PoS(ICRC2021)652 International th 12–23 July 2021 July 12–23 37 SICS CONFERENCE SICS CONFERENCE Berlin | Germany Berlin Berlin | Germany Cosmic Ray Conference Ray Cosmic ICRC 2021 THE ASTROPARTICLE PHY ICRC 2021 THEASTROPARTICLE PHY https://pos.sissa.it/ ONLINE 50% of the sky. We have completed a Phase > 25% of the sky, and they are surrounded on the sides > on behalf of the COSI Collaboration ∗ 0, [email protected] International Cosmic Ray Conference (ICRC 2021) Presenter ∗ th Space Sciences Laboratory, 7 Gauss Way, UniversityE-mail: of California, Berkeley, CA 94720-7450, USA The Compton Spectrometer andof Imager imaging, spectroscopy, (COSI) and polarimetry ispossible of a by COSI’s astrophysical germanium sources. 0.2–5 cross-strip MeV detectors, which Such Compton provide high capabilities efficiency,spectroscopy high telescope resolution are and made capable precise 3D positioning ofstudies photon of interactions. 0.511 MeV Science emission goals from forelements COSI antimatter from include annihilation nucleosynthesis, in determining the Galaxy, emissionpolarization, mapping mechanisms and radioactive and detecting source and geometriesview localizing with (FOV) for multimessenger the sources. germanium detectors is The instantaneous field of and bottom by active shields, providing backgroundgamma-ray rejection bursts as or well other as gamma-ray allowing flares for over detection of A concept study to considerdiscuss COSI the as advances COSI-SMEX a provides Small for astrophysics Explorer in (SMEX) the MeV satellite bandpass. mission, and here we Copyright owned by the author(s) under the terms of the Creative Commons 0 © Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). John A. Tomsick (a complete list of authors can be found at the end of the proceedings) The Compton Spectrometer and Imager ProjectAstronomy for MeV 37 July 12th – 23rd, 2021 Online – Berlin, Germany PoS(ICRC2021)652 Al with 26 John A. Tomsick 90% of its time in > Fe, search for young, hidden supernova 60 South of zenith every 12 hours to enable Fe provide a look at where in the Galaxy ◦ 60 COSI (yellow rectangles) is shown in a low- 22 2 Al and 26 Figure 1: inclination low-Earth orbit.entire sky In on daily survey time mode, scales viaing it North-South the repointing. monitors Dur- prime the mission, COSI will spend survey mode. North of zenith to ◦ 22 90 K. They < Ti emission, and enable a host of other nuclear astrophysics studies. COSI Al is also thought to be produced (and released) in the winds of massive stars. 44 26 The Compton Spectrometer and Imager (COSI) is a wide-FOV telescope designed to survey the COSI has a large science portfolio that includes all-sky gamma-ray imaging for mapping The heart of COSI is a stacked Fe is almost exclusively released into the interstellar medium (ISM) during core collapse super- gamma-ray sky at 0.2–5 MeV, performing high-resolutionmeasurements. spectroscopy, imaging, COSI will and map polarization the Galactic positronconcentration annihilation emission, of revealing the this mysterious emissiondetail. near the Galactic COSI center willcreation and elucidate and the evolution Galactic the of bulge role the in of elements unprecedented by supernovae mapping (SNe) tracer and elements. other COSI stellar will populations image in the The Compton Spectrometer and Imager 1. Overview unprecedented sensitivity, perform the first mapping of nucleosynthesis has occurred over60 the past millions of years and wherenovae it (CCSNe), is occurring now. While 2. COSI Science Objectives electron-positron annihilation emission, radioactiveThe decay long lines, radioactive decay and time Galactic scales diffuse of emission. remnants through complete sky coverage over a day (see1). Figure array of germanium cross-strip detec- tors, which providehigh resolution high spectroscopy, and efficiency, pre- cise 3D positioning of photon interac- tions. As COSIscope, is 3D a positioning Comptoncarry is tele- required out to thestruction. Compton event We recon- accomplishthe this versatile MEGAlib using software pack- age [30]. The detectorsa are housed cryostat in and cooled to are shielded on five sides, reducing the background and defining the FOV. The COSI shields are activeextending scintillators, COSI’s FOV forof detection GRBs and other sources ofray gamma- flares. COSI willmode, be alternately in pointing low-Earth orbit and will spend most of the mission time in a survey will also study compact objects bothproviding in novel measurements our of Galaxy polarization and as well AGN as as detailedFOV well spectra and as and localization light gamma-ray curves. capabilities bursts make (GRBs), The COSI itgravitational powerful for wave and searches high-energy of neutrino electromagnetic counterparts detections. to PoS(ICRC2021)652 ) f Fe (1.173 and 60 John A. Tomsick Al (1.809 MeV line) and 26 Ti (1.157 MeV as well as 68 and 78 keV lines in 3 44 The COSI narrow line sensitivity for point sources (3 . This raises questions about the origin of the positrons ◦ 9 > compared with COMPTEL and INTEGRAL/SPI. Figure 2: Al, 10,000 CCSNe. 26 Co (0.847 and 1.238 MeV) decays so rapidly (half-life: 77 days) that ∼ 56 The production of positrons and their annihilation in the Galactic ISM is one of the pioneering The MeV bandpass includes nuclear emission lines that probe different physical processes in , while Siegert et al.]) ([21 obtain ◦ Ti produced in SNe decays quickly by comparison, showing where recent supernova events have 3 1.333 MeV lines), predominantly produced in SNe,formation provide history, information about integrated the over galaxy-wide the star these past energies million trace years. the last To first order, images of the Galaxy at topics of gamma-ray astronomy.0.511 MeV Despite line five from decades of theINTEGRAL/SPI’s study inner imaging since led Galaxy to the [9, a initial14],a map detection of the bright of the origin bulge the annihilation of emission andany from these definitive fainter the positrons information Galaxy disk about remains that [3]. sub-structure uncertain. shows detected, in and the the origin The of emission. the angular bright bulgemeasured No emission resolution by is individual INTEGRAL/SPI unclear. of sources is The scale the also have height uncertain, been of∼ SPI the with disk Skinner map emission et does al. ([22]) not finding provide an rms height of our Galaxy and beyond. Long-lived isotopes such as remnants.which The decay produces of gamma-ray a andthe a 1.809 MeV prominent positron, knownpositrons through source is nucleosynthesis, of but observations of the 0.511 MeV positron annihilation line indicate that one orknown more sources of additional positronsinate un- dom- their production.comparing the full Galaxy It maps of positron is annihilation by and radioac- tive isotopes from nucleosynthesis that we can understandof the the origin “extra” positrons.sensitivity The that high COSI providesthese for emission lines compared to earlier measurements makes this goal possible (see2.12). Figure Probing the Origin of Galactic Positrons as well as how far they propagate.the number Even more of fundamentally, positrons the in uncertain thethe scale disk 0.511 height MeV is means line uncertain that is by the aof strongest factor persistent this of gamma-ray anti-matter signal, more component gaps of than remain our three. in Milky Thus, our Way [11]. even understanding though 2.2 Revealing Element Formation the hard X-ray range), with a half-lifelast of few 60 hundred years, years, traces and young Galactic SNe which occurred in the The Compton Spectrometer and Imager 44 occurred in the last several hundred years and allowing for detailed studies of individual supernova PoS(ICRC2021)652 , and 14% of 13 . John A. Tomsick 0 = I 25% of the sky to fulfill an 50%. > < 4 Polarization measurements provide unique diagnostics for determining emission mechanisms A Compton telescope like COSI has intrinsic polarization sensitivity because the gamma-rays COSI significantly contributes to multimessenger astrophysics with its capability to find coun- For gravitational waves from BNS mergers like GW170817/GRB170817A [1,7], COSI is able A COSI launch in 2025 would mean that it is observing when A+ generation gravitational 15-20 short GRBs in two years. While the COSI shields will only provide rough localizations, they and source geometries (e.g., magneticglimpse field, into accretion the disk, potential and for jet), whatof we but can 19% current learn. results [19, In give28], X-rays, just theX-ray but a polarimeter Crab most nebula like the was sources detected upcoming show at Imaging upperthe a X-ray Polarimetry COSI level limits bandpass, Explorer well much [27]. higher below Above polarization 0.2 this,the levels MeV, in have requiring accreting been black a measured hole for very Cygnus the X-1 sensitive Crab [10, [5,6]]. 13 and for preferentially scatter in a direction perpendicular toCOSI their to electric polarization field. and the Thus, fact with thatbe the COSI expected sensitivity observes to of in be a bandpass high where forfor the certain many polarization types sources. level of can In sources, addition COSI to isCyg pulsars likely X-1), to (like COSI obtain the will polarization Crab) be and detections ableFOV accreting allows to stellar for measure mass detection black polarization of holes large for (like numbers severalbeen of AGNs reported GRBs, (like [18]. for Cen which In A), polarization a and levelspolarization 2-year above its measurement 50% mission, wide with have COSI a will minimum see detectable at polarization least of 40 GRBs bright enough to obtain a terparts to multimessenger sources.binary This neutron includes star counterparts (BNS) mergers to as gravitational well wave as events neutrino from detections [8]. to detect and localize the BNShave by large FOVs finding but the poor associated localization short capabilities,localization and GRB. coded capabilities Scintillator-based aperture but instruments smaller mask FOVs instruments than have good COSI.capability With for Compton sub-degree imaging, localizations COSI with combines instantaneous the coverage of wave detectors are planned to beis in 620 operation. Mpc (see In the Tabledistribution A+ 4 averaged over era, the in the full-sky. [4]) A joint distance for BNS-GRB of detection the 620 Mpc range three corresponds to LIGO interferometers, which takes a near face-on The Compton Spectrometer and Imager it is currently only seen byamount following and up distribution SNe of in these nearbyindependent galaxies. radioactive and isotopes more These direct created lines view in allow of us the Galactic to chemical underlying trace evolution SNe [24]. the giving us2.3 an Insight into Extreme Environments with Polarization 2.4 Multimessenger Astrophysics important need for gamma-ray capabilities to∼ detect and localize GRBs.double We the estimate COSI detection FOV of and allowgravitational comparison wave signal of from the BNS arrival merger. timeis While of uncertain, the short it cause GRB may of to relate the to the 1.7or the sec arrival the time delay of time for of the internal for GRB170817A the shocks to merging form NSs in to the collapse jet, into the a shock black breakout hole. time, short GRBs are within that redshiftdetections [4]. of 4.2-5.6 Thus, events we during would predict the joint 2 COSI year COSI and prime gravitational wave mission. PoS(ICRC2021)652 John A. Tomsick with respect to its initial \ that induces the signal measured 1  Schematic of interactions for a single ) and the energies of the incident and scattered 2 A Figure 3: gamma-ray in a Compton telescope. 5 to 1 A 46% [16], and < , creating a recoil electron of energy 1 A undergoes a Compton scatter at a polar angle W  COSI employs a novel Compton telescope design using a compact array of cross-strip germa- We have developed the COSI instrument The data from the 2016 flight have also been vital for completing the software pipeline for the COSI provides major improvements in capabilities over previous MeV instruments. Compared The COSI instrument utilizes Compton imaging of gamma-ray photons [2, 26]. An incoming nium detectors (GeDs) to resolve individualresolution. gamma-ray interactions No other with technology high thus spectral farcapability and tested in spatial exceeds this COSI’s energy spectral range. resolution The and COSI polarization cooled array by of a 16 CryoTel CT GeDs mechanical is cryocooler. housed in Theintegrated a GeDs into common are vacuum the read cryostat full out data by a acquisitionsides custom system. and ASIC, bottom which An is to active veto BGO events shield from encloses outside the the cryostat FOV. The on COSI the instrument is shown in4. Figure gamma-rays. through NASA’s Astrophysics ResearchAnalysis and (APRA) program,altitude including balloon flights high- inand 2016, 2005, providing 2009, a very 2014, importantconcept. proof of During aCOSI 46-day imaging, flight spectroscopy, polarization, in and 2016,real-time the localization capabilities were demon- strated. We were able to detect, localize, and re- port GRB 160530A in real time [25].sis An analy- of the GRB 160530A data resultedper in limit an on up- the polarization of COSI imaging technique. Wesuch have as demonstrated the the 0.511 modeling MeV emission ofpulsar from extended as the source a Galactic distributions, point bulge [20], sourcethe image, and for which also testing can used be the used the technique formeasuring Crab testing [31]. fluxes, nebula between extents, physically-motivated and spatial and sky The significances distributions of software and the allows emission for that model is detected. fitting of to COSI-APRA, the number ofposition detectors resolution is due increased to from the 12 stripinto to pitch a 16, being and decreased similar they from improvement have 2 mm 2 in to times angular 1.16 better mm, resolution. which translates Also, being above the atmosphere provides direction at the position in the detector (seeinteractions, which3). Figure are also measured. The Thethe scatter Compton scattered direction formula (measured photon relates direction the from then initial photon undergoes direction a to series of one or more new techniques were developed for polarization studies [17] and for calibrating[15, the].29 instrument The detection of the 0.511sion MeV and emis- information about the linehave shape also and used spatial calibration extent measurements is to reported benchmark in the Kierans detector et effects al. engine ([12]). [23]. We photon of energy The Compton Spectrometer and Imager 3. COSI Instrument PoS(ICRC2021)652 . The BGO 3 Al emission 26 cm 5 . John A. Tomsick 1 × 8 × 8 6 25% of the sky is to detect enough GRBs to achieve > Ti-emitting SN remnants, and the ability to isolate 44 . 3 cm 20 × 46 × 42 Cutaway view of the COSI instrument. Each germanium detector is Ti line, which provides information about SN explosions. The required sensitivities and 44 To improve the user-friendliness of the COSI analysis software and to prepare the high-energy Table 1 shows a sample of the requirements for COSI to achieve the science goals outlined Fe, a sensitive search for young from individual massive star clusters.to While be the large covered, FOV the requirement main allows driver for for the covering full Galaxy community for analyzing COSI data,For this the project, COSI the group COSI teamfull is will COSI carrying imaging publicly release response, out a and a documentation set Data of of our astrophysical Challenge source python-based project. simulations, analysis software the (COSIpy). COSI’s polarization and short GRB localization goals. 5. Data Challenge Project angular resolution allow for COSIbulge to 0.511 MeV distinguish emission between models.60 different physically-motivated Also, Galactic these requirements provide the first images of Galactic above. A key requirement for COSI is havingemission excellent over spectral the resolution entire for Galaxy. making images The of spectralin line resolution narrow is energy important bands for being around able theresolution to is lines make used of images to interest measure to line minimizeas profiles background. the in order In to addition, study spectral the width of the 0.511 MeV line as well shield box is enormous improvements. Theby simple 3-4 removal times, of depending on atmosphericcompared energy, to attenuation and much improves being larger sensitivity above currentmagnitude the improvement and in atmosphere previous narrow reduces line satellite background. sensitivity missions, (see COSI2). Figure Even will provide an order4. of COSI Requirements Figure 4: The Compton Spectrometer and Imager PoS(ICRC2021)652 6 6 − − 10 10 FWHM × × ◦ 0 0 . . 3 5 John A. Tomsick c . 1 − s . 2 2 − − (1.809 MeV) 0 . 1 − s 2 − ParameterFOVSpectral Resolution (1.157 MeV)Angular Resolution (1.809 MeV) 3.9 keV rms Line Sensitivity 2.0 GRB polarization fluence limit Requirement 25% sky 7 5 10 COSI Requirements − − 10 10 FWHM × × ◦ 0 4 . . 1 1 Table 1: b (0.511 MeV) a narrow line sensitivity in 2-years of survey observations in units of photons cm f COSI will open up the MeV energy band to explore the science of positrons, nucleosynthesis, Detection limit for 2-years of survey observations in units of erg cm 3 For 50% minimum detectable polarization. The fluence limit is in units of erg cm c b a Flux limit for polarization ParameterEnergy RangeSpectral Resolution (0.511 MeV)Angular Resolution (0.511 MeV) 2.6 keV rms Line Sensitivity 3.8 Requirement 0.2-3 MeV polarization studies of GRBs and accretinglarge black FOV holes, and and observing multimessenger strategy, it astrophysics. will WithThe cover its the COSI entire team sky will in be theprovided starting 0.2-5 on MeV the bandpass the Data every COSI day. Challenge in websiteenter the (http://cosi.ssl.berkeley.edu). Phase latter B If part in COSI of January is 2021, 2022 selected and and launch for updates in flight, will late-2025. it be will References [1] Abbott, B. P., Abbott, R., Abbott, T. D.,[2] et al.Boggs, 2017, S. Physical E., Review Letters, & 119, Jean, 161101 P. 2000, A&AS,[3] 145, 311 Bouchet, L., Roques, J. P., & Jourdain, E.[4] 2010, ApJ,Burns, 720, E., 1772 2020, Living Reviews in Relativity, 23,[5] 4 Dean, A. J., Clark, D. J., Stephen,[6] J. B.,Forot, et M., al. Laurent, 2008, P., Science, Grenier, 321, I. 1183 A., Gouiffès,[7] C., &Goldstein, Lebrun, A., F. Veres, 2008, P., Burns, ApJ, E., 688, et L29 al.[8] 2017, ApJ,IceCube 848, Collaboration, L14 Aartsen, M. G., Ackermann, M.,[9] et al.Johnson, 2018, W. Science, N., 361, Harnden, 147 F. R., & Haymes,[10] R. C.Jourdain, 1972, E., ApJ, Roques, 172, J. L1 P., Chauvin, M., &[11] Clark, D.Kierans, J. C., 2012, Beacom, ApJ, J. 761, F., 27 Boggs, S., et al. 2019, in BAAS, Vol. 51, 256 The Compton Spectrometer and Imager Documentation and “cookbook” examples willCOSI-APRA balloon be data provided will to be releaseddata. the to participants. allow people to In apply addition, what they the have learned to real 6. Conclusions and Schedule PoS(ICRC2021)652 John A. Tomsick 8 INTEGRAL Workshop: A Synergistic View of the High-Energy Sky”, 10 Physics Research A, 946, 162643 2016: Ultraviolet to Gamma Ray, Vol. 9905, SPIE Proceedings, 990517 220, L117 tion 2018: Ultraviolet toEngineers Gamma (SPIE) Conference Ray, Series, Vol. 106992K 10699, Society of Photo-Optical Instrumentation The Compton Spectrometer and Imager [12] Kierans, C. A., Boggs, S. E., Zoglauer,[13] A., etLaurent, al. P., 2020, Rodriguez, ApJ, J., 895, Wilms, 44 J., et al.[14] 2011, Science,Leventhal, 332, M., 438 MacCallum, C. J., & Stang, P.[15] D. 1978,Lowell, ApJ, A., 225, 2017, L11 Ph.D. thesis, University of[16] California, Berkeley Lowell, A. W., Boggs, S. E., Chiu, C.[17] L., etLowell, al. A. 2017a, W., Boggs, ApJ, S. 848, E., 120 Chiu, C.[18] L., etMcConnell, al. M., 2017b, Ajello, ApJ, M., 848, Baring, 119 M., et[19] al. 2019,Novick, R., in Weisskopf, BAAS, M. Vol. 51, C., 100 Berthelsdorf, R., Linke,[20] R., &Siegert, Wolff, T., R. Boggs, S. S. 1972, E., ApJ, Tomsick, 174, J. L1 A.,[21] et al.Siegert, 2020, T., ApJ, Diehl, 897, R., 45 Khachatryan, G., et al.[22] 2016, A&A,Skinner, 586, G., A84 Diehl, R., Zhang, X., Bouchet, L., &[23] Jean,Sleator, P. C. 2014, C., Zoglauer, in A., Lowell, Proceedings A. of W., et “10th al. 2019, Nuclear Instruments[24] andTimmes, Methods F., in Fryer, C., Timmes, F., et al.[25] 2019, inTomsick, J. BAAS, A., Vol. 51, 2016, GRB 2 Coordinates Network, 19473,[26] 1 von Ballmoos, P., Diehl, R., & Schoenfelder, V.[27] 1989, A&A,Weisskopf, 221, M. C., 396 Ramsey, B., O’Dell, S., et al. 2016, in Space Telescopes and Instrumentation [28] Weisskopf, M. C., Silver, E. H., Kestenbaum, H. L., Long, K.[29] S.,Yang, & C. Novick, Y., R. Lowell, 1978, A., ApJ, Zoglauer, A., et al. 2018, in Space[30] Telescopes andZoglauer, Instrumenta- A., Andritschke, R., & Schopper, F. 2006,[31] New AstronomyZoglauer, Reviews, A., 50, Siegert, 629 T., Lowell, A., et al. 2021, arXiv e-prints, arXiv:2102.13158 PoS(ICRC2021)652 , , , 4 9 12 1 Institut , Dieter 5 4 Clemson 6 , Terri Brandt 3 , Hannah Gulick , Fabrizio Tavecchio 1 John A. Tomsick 5 , Kazuhiro Nakazawa 11 , Carolyn Kierans 4 Kavli IPMU, The University Center for Astrophysics and 2 , Clio Sleator 11 3 , Julien Malzac 1 , Alan Smale 1 , Jacqueline Beechert 1 , Bernard Phlips , Tadayuki Takahashi 3 10 Los Alamos National Laboratory, New Mexico, USA. U.S. Naval Research Laboratory, 4555 Overlook Ave., 8 3 , Hadar Lazar 1 , Pascal Saint-Hilaire , Lee Mitchell 8 3 , Juan Martinez Oliveros 5 9 , Hsiang-Kuang Chang 9 , Eric Wulf 1 , Chris Fryer 7 , Alexander Lowell 13 Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Campus 13 , Peter von Ballmoos 5 , Eric Burns 6 Insitute of Astronomy, National Tsing Hua University, Taiwan. 10 , Giancarlo Ghirlanda , Andreas Zoglauer 9 2 , NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA. , Thomas Siegert 1 4 Louisiana State University, Louisiana, USA. 11 7 , Pierre Jean 2 , 1 , Marco Ajello 6 , Tom Melia Nagoya Univeristy, Japan. 11 12 , Andrea Bulgarelli , Steven E. Boggs 9 1 , Jarred Roberts 4 , Mark Leising 6 Istituto Nazionale di Astrofisica, Italy. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450, USA. The Compton Spectrometer and Imager Full Authors List: COSI Collaboration John A. Tomsick Albert Shih Hartmann Valentina Fioretti Hubland Nord, Emil-Fischer-Str. 31, 97074, Würzburg, Germany. Shigeki Matsumoto de Recherche en Astrophysique etUniversity, South Planétologie, Carolina, 9, USA. avenue9 du Colonel Roche BP 44346of 31028 Tokyo, Toulouse Japan. Cedex 4, France 1 Space Sciences, UC San Diego, 9500SW Gilman Washington, DC Drive, La 20375, Jolla USA. CA 92093, USA.