvir, R. Willingale, The Hot and Energetic Universe: Luminous K. Varela, A very luminous magnetar-powered supernova associ- extragalactic transients. ArXiv e-prints (2013) ated with an ultra-long γ-ray burst. Nature 523, 189–192 (2015). D.A. Kann, P. Schady, F. Olivares E., S. Klose, A. Rossi, D.A. Perley, doi:10.1038/nature14579 T. Kruhler,¨ J. Greiner, A. Nicuesa Guelbenzu, J. Elliott, F. Knust, M. Gudel,¨ X-ray astronomy of stellar coronae. A&A Rev. 12, 71–237 R. Filgas, E. Pian, P. Mazzali, J.P.U. Fynbo, G. Leloudas, P.M.J. (2004). doi:10.1007/s00159-004-0023-2 Afonso, C. Delvaux, J.F. Graham, A. Rau, S. Schmidl, S. Schulze, S. Guiriec, V. Connaughton, M.S. Briggs, M. Burgess, F. Ryde, F. M. Tanga, A.C. Updike, K. Varela, The Optical/NIR afterglow of Daigne, P. Mesz´ aros,´ A. Goldstein, J. McEnery, N. Omodei, P.N. GRB 111209A: Complex yet not Unprecedented. ArXiv e-prints Bhat, E. Bissaldi, A. Camero-Arranz, V. Chaplin, R. Diehl, G. (2017) 52 Amati et al.

J. Kanner, J. Camp, J. Racusin, N. Gehrels, D. White, Seeking Coun- A.J. van der Horst, G. Leloudas, A.N. Morgan, K. Misra, G.C. terparts to Advanced LIGO/Virgo Transients with Swift. ApJ 759, Bower, J. Farihi, R.L. Tunnicliffe, M. Modjaz, J.M. Silverman, 22 (2012). doi:10.1088/0004-637X/759/1/22 J. Hjorth, C. Thone,¨ A. Cucchiara, J.M.C. Ceron,´ A.J. Castro- A. Kappes, f.t. KM3NeT Consortium, KM3NeT: A Next Genera- Tirado, J.A. Arnold, M. Bremer, J.P. Brodie, T. Carroll, M.C. tion Neutrino Telescope in the Mediterranean Sea. ArXiv e-prints Cooper, P.A. Curran, R.M. Cutri, J. Ehle, D. Forbes, J. Fynbo, (2007) J. Gorosabel, J. Graham, D.I. Hoffman, S. Guziy, P. Jakobs- D. Kasen, Astrophysics: The supernova has two faces. Nature 466, 37– son, A. Kamble, T. Kerr, M.M. Kasliwal, C. Kouveliotou, D. 38 (2010). doi:10.1038/466037a Kocevski, N.M. Law, P.E. Nugent, E.O. Ofek, D. Poznanski, D. Kasen, R. Fernandez,´ B.D. Metzger, Kilonova light curves from R.M. Quimby, E. Rol, A.J. Romanowsky, R. Sanchez-Ram´ ´ırez, the disc wind outflows of compact object mergers. MNRAS 450, S. Schulze, N. Singh, L. van Spaandonk, R.L.C. Starling, R.G. 1777–1786 (2015). doi:10.1093/mnras/stv721 Strom, J.C. Tello, O. Vaduvescu, P.J. Wheatley, R.A.M.J. Wijers, A. Kathirgamaraju, R. Barniol Duran, D. Giannios, Off-axis short J.M. Winters, D. Xu, An Extremely Luminous Panchromatic Out- GRBs from structured jets as counterparts to GW events. ArXiv burst from the Nucleus of a Distant Galaxy. Science 333, 199 e-prints (2017) (2011). doi:10.1126/science.1207143 L. Keek, D.K. Galloway, J.J.M. in’t Zand, A. Heger, Multi-instrument A.J. Levan, N.R. Tanvir, A.S. Fruchter, J. Hjorth, E. Pian, P. Maz- X-ray Observations of Thermonuclear Bursts with Short Re- zali, R.A. Hounsell, D.A. Perley, Z. Cano, J. Graham, S.B. currence Times. ApJ 718, 292–305 (2010). doi:10.1088/0004- Cenko, J.P.U. Fynbo, C. Kouveliotou, A. Pe’er, K. Misra, K. 637X/718/1/292 Wiersema, Hubble Space Telescope Observations of the After- M.D. Kistler, H. Yuksel, A.M. Hopkins, The Cosmic Star Formation glow, Supernova, and Host Galaxy Associated with the Extremely Rate from the Faintest Galaxies in the Unobservable Universe. Bright GRB 130427A. ApJ 792, 115 (2014). doi:10.1088/0004- ArXiv e-prints (2013) 637X/792/2/115 S. Klimenko, G. Vedovato, M. Drago, G. Mazzolo, G. Mitsel- L.-X. Li, B. Paczynski,´ Transient Events from Neutron Star Mergers. makher, C. Pankow, G. Prodi, V. Re, F. Salemi, I. Yakushin, ApJ 507, 59–62 (1998). doi:10.1086/311680 Localization of gravitational wave sources with networks of W. Li, R. Chornock, J. Leaman, A.V. Filippenko, D. Poznanski, X. advanced detectors. Phys. Rev. D 83(10), 102001 (2011). Wang, M. Ganeshalingam, F. Mannucci, Nearby supernova rates doi:10.1103/PhysRevD.83.102001 from the Lick Observatory Supernova Search - III. The rate- Y. Kodama, D. Yonetoku, T. Murakami, S. Tanabe, R. Tsutsui, T. size relation, and the rates as a function of galaxy Hubble type Nakamura, Gamma-ray bursts in 1.8

S. Mereghetti, The strongest cosmic magnets: soft gamma-ray re- P.T. O’Brien, J.P. Osborne, P. Romano, G. Tagliaferri, A.A. peaters and anomalous X-ray pulsars. A&A Rev. 15, 225–287 Wells, Evidence for a Canonical Gamma-Ray Burst Afterglow (2008). doi:10.1007/s00159-008-0011-z Light Curve in the Swift XRT Data. ApJ 642, 389–400 (2006). C. Messenger, K. Takami, S. Gossan, L. Rezzolla, B.S. Sathyaprakash, doi:10.1086/500724 Source Redshifts from Gravitational-Wave Observations of Binary J.P. Osborne, Getting to know classical novae with Swift. Neutron Star Mergers. Physical Review X 4(4), 041004 (2014). Journal of High Energy Astrophysics 7, 117–125 (2015). doi:10.1103/PhysRevX.4.041004 doi:10.1016/j.jheap.2015.06.005 C. Messenger, H.J. Bulten, S.G. Crowder, V. Dergachev, D.K. Gal- J.P. Osborne, K.L. Page, A.P. Beardmore, M.F. Bode, M.R. Goad, loway, E. Goetz, R.J.G. Jonker, P.D. Lasky, G.D. Meadors, A. T.J. O’Brien, S. Starrfield, T. Rauch, J.-U. Ness, J. Krautter, G. Melatos, S. Premachandra, K. Riles, L. Sammut, E.H. Thrane, Schwarz, D.N. Burrows, N. Gehrels, J.J. Drake, A. Evans, S.P.S. J.T. Whelan, Y. Zhang, Gravitational waves from Scorpius X- Eyres, The Supersoft X-ray Phase of Nova RS Ophiuchi 2006. ApJ 1: A comparison of search methods and prospects for detection 727, 124 (2011). doi:10.1088/0004-637X/727/2/124 with advanced detectors. Phys. Rev. D 92(2), 023006 (2015). R.A. Osten, S. Drake, J. Tueller, J. Cummings, M. Perri, A. Moretti, doi:10.1103/PhysRevD.92.023006 S. Covino, Nonthermal Hard X-Ray Emission and Iron Kα Emis- P. Mesz´ aros,´ M.J. Rees, Population III Gamma-ray Bursts. ApJ 715, sion from a Superflare on II Pegasi. ApJ 654, 1052–1067 (2007). 967–971 (2010). doi:10.1088/0004-637X/715/2/967 doi:10.1086/509252 B.D. Metzger, E. Berger, What is the Most Promising Electromagnetic R.A. Osten, O. Godet, S. Drake, J. Tueller, J. Cummings, H. Krimm, Counterpart of a Neutron Star Binary Merger? ApJ 746, 48 (2012). J. Pye, V. Pal’shin, S. Golenetskii, F. Reale, S.R. Oates, M.J. Page, doi:10.1088/0004-637X/746/1/48 A. Melandri, The Mouse That Roared: A Superflare from the dMe B.D. Metzger, A.L. Piro, Optical and X-ray emission from sta- Flare Star EV Lac Detected by Swift and Konus-Wind. ApJ 721, ble millisecond magnetars formed from the merger of 785–801 (2010). doi:10.1088/0004-637X/721/1/785 binary neutron stars. MNRAS 439, 3916–3930 (2014). B. Paczynski,´ Are Gamma-Ray Bursts in Star-Forming Regions? ApJ doi:10.1093/mnras/stu247 494, 45–48 (1998). doi:10.1086/311148 M.J. Michałowski, G. Gentile, J. Hjorth, M.R. Krumholz, N.R. Tan- A.H. Patil, S. Zaroubi, E. Chapman, V. Jelic,´ G. Harker, F.B. Abdalla, vir, P. Kamphuis, D. Burlon, M. Baes, S. Basa, S. Berta, J.M. K.M.B. Asad, G. Bernardi, M.A. Brentjens, A.G. de Bruyn, S. Castro Ceron,´ D. Crosby, V. D’Elia, J. Elliott, J. Greiner, L.K. Bus, B. Ciardi, S. Daiboo, E.R. Fernandez, A. Ghosh, H. Jensen, Hunt, S. Klose, M.P. Koprowski, E. Le Floc’h, D. Malesani, T. S. Kazemi, L.V.E. Koopmans, P. Labropoulos, M. Mevius, O. Murphy, A. Nicuesa Guelbenzu, E. Palazzi, J. Rasmussen, A. Martinez, G. Mellema, A.R. Offringa, V.N. Pandey, J. Schaye, Rossi, S. Savaglio, P. Schady, J. Sollerman, A. de Ugarte Postigo, R.M. Thomas, H.K. Vedantham, V. Veligatla, S.J. Wijnholds, S. D. Watson, P. van der Werf, S.D. Vergani, D. Xu, Massive stars Yatawatta, Constraining the epoch of reionization with the vari- formed in atomic hydrogen reservoirs: H I observations of gamma- ance statistic: simulations of the LOFAR case. MNRAS 443, ray burst host galaxies. A&A 582, 78 (2015). doi:10.1051/0004- 1113–1124 (2014). doi:10.1093/mnras/stu1178 6361/201526542 D.A. Perley, N.R. Tanvir, J. Hjorth, T. Laskar, E. Berger, R. Chary, K. Mukai, M. Orio, M. Della Valle, Novae as a Class of Transient X- A. de Ugarte Postigo, J.P.U. Fynbo, T. Kruhler,¨ A.J. Levan, M.J. Ray Sources. ApJ 677, 1248–1252 (2008). doi:10.1086/529362 Michałowski, S. Schulze, The Swift GRB Host Galaxy Legacy R.F. Mushotzky, C. Done, K.A. Pounds, X-ray spectra and time vari- Survey. II. Rest-frame Near-IR Luminosity Distribution and Ev- ability of active galactic nuclei. ARA&A 31, 717–761 (1993). idence for a Near-solar Metallicity Threshold. ApJ 817, 8 (2016). doi:10.1146/annurev.astro.31.1.717 doi:10.3847/0004-637X/817/1/8 E. Nakar, R. Sari, Early Supernovae Light Curves Following the F. Perotti, C. Labanti, M. Marisaldi, F. Fuschino, L. Amati, B. Ne- Shock Breakout. ApJ 725, 904–921 (2010). doi:10.1088/0004- gri, H. Soltau, Silicon drift detectors array coupled to scintillators 637X/725/1/904 operated with pulse shape discrimination technique: a 1 keV - 1 E. Nakar, R. Sari, Relativistic Shock Breakouts - A Variety of MeV position sensitive gamma-ray detector, in High Energy, Op- Gamma-Ray Flares: From Low-luminosity Gamma-Ray Bursts tical, and Infrared Detectors for Astronomy III. Proc. SPIE, vol. to Type Ia Supernovae. ApJ 747, 88 (2012). doi:10.1088/0004- 7021, 2008, p. 70211. doi:10.1117/12.789474 637X/747/2/88 A. Pescalli, G. Ghirlanda, O.S. Salafia, G. Ghisellini, F. Nappo, P. Narayana Bhat, C.A. Meegan, A. von Kienlin, W.S. Paciesas, M.S. R. Salvaterra, Luminosity function and jet structure of Briggs, J.M. Burgess, E. Burns, V. Chaplin, W.H. Cleveland, A.C. Gamma-Ray Burst. MNRAS 447, 1911–1921 (2015). Collazzi, V. Connaughton, A.M. Diekmann, G. Fitzpatrick, M.H. doi:10.1093/mnras/stu2482 Gibby, M.M. Giles, A.M. Goldstein, J. Greiner, P.A. Jenke, R.M. A. Pescalli, G. Ghirlanda, R. Salvaterra, G. Ghisellini, S.D. Vergani, Kippen, C. Kouveliotou, B. Mailyan, S. McBreen, V. Pelassa, F. Nappo, O.S. Salafia, A. Melandri, S. Covino, D. Gotz,¨ The rate R.D. Preece, O.J. Roberts, L.S. Sparke, M. Stanbro, P. Veres, and luminosity function of long gamma ray bursts. A&A 587, 40 C.A. Wilson-Hodge, S. Xiong, G. Younes, H.-F. Yu, B. Zhang, (2016). doi:10.1051/0004-6361/201526760 The Third Fermi GBM Gamma-Ray Burst Catalog: The First Six V. Petrosian, E. Kitanidis, D. Kocevski, Cosmological Evolution of Years. ApJS 223, 28 (2016). doi:10.3847/0067-0049/223/2/28 Long Gamma-Ray Bursts and the Star Formation Rate. ApJ 806, D.B. Nestor, A.E. Shapley, K.A. Kornei, C.C. Steidel, B. Siana, A Re- 44 (2015). doi:10.1088/0004-637X/806/1/44 fined Estimate of the Ionizing Emissivity from Galaxies at z ˜= 3: E.S. Phinney, Finding and Using Electromagnetic Counterparts of Spectroscopic Follow-up in the SSA22a Field. ApJ 765, 47 (2013). Gravitational Wave Sources, in astro2010: The Astronomy and doi:10.1088/0004-637X/765/1/47 Astrophysics Decadal Survey. ArXiv Astrophysics e-prints, vol. S. Nissanke, D.E. Holz, S.A. Hughes, N. Dalal, J.L. Sievers, Exploring 2010, 2009 Short Gamma-ray Bursts as Gravitational-wave Standard Sirens. A.L. Piro, B. Giacomazzo, R. Perna, The Fate of Neutron Star Binary ApJ 725, 496–514 (2010). doi:10.1088/0004-637X/725/1/496 Mergers. ApJ 844, 19 (2017). doi:10.3847/2041-8213/aa7f2f J.A. Nousek, C. Kouveliotou, D. Grupe, K.L. Page, J. Granot, Planck Collaboration, R. Adam, N. Aghanim, M. Ashdown, J. Au- E. Ramirez-Ruiz, S.K. Patel, D.N. Burrows, V. Mangano, S. mont, C. Baccigalupi, M. Ballardini, A.J. Banday, R.B. Barreiro, Barthelmy, A.P. Beardmore, S. Campana, M. Capalbi, G. Chin- N. Bartolo, S. Basak, R. Battye, K. Benabed, J.-P. Bernard, M. carini, G. Cusumano, A.D. Falcone, N. Gehrels, P. Giommi, Bersanelli, P. Bielewicz, J.J. Bock, A. Bonaldi, L. Bonavera, J.R. M.R. Goad, O. Godet, C.P. Hurkett, J.A. Kennea, A. Moretti, Bond, J. Borrill, F.R. Bouchet, F. Boulanger, M. Bucher, C. Buri- 54 Amati et al.

gana, E. Calabrese, J.-F. Cardoso, J. Carron, H.C. Chiang, L.P.L. 43–74 (2009). doi:10.1088/0004-637X/698/1/43 Colombo, C. Combet, B. Comis, F. Couchot, A. Coulais, B.P. Crill, N. Rea, M. Gullon,´ J.A. Pons, R. Perna, M.G. Dainotti, J.A. Mi- A. Curto, F. Cuttaia, R.J. Davis, P. de Bernardis, A. de Rosa, G. de ralles, D.F. Torres, Constraining the GRB-Magnetar Model by Zotti, J. Delabrouille, E. Di Valentino, C. Dickinson, J.M. Diego, Means of the Galactic Pulsar Population. ApJ 813, 92 (2015). O. Dore,´ M. Douspis, A. Ducout, X. Dupac, F. Elsner, T.A. Enßlin, doi:10.1088/0004-637X/813/2/92 H.K. Eriksen, E. Falgarone, Y. Fantaye, F. Finelli, F. Forastieri, F. Reale, Diagnostics of stellar flares from X-ray observations: M. Frailis, A.A. Fraisse, E. Franceschi, A. Frolov, S. Galeotta, S. from the decay to the rise phase. A&A 471, 271–279 (2007). Galli, K. Ganga, R.T. Genova-Santos,´ M. Gerbino, T. Ghosh, J. doi:10.1051/0004-6361:20077223 Gonzalez-Nuevo,´ K.M. Gorski,´ A. Gruppuso, J.E. Gudmundsson, M.J. Rees, Tidal disruption of stars by black holes of 10 to the 6th-10 F.K. Hansen, G. Helou, S. Henrot-Versille,´ D. Herranz, E. Hivon, to the 8th solar masses in nearby galaxies. Nature 333, 523–528 Z. Huang, S. Ilic,´ A.H. Jaffe, W.C. Jones, E. Keihanen,¨ R. Keski- (1988). doi:10.1038/333523a0 talo, T.S. Kisner, L. Knox, N. Krachmalnicoff, M. Kunz, H. Kurki- L. Rezzolla, P. Kumar, A Novel Paradigm for Short Gamma-Ray Suonio, G. Lagache, A. Lahteenm¨ aki,¨ J.-M. Lamarre, M. Langer, Bursts With Extended X-Ray Emission. ApJ 802, 95 (2015). A. Lasenby, M. Lattanzi, C.R. Lawrence, M. Le Jeune, F. Levrier, doi:10.1088/0004-637X/802/2/95 A. Lewis, M. Liguori, P.B. Lilje, M. Lopez-Caniego,´ Y.-Z. Ma, L. Rezzolla, K. Takami, Gravitational-wave signal from binary neutron J.F. Mac´ıas-Perez,´ G. Maggio, A. Mangilli, M. Maris, P.G. Mar- stars: A systematic analysis of the spectral properties. Phys. Rev. D tin, E. Mart´ınez-Gonzalez,´ S. Matarrese, N. Mauri, J.D. McEwen, 93(12), 124051 (2016). doi:10.1103/PhysRevD.93.124051 P.R. Meinhold, A. Melchiorri, A. Mennella, M. Migliaccio, M.-A. L. Rezzolla, B. Giacomazzo, L. Baiotti, J. Granot, C. Kouveliotou, Miville-Deschenes,ˆ D. Molinari, A. Moneti, L. Montier, G. Mor- M.A. Aloy, The Missing Link: Merging Neutron Stars Natu- gante, A. Moss, P. Naselsky, P. Natoli, C.A. Oxborrow, L. Pagano, rally Produce Jet-like Structures and Can Power Short Gamma-ray D. Paoletti, B. Partridge, G. Patanchon, L. Patrizii, O. Perdereau, Bursts. ApJ 732, 6 (2011). doi:10.1088/2041-8205/732/1/L6 L. Perotto, V. Pettorino, F. Piacentini, S. Plaszczynski, L. Polas- B.E. Robertson, R.S. Ellis, Connecting the Gamma Ray Burst Rate tri, G. Polenta, J.-L. Puget, J.P. Rachen, B. Racine, M. Reinecke, and the Cosmic Star Formation History: Implications for Reioniza- M. Remazeilles, A. Renzi, G. Rocha, M. Rossetti, G. Roudier, tion and Galaxy Evolution. ApJ 744, 95 (2012). doi:10.1088/0004- J.A. Rubino-Mart˜ ´ın, B. Ruiz-Granados, L. Salvati, M. Sandri, M. 637X/744/2/95 Savelainen, D. Scott, G. Sirri, R. Sunyaev, A.-S. Suur-Uski, J.A. B.E. Robertson, S.R. Furlanetto, E. Schneider, S. Charlot, R.S. El- Tauber, M. Tenti, L. Toffolatti, M. Tomasi, M. Tristram, T. Trom- lis, D.P. Stark, R.J. McLure, J.S. Dunlop, A. Koekemoer, M.A. betti, J. Valiviita, F. Van Tent, P. Vielva, F. Villa, N. Vittorio, B.D. Schenker, M. Ouchi, Y. Ono, E. Curtis-Lake, A.B. Rogers, R.A.A. Wandelt, I.K. Wehus, M. White, A. Zacchei, A. Zonca, Planck in- Bowler, M. Cirasuolo, New Constraints on Cosmic Reionization termediate results. XLVII. Planck constraints on reionization his- from the 2012 Hubble Ultra Deep Field Campaign. ApJ 768, 71 tory. A&A 596, 108 (2016). doi:10.1051/0004-6361/201628897 (2013). doi:10.1088/0004-637X/768/1/71 M. Punturo, M. Abernathy, F. Acernese, B. Allen, N. Andersson, K. P. Romano, E. Bozzo, V. Mangano, P. Esposito, G. Israel, A. Tiengo, Arun, F. Barone, B. Barr, M. Barsuglia, M. Beker, N. Beveridge, S. Campana, L. Ducci, C. Ferrigno, J.A. Kennea, Giant outburst S. Birindelli, S. Bose, L. Bosi, S. Braccini, C. Bradaschia, T. Bu- from the supergiant fast X-ray transient IGR J17544-2619: accre- lik, E. Calloni, G. Cella, E. Chassande Mottin, S. Chelkowski, A. tion from a transient disc? A&A 576, 4 (2015). doi:10.1051/0004- Chincarini, J. Clark, E. Coccia, C. Colacino, J. Colas, A. Cum- 6361/201525749 ming, L. Cunningham, E. Cuoco, S. Danilishin, K. Danzmann, G. A. Rossi, S. Schulze, S. Klose, D.A. Kann, A. Rau, H.A. Krimm, G. De Luca, R. De Salvo, T. Dent, R. De Rosa, L. Di Fiore, A. Di Johannesson,´ A. Panaitescu, F. Yuan, P. Ferrero, T. Kruhler,¨ J. Virgilio, M. Doets, V. Fafone, P. Falferi, R. Flaminio, J. Franc, Greiner, P. Schady, S.B. Pandey, L. Amati, P.M.J. Afonso, C.W. F. Frasconi, A. Freise, P. Fulda, J. Gair, G. Gemme, A. Gennai, Akerlof, L.A. Arnold, C. Clemens, R. Filgas, D.H. Hartmann, A. A. Giazotto, K. Glampedakis, M. Granata, H. Grote, G. Guidi, Kupc¨ u¨ Yoldas¸, S. McBreen, T.A. McKay, A. Nicuesa Guelbenzu, G. Hammond, M. Hannam, J. Harms, D. Heinert, M. Hendry, F.E. Olivares, B. Paciesas, E.S. Rykoff, G. Szokoly, A.C. Updike, I. Heng, E. Hennes, S. Hild, J. Hough, S. Husa, S. Huttner, G. A. Yoldas¸, The Swift/Fermi GRB 080928 from 1 eV to 150 keV. Jones, F. Khalili, K. Kokeyama, K. Kokkotas, B. Krishnan, M. A&A 529, 142 (2011). doi:10.1051/0004-6361/201015324 Lorenzini, H. Luck,¨ E. Majorana, I. Mandel, V. Mandic, I. Mar- A. Rossi, S. Klose, P. Ferrero, J. Greiner, L.A. Arnold, E. Gonsalves, tin, C. Michel, Y. Minenkov, N. Morgado, S. Mosca, B. Mours, H. D.H. Hartmann, A.C. Updike, D.A. Kann, T. Kruhler,¨ E. Palazzi, Muller-Ebhardt,¨ P. Murray, R. Nawrodt, J. Nelson, R. Oshaugh- S. Savaglio, S. Schulze, P.M.J. Afonso, L. Amati, A.J. Castro- nessy, C.D. Ott, C. Palomba, A. Paoli, G. Parguez, A. Pasqualetti, Tirado, C. Clemens, R. Filgas, J. Gorosabel, L.K. Hunt, A. Kupc¨ u¨ R. Passaquieti, D. Passuello, L. Pinard, R. Poggiani, P. Popolizio, Yoldas¸, N. Masetti, M. Nardini, A. Nicuesa Guelbenzu, F.E. Oli- M. Prato, P. Puppo, D. Rabeling, P. Rapagnani, J. Read, T. Regim- vares, E. Pian, A. Rau, P. Schady, S. Schmidl, A. Yoldas¸, A. de bau, H. Rehbein, S. Reid, L. Rezzolla, F. Ricci, F. Richard, A. Ugarte Postigo, A deep search for the host galaxies of gamma-ray Rocchi, S. Rowan, A. Rudiger,¨ B. Sassolas, B. Sathyaprakash, R. bursts with no detected optical afterglow. A&A 545, 77 (2012). Schnabel, C. Schwarz, P. Seidel, A. Sintes, K. Somiya, F. Speir- doi:10.1051/0004-6361/201117201 its, K. Strain, S. Strigin, P. Sutton, S. Tarabrin, A. Thuring,¨ J. van A. Rowlinson, B.P. Gompertz, M. Dainotti, P.T. O’Brien, R.A.M.J. den Brand, C. van Leewen, M. van Veggel, C. van den Broeck, A. Wijers, A.J. van der Horst, Constraining properties of GRB Vecchio, J. Veitch, F. Vetrano, A. Vicere, S. Muller¨ Vyatchanin, B. magnetar central engines using the observed plateau luminos- Willke, G. Woan, P. Wolfango, K. Yamamoto, The Einstein Tele- ity and duration correlation. MNRAS 443, 1779–1787 (2014). scope: a third-generation gravitational wave observatory. Classical doi:10.1093/mnras/stu1277 and Quantum Gravity 27(19), 194002 (2010). doi:10.1088/0264- F. Ryde, M. Axelsson, B.B. Zhang, S. McGlynn, A. Pe’er, C. Lund- 9381/27/19/194002 man, S. Larsson, M. Battelino, B. Zhang, E. Bissaldi, J. Bre- J.P. Pye, I.M. McHardy, The Ariel V sky survey of fast- geon, M.S. Briggs, J. Chiang, F. de Palma, S. Guiriec, J. Lars- transient X-ray sources. MNRAS 205, 875–888 (1983). son, F. Longo, S. McBreen, N. Omodei, V. Petrosian, R. Preece, doi:10.1093/mnras/205.3.875 A.J. van der Horst, Identification and Properties of the Photo- J.L. Racusin, E.W. Liang, D.N. Burrows, A. Falcone, T. Sakamoto, spheric Emission in GRB090902B. ApJ 709, 172–177 (2010). B.B. Zhang, B. Zhang, P. Evans, J. Osborne, Jet Breaks and En- doi:10.1088/2041-8205/709/2/L172 ergetics of Swift Gamma-Ray Burst X-Ray Afterglows. ApJ 698, T. Sakamoto, D.Q. Lamb, N. Kawai, A. Yoshida, C. Graziani, E.E. Fen- THESEUS 55

imore, T.Q. Donaghy, M. Matsuoka, M. Suzuki, G. Ricker, J.-L. ley, X.-Y. Wang, E.O. Ofek, A. Cucchiara, A. Rau, E. Waxman, Atteia, Y. Shirasaki, T. Tamagawa, K. Torii, M. Galassi, J. Doty, R. J.D. Simon, D.C.-J. Bock, P.A. Milne, M.J. Page, J.C. Barentine, Vanderspek, G.B. Crew, J. Villasenor, N. Butler, G. Prigozhin, J.G. S.D. Barthelmy, A.P. Beardmore, M.F. Bietenholz, P. Brown, A. Jernigan, C. Barraud, M. Boer, J.-P. Dezalay, J.-F. Olive, K. Hur- Burrows, D.N. Burrows, G. Byrngelson, S.B. Cenko, P. Chandra, ley, A. Levine, G. Monnelly, F. Martel, E. Morgan, S.E. Woosley, J.R. Cummings, D.B. Fox, A. Gal-Yam, N. Gehrels, S. Immler, T. Cline, J. Braga, R. Manchanda, G. Pizzichini, K. Takagishi, M. M. Kasliwal, A.K.H. Kong, H.A. Krimm, S.R. Kulkarni, T.J. Mac- Yamauchi, Global Characteristics of X-Ray Flashes and X-Ray- carone, P. Mesz´ aros,´ E. Nakar, P.T. O’Brien, R.A. Overzier, M. de Rich Gamma-Ray Bursts Observed by HETE-2. ApJ 629, 311– Pasquale, J. Racusin, N. Rea, D.G. York, An extremely luminous 327 (2005). doi:10.1086/431235 X-ray outburst at the birth of a supernova. Nature 453, 469–474 R. Salvaterra, S. Campana, S.D. Vergani, S. Covino, P. D’Avanzo, (2008). doi:10.1038/nature06997 D. Fugazza, G. Ghirlanda, G. Ghisellini, A. Melandri, L. Nava, A.M. Soderberg, S. Chakraborti, G. Pignata, R.A. Chevalier, P. Chan- B. Sbarufatti, H. Flores, S. Piranomonte, G. Tagliaferri, A Com- dra, A. Ray, M.H. Wieringa, A. Copete, V. Chaplin, V. Con- plete Sample of Bright Swift Long Gamma-Ray Bursts. I. Sam- naughton, S.D. Barthelmy, M.F. Bietenholz, N. Chugai, M.D. ple Presentation, Luminosity Function and Evolution. ApJ 749, 68 Stritzinger, M. Hamuy, C. Fransson, O. Fox, E.M. Levesque, J.E. (2012). doi:10.1088/0004-637X/749/1/68 Grindlay, P. Challis, R.J. Foley, R.P. Kirshner, P.A. Milne, M.A.P. R. Salvaterra, U. Maio, B. Ciardi, M.A. Campisi, Simulating high-z Torres, A relativistic type Ibc supernova without a detected γ-ray gamma-ray burst host galaxies. MNRAS 429, 2718–2726 (2013). burst. Nature 463, 513–515 (2010). doi:10.1038/nature08714 doi:10.1093/mnras/sts541 J.L. Sokoloski, S.J. Kenyon, B.R. Espey, C.D. Keyes, S.R. McCan- M. Santander, The Dawn of Multi-Messenger Astronomy. ArXiv e- dliss, A.K.H. Kong, J.P. Aufdenberg, A.V. Filippenko, W. Li, C. prints (2016) Brocksopp, C.R. Kaiser, P.A. Charles, M.P. Rupen, R.P.S. Stone, R. Sari, T. Piran, Predictions for the Very Early Afterglow and the Op- A “Combination Nova” Outburst in Z Andromedae: Nuclear Shell tical Flash. ApJ 520, 641–649 (1999). doi:10.1086/307508 Burning Triggered by a Disk Instability. ApJ 636, 1002–1019 B. Sathyaprakash, M. Abernathy, F. Acernese, P. Ajith, B. Allen, (2006). doi:10.1086/498206 P. Amaro-Seoane, N. Andersson, S. Aoudia, K. Arun, P. As- M. Sparre, O.E. Hartoog, T. Kruhler,¨ J.P.U. Fynbo, D.J. Watson, K. tone, et al., Scientific objectives of Einstein Telescope. Classical Wiersema, V. D’Elia, T. Zafar, P.M.J. Afonso, S. Covino, A. and Quantum Gravity 29(12), 124013 (2012). doi:10.1088/0264- de Ugarte Postigo, H. Flores, P. Goldoni, J. Greiner, J. Hjorth, 9381/29/12/124013 P. Jakobsson, L. Kaper, S. Klose, A.J. Levan, D. Malesani, B. S. Savaglio, K. Glazebrook, D. Le Borgne, The Galaxy Popula- Milvang-Jensen, M. Nardini, S. Piranomonte, J. Sollerman, R. tion Hosting Gamma-Ray Bursts. ApJ 691, 182–211 (2009). Sanchez-Ram´ ´ırez, S. Schulze, N.R. Tanvir, S.D. Vergani, R.A.M.J. doi:10.1088/0004-637X/691/1/182 Wijers, The Metallicity and Dust Content of a Redshift 5 Gamma- M.A. Schenker, R.S. Ellis, N.P. Konidaris, D.P. Stark, Line-emitting Ray Burst Host Galaxy. ApJ 785, 150 (2014). doi:10.1088/0004- Galaxies beyond a Redshift of 7: An Improved Method for Esti- 637X/785/2/150 mating the Evolving Neutrality of the Intergalactic Medium. ApJ R.L.C. Starling, K. Wiersema, A.J. Levan, T. Sakamoto, D. Bersier, 795, 20 (2014). doi:10.1088/0004-637X/795/1/20 P. Goldoni, S.R. Oates, A. Rowlinson, S. Campana, J. Sollerman, S. Schulze, S. Klose, G. Bjornsson,¨ P. Jakobsson, D.A. Kann, A. Rossi, N.R. Tanvir, D. Malesani, J.P.U. Fynbo, S. Covino, P. D’Avanzo, T. Kruhler,¨ J. Greiner, P. Ferrero, The circumburst density profile P.T. O’Brien, K.L. Page, J.P. Osborne, S.D. Vergani, S. Barthelmy, around GRB progenitors: a statistical study. A&A 526, 23 (2011). D.N. Burrows, Z. Cano, P.A. Curran, M. de Pasquale, V. D’Elia, doi:10.1051/0004-6361/201015581 P.A. Evans, H. Flores, A.S. Fruchter, P. Garnavich, N. Gehrels, J. S. Schulze, T. Kruhler,¨ G. Leloudas, J. Gorosabel, A. Mehner, J. Buch- Gorosabel, J. Hjorth, S.T. Holland, A.J. van der Horst, C.P. Hur- ner, S. Kim, E. Ibar, R. Amor´ın, R. Herrero-Illana, J.P. Anderson, kett, P. Jakobsson, A.P. Kamble, C. Kouveliotou, N.P.M. Kuin, L. F.E. Bauer, L. Christensen, M. de Pasquale, A. de Ugarte Postigo, Kaper, P.A. Mazzali, P.E. Nugent, E. Pian, M. Stamatikos, C.C. A. Gallazzi, J. Hjorth, N. Morrell, D. Malesani, M. Sparre, B. Thone,¨ S.E. Woosley, Discovery of the nearby long, soft GRB Stalder, A.A. Stark, C.C. Thone,¨ J.C. Wheeler, Cosmic evolu- 100316D with an associated supernova. MNRAS 411, 2792–2803 tion and metal aversion in super-luminous supernova host galaxies. (2011). doi:10.1111/j.1365-2966.2010.17879.x ArXiv e-prints (2016) S. Starrfield, C. Iliadis, W.R. Hix, F.X. Timmes, W.M. Sparks, The B.F. Schutz, Determining the Hubble constant from gravitational wave Effects of the pep Nuclear Reaction and Other Improvements in observations. Nature 323, 310 (1986). doi:10.1038/323310a0 the Nuclear Reaction Rate Library on Simulations of the Classical G.J. Schwarz, J.-U. Ness, J.P. Osborne, K.L. Page, P.A. Evans, A.P. Nova Outburst. ApJ 692, 1532–1542 (2009). doi:10.1088/0004- Beardmore, F.M. Walter, L.A. Helton, C.E. Woodward, M. Bode, 637X/692/2/1532 S. Starrfield, J.J. Drake, Swift X-Ray Observations of Classical G. Stratta, B. Gendre, J.L. Atteia, M. Boer,¨ D.M. Coward, M. De Novae. II. The Super Soft Source Sample. ApJS 197, 31 (2011). Pasquale, E. Howell, A. Klotz, S. Oates, L. Piro, The Ultra-long doi:10.1088/0067-0049/197/2/31 GRB 111209A. II. Prompt to Afterglow and Afterglow Properties. D.M. Siegel, R. Ciolfi, Electromagnetic Emission from Long-lived Bi- ApJ 779, 66 (2013). doi:10.1088/0004-637X/779/1/66 nary Neutron Star Merger Remnants. I. Formulation of the Prob- T.E. Strohmayer, A.L. Watts, The 2004 Hyperflare from SGR 1806- lem. ApJ 819, 14 (2016a). doi:10.3847/0004-637X/819/1/14 20: Further Evidence for Global Torsional Vibrations. ApJ 653, D.M. Siegel, R. Ciolfi, Electromagnetic Emission from Long-lived Bi- 593–601 (2006). doi:10.1086/508703 nary Neutron Star Merger Remnants. II. Lightcurves and Spectra. M. Sullivan, J. Guy, A. Conley, N. Regnault, P. Astier, C. Balland, ApJ 819, 15 (2016b). doi:10.3847/0004-637X/819/1/15 S. Basa, R.G. Carlberg, D. Fouchez, D. Hardin, I.M. Hook, D.A. L.P. Singer, H.-Y. Chen, D.E. Holz, W.M. Farr, L.R. Price, V. Ray- Howell, R. Pain, N. Palanque-Delabrouille, K.M. Perrett, C.J. mond, S.B. Cenko, N. Gehrels, J. Cannizzo, M.M. Kasliwal, S. Pritchet, J. Rich, V. Ruhlmann-Kleider, D. Balam, S. Baumont, Nissanke, M. Coughlin, B. Farr, A.L. Urban, S. Vitale, J. Veitch, P. R.S. Ellis, S. Fabbro, H.K. Fakhouri, N. Fourmanoit, S. Gonzalez-´ Graff, C.P.L. Berry, S. Mohapatra, I. Mandel, Going the Distance: Gaitan,´ M.L. Graham, M.J. Hudson, E. Hsiao, T. Kronborg, C. Mapping Host Galaxies of LIGO and Virgo Sources in Three Di- Lidman, A.M. Mourao, J.D. Neill, S. Perlmutter, P. Ripoche, N. mensions Using Local Cosmography and Targeted Follow-up. ApJ Suzuki, E.S. Walker, SNLS3: Constraints on Dark Energy Com- 829, 15 (2016). doi:10.3847/2041-8205/829/1/L15 bining the Supernova Legacy Survey Three-year Data with Other A.M. Soderberg, E. Berger, K.L. Page, P. Schady, J. Parrent, D. Poo- Probes. ApJ 737, 102 (2011). doi:10.1088/0004-637X/737/2/102 56 Amati et al.

D. Szecsi,´ How may short-duration GRBs form? A review of pro- Distances. ApJ 842, 47 (2017a). doi:10.3847/1538-4357/aa74ae genitor theories. Contributions of the Astronomical Observatory E. Vanzella, F. Calura, M. Meneghetti, A. Mercurio, M. Castellano, Skalnate Pleso 47, 108–115 (2017) G.B. Caminha, I. Balestra, P. Rosati, P. Tozzi, S. De Barros, A. D. Szecsi,´ N. Langer, S.-C. Yoon, D. Sanyal, S. de Mink, C.J. Evans, T. Grazian, A. D’Ercole, L. Ciotti, K. Caputi, C. Grillo, E. Merlin, Dermine, Low-metallicity massive single stars with rotation. Evo- L. Pentericci, A. Fontana, S. Cristiani, D. Coe, Paving the way for lutionary models applicable to I Zwicky 18. A&A 581, 15 (2015). the JWST: witnessing globular cluster formation at z 3. MNRAS doi:10.1051/0004-6361/201526617 467, 4304–4321 (2017b). doi:10.1093/mnras/stx351 K. Takami, L. Rezzolla, L. Baiotti, Constraining the Equation of State S.D. Vergani, J. Palmerio, R. Salvaterra, J. Japelj, F. Mannucci, D.A. of Neutron Stars from Binary Mergers. Physical Review Letters Perley, P. D’Avanzo, T. Kruhler,¨ M. Puech, S. Boissier, S. Cam- 113(9), 091104 (2014). doi:10.1103/PhysRevLett.113.091104 pana, S. Covino, L.K. Hunt, P. Petitjean, G. Tagliaferri, The chem- N.R. Tanvir, A.J. Levan, A.S. Fruchter, J.P.U. Fynbo, J. Hjorth, K. ical enrichment of long gamma-ray bursts nurseries up to z = 2. Wiersema, M.N. Bremer, J. Rhoads, P. Jakobsson, P.T. O’Brien, A&A 599, 120 (2017). doi:10.1051/0004-6361/201629759 E.R. Stanway, D. Bersier, P. Natarajan, J. Greiner, D. Watson, D. Wanderman, T. Piran, The rate, luminosity function and time delay A.J. Castro-Tirado, R.A.M.J. Wijers, R.L.C. Starling, K. Misra, of non-Collapsar short GRBs. MNRAS 448, 3026–3037 (2015). J.F. Graham, C. Kouveliotou, Star Formation in the Early Uni- doi:10.1093/mnras/stv123 verse: Beyond the Tip of the Iceberg. ApJ 754, 46 (2012). E. Waxman, J. Bahcall, High Energy Neutrinos from Cosmological doi:10.1088/0004-637X/754/1/46 Gamma-Ray Burst Fireballs. Physical Review Letters 78, 2292– N.R. Tanvir, A.J. Levan, A.S. Fruchter, J. Hjorth, R.A. Hounsell, 2295 (1997). doi:10.1103/PhysRevLett.78.2292 K. Wiersema, R.L. Tunnicliffe, A ‘kilonova’ associated with the R. Willingale, P. Mesz´ aros,´ Gamma-Ray Bursts and Fast Tran- short-duration γ-ray burst GRB 130603B. Nature 500, 547–549 sients. Multi-wavelength Observations and Multi-messenger Sig- (2013). doi:10.1038/nature12505 nals. Space Sci. Rev. 207, 63–86 (2017). doi:10.1007/s11214-017- C. Thompson, R.C. Duncan, The soft gamma repeaters as very strongly 0366-4 magnetized neutron stars - I. Radiative mechanism for outbursts. S.E. Woosley, Gamma-ray bursts from stellar mass accre- MNRAS 275, 255–300 (1995). doi:10.1093/mnras/275.2.255 tion disks around black holes. ApJ 405, 273–277 (1993). A. Tramacere, P. Giommi, E. Massaro, M. Perri, R. Nesci, S. Co- doi:10.1086/172359 lafrancesco, G. Tagliaferri, G. Chincarini, A. Falcone, D.N. Bur- D. Yonetoku, T. Murakami, T. Nakamura, R. Yamazaki, A.K. Inoue, K. rows, P. Roming, M. McMath Chester, N. Gehrels, SWIFT obser- Ioka, Gamma-Ray Burst Formation Rate Inferred from the Spec- vations of TeV BL Lacertae objects. A&A 467, 501–508 (2007). tral Peak Energy-Peak Luminosity Relation. ApJ 609, 935–951 doi:10.1051/0004-6361:20066226 (2004). doi:10.1086/421285 E. Troja, T. Sakamoto, S.B. Cenko, A. Lien, N. Gehrels, A.J. Castro- D. Yonetoku, T. Mihara, T. Sawano, H. Ikeda, A. Harayama, S. Tirado, R. Ricci, J. Capone, V. Toy, A. Kutyrev, N. Kawai, A. Cuc- Takata, K. Yoshida, H. Seta, A. Toyanago, Y. Kagawa, K. Kawai, chiara, A. Fruchter, J. Gorosabel, S. Jeong, A. Levan, D. Perley, R. N. Kawai, T. Sakamoto, M. Serino, S. Kurosawa, S. Gunji, T. Sanchez-Ramirez, N. Tanvir, S. Veilleux, An Achromatic Break in Tanimori, T. Murakami, Y. Yatsu, K. Yamaoka, A. Yoshida, K. the Afterglow of the Short GRB 140903A: Evidence for a Narrow Kawabata, T. Matsumoto, K. Tsumura, S. Matsuura, M. Shira- Jet. ApJ 827, 102 (2016). doi:10.3847/0004-637X/827/2/102 hata, H. Okita, K. Yanagisawa, M. Yoshida, K. Motohara, High- E. Troja, V.M. Lipunov, C.G. Mundell, N.R. Butler, A.M. Watson, S. z gamma-ray bursts for unraveling the dark ages mission HiZ- Kobayashi, S.B. Cenko, F.E. Marshall, R. Ricci, A. Fruchter, M.H. GUNDAM, in Space Telescopes and Instrumentation 2014: Ul- Wieringa, E.S. Gorbovskoy, V. Kornilov, A. Kutyrev, W.H. Lee, V. traviolet to Gamma Ray. Proc. SPIE, vol. 9144, 2014, p. 91442. Toy, N.V. Tyurina, N.M. Budnev, D.A.H. Buckley, J. Gonzalez, doi:10.1117/12.2055041 O. Gress, A. Horesh, M.I. Panasyuk, J.X. Prochaska, E. Ramirez- S.-C. Yoon, A. Dierks, N. Langer, Evolution of massive Population Ruiz, R. Rebolo Lopez, M.G. Richer, C. Roman-Zuniga, M. Serra- III stars with rotation and magnetic fields. A&A 542, 113 (2012). Ricart, V. Yurkov, N. Gehrels, Significant and variable linear po- doi:10.1051/0004-6361/201117769 larization during the prompt optical flash of GRB 160625B. Nature S.-C. Yoon, N. Langer, C. Norman, Single star progenitors of 547, 425–427 (2017) long gamma-ray bursts. I. Model grids and redshift depen- Y. Ueda, Y. Ishisaki, T. Takahashi, K. Makishima, T. Ohashi, dent GRB rate. A&A 460, 199–208 (2006). doi:10.1051/0004- The ASCA Medium Sensitivity Survey (The GIS Catalog 6361:20065912 Project): Source Catalog II. ApJS 161, 185–223 (2005). B. Zhang, Early X-Ray and Optical Afterglow of Gravitational Wave doi:10.1086/468187 Bursts from Mergers of Binary Neutron Stars. ApJ 763, 22 (2013). H. van Eerten, W. Zhang, A. MacFadyen, Off-axis Gamma-ray doi:10.1088/2041-8205/763/1/L22 Burst Afterglow Modeling Based on a Two-dimensional Axisym- B. Zhang, P. Mesz´ aros,´ Gamma-Ray Burst Afterglow with Continuous metric Hydrodynamics Simulation. ApJ 722, 235–247 (2010). Energy Injection: Signature of a Highly Magnetized Millisecond doi:10.1088/0004-637X/722/1/235 Pulsar. ApJ 552, 35–38 (2001). doi:10.1086/320255 M.H.P.M. van Putten, C. Guidorzi, F. Frontera, Broadband Turbulent B. Zhang, B.-B. Zhang, E.-W. Liang, N. Gehrels, D.N. Burrows, P. Spectra in Gamma-Ray Burst Light Curves. ApJ 786, 146 (2014). Mesz´ aros,´ Making a Short Gamma-Ray Burst from a Long One: doi:10.1088/0004-637X/786/2/146 Implications for the Nature of GRB 060614. ApJ 655, 25–28 M.H.P.M. van Putten, A. Levinson, F. Frontera, C. Guidorzi, L. Amati, (2007). doi:10.1086/511781 M. Della Valle, GPU-searches for broadband extended emission in gravitational waves in nearby energetic core-collapse supernovae. ArXiv e-prints (2017) E. Vanzella, M. Castellano, M. Meneghetti, A. Mercurio, G.B. Cam- inha, G. Cupani, F. Calura, L. Christensen, E. Merlin, P. Rosati, M. Gronke, M. Dijkstra, M. Mignoli, R. Gilli, S. De Barros, K. Ca- puti, C. Grillo, I. Balestra, S. Cristiani, M. Nonino, E. Giallongo, A. Grazian, L. Pentericci, A. Fontana, A. Comastri, C. Vignali, G. Zamorani, M. Brusa, P. Bergamini, P. Tozzi, Magnifying the Early Episodes of Star Formation: Super Star Clusters at Cosmological