PoS(HEASA 2016)001 . AstroSAT http://pos.sissa.it/ , and CALET , MAXI , IPN , NuSTAR , INTEGRAL , AGILE , satellites continue to chase gamma-ray bursts (GRBs) and make ground- Fermi , Fermi Spitzer , and ∗ Swift Chandra , [email protected] [email protected] Speaker. breaking discoveries. The resulting sciencecoincident has event been searches greatly from a enhanced variety by of follow-upof observatories, studies the including RAPTOR, Sky, and Watcher, MASTER, REM, iPTF, Pi GROND, GTC,Telescope, RATIR, DCT, KAIT, Asiago, NOT, Nanshan, Gemini, Liverpool Robotic Magellan,GMRT, CARMA, Keck, LOFAR, VLT, HAWC, VLA, VERITAS, ACTA,HST MAGIC, ALMA, HESS, AMI, IceCube, WSRT, ANTARES, LIGO, NASA’s These observatories have added tothe our short-lived knowledge reverse-shock of which the has been early-time seenThe behavior now emphasis of in on GRBs, a longer small such handful term as with of optical the the observations, brightest prospects days bursts. in to a weeksgood few after localizations years for the for compact burst, multiple object has mergers, active andemission increased gravitational the if wave potential one observatories for of providing seeing the the objects isotropic is kilonova a neutron star. ∗ Copyright owned by the author(s) under the terms of the Creative Commons c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). John K. Cannizzo CRESST/Joint Center for Astrophysics, Univ. of21250, Maryland, USA Baltimore County, Baltimore, MD E-mail: Neil Gehrels Astroparticle Physics Division, NASA/Goddard Space FlightE-mail: Center, Greenbelt, MD 20771, USA GRBs in the Era of Rapid Response Telescopes 4th Annual Conference on High Energy25-27 Astrophysics August, in 2016 Southern Africa Cape Town, South Africa PoS(HEASA 2016)001 2 c

M 30 ms 6 FOV, . ∼ > ∼ 0 23 Neil Gehrels × of CdZnTe de- 6 . 2 0 100 s. Since this bandpass is . The actual energy involved 2 − c 1 .

0 M ∼ is the bulk Lorentz factor of the flow. Γ 350 keV) imager with 0.5 m effective area at 1.5 keV, 23 300. GRBs are thought to result from either 2 − − since the reverse shock propagates into the jet, Γ 10 1 ∼ ∼ effective area at 20 keV including mask occultation) 2 stars in the universe. The total energy released is 22 2400 cm -ray emission which lasts 10 γ ∼ ∼ 10 keV energy range, 120 cm − 2 . compared to the forward shock, where minutes, days, and even months post-burst. For a small handful of GRBs, one sees 2 Γ − erg). GRBs are the second most powerful transients, with isotropic equivalent energy – A Time Domain Observatory 54 (Gehrels et al. 2004) carries three instruments, a wide-field Burst Alert Telescope (BAT; 100 times that of all the 10 − × Swift 8 The most powerful transient events in the universe observed to date are merging black hole Rapid GRB follow-up observations are crucial for detecting early optical afterglow. The fire- These basic physical considerations demonstrate the necessity of having both space-based Swift . 10 1 ray detectors with localization capability. GRB counterparts, “afterglows”, can appear later in ∼ − = tectors (32,000 individual sensors; the catastrophic core-collapse of massive stars,one neutron or star, from i.e., compact NS-NS object orGRBs mergers BH-NS are involving (Piran found at & via least their Fan “prompt” 2007; Gehrels, Ramirez-Ruiz, & Fox 2009). and a 1.4 sr half-coded fieldtelescope of with view a (FOV). 0 XRT is a Wolter 1 grazing incidence, imaging X-ray binaries (Abbott et al. 2016ab) for which the luminosity in gravitational waves in the final optical emission at the same time as the prompt emission. ball model accounts for the afterglowthe peak circumstellar as environment of being the either GRB, due orthrough a to reverse the a shock GRB forward moving backwards shock jet in passing plasma the through emission ejecta itself frame lasts (Zhang only & a Kobayashi short 2005; timeshock due Piran propagates to & the backwards Fan short from 2007). crossing the time Reverseby contact of shock a discontinuity, the factor the GRB ejecta. of emission Since peaks the at reverse energies lower missions and ground-based rapidoptical response afterglow, and observatories thereby in to gainshocks. order potential to insight into study the effectively physics the of the early forward1.1 and reverse Space Observatories 1.1.1 Barthelmy et al. 2005) thatfield detects X-Ray Telescope GRBs (XRT; Burrows and et al. positions 2005),et them and al. to the 2005). UV-Optical arcminute BAT Telescope is (UVOT; accuracy, Roming a the coded aperture narrow- hard X-ray (15 GRBs/Rapid Response Telescopes 1. Catching GRBs in the Act is ( (i.e., estimated from beamed flux)is in less some by cases the approaching reciprocal of the beaming factor blocked by Earth’s atmosphere, these discoveriesγ must be made by space-basedthe missions X-ray, carrying optical, and radionearly bandpasses always after seen; the optical prompt and radio emissionof afterglows time has are scales faded. rarer. Afterglow X-ray can afterglow encompass is a wide range However, the luminosity is greater bywhich a has a factor higher density ofverse the shock seed emission electrons can responsible reveal properties forof of the the the synchrotron peak jet, emission. fluxes such The of as re- the baryonestimate spectral loading. of components the In associated jet addition, with magnetization the forward (Harrison ratio and & reverse Kobayashi shocks 2013; gives Laskar an et al. 2013). PoS(HEASA 2016)001 techni- = Neil Gehrels at 350 nm, and 00 9 . 3 s. Each wide-field < mission was built by an international FWHM), and sensitivity of approxi- 00 FOV, PSF FWHM of 1 (7 0 Swift 00 17 × 0 s. The 2 3 was launched into low-Earth orbit in June 2008. Fermi s. The UVOT is a modified Ritchey-Chrétien reflector with 4 FOV; thus the sky can be covered in eleven pointings. Each ◦ 38 in 10 1 × − ◦ s 2 − 300 GeV (Atwood et al. 2009) and the Gamma-Ray Burst Monitor (GBM) 650 nm wavelength range, 17 > ∼ GRBs and transients. of silicon detectors. It is a pair conversion telescope with silicon detector − 2 magnitude in white light in 10 erg cm Swift rd 14 − – A High Energy Observatory 10 has two primary high-energy detectors: the Large Area Telescope (LAT) which operates catches about two GRBs in a week, and carries out about three ToO observations a day. × Fermi RAPTOR is a suite of telescopes designed to detect and track transient objects, including Here are descriptions of some of the rapid-response optical telescopes that perform follow-up RAPTOR participates in the Los Alamos Thinking Telescope Project, an effort to develop Fermi The newest telescopes are RAPTOR-K and RAPTOR-T, which began operation in 2008. Swift gamma-ray bursts. It was builtrobotic by observatories, a designated team RAPTOR A, at B, Losindividual S, Alamos telescopes P, are K, led controlled and by by T, Tom all a VestrandRAPTORs located central and A, near computer consists B, Los system. S, of Alamos. and The six P The older eachsix RAPTOR include telescopes, both are a mounted wide-field on telescope and platforms a capable narrow-field telescope. of All swiveling to any sky location in 1.2.1 RAPTOR (Rapid Telescopes for Optical Response) observations of hardware and software with the goal ofRAPTOR managing logistics led of to transient SkyDOT, object the detection. Sky In Database addition, for Objects in Time-Domain. between 20 MeV and which operates between 8 keV and 40consisting MeV (Meegan of et al. 77 2009). m Thetracker LAT is and a cesium 3000 kg iodide instrument calorimeter.public immediately. The LAT The scans GBM the isand full a two sky scintillator-based bismuth germanate every instrument detectors. 3 with 12 hr; sodium all iodide data detectors are1.2 made Follow-up Telescopes telescope has a nominal 38 color) has four co-aligned 0.4 mphotometry telescopes during with four a filters. GRB, It and cancircumstellar thereby therefore environment. constrain provide its time-resolved distance as well as the GRB’s dynamics and RAPTOR-K has 16 lenses and can view the entire sky every 5 min. RAPTOR-T (T 30 cm aperture, 170 1.1.2 telescope is two telescopes, enabling stereoscopicRAPTOR vision. takes Each two telescope consecutive also 30 has s zoomthe exposures capability. through resulting its digital two wide-field images telescopes whilezooms and in in analyzes for monitoring a mode. closer look with If the it two sees narrow-field telescopes. an interesting event, RAPTOR GRBs/Rapid Response Telescopes point spread function (PSF) half-powermately diameter 2 of 18 sensitivity of 23 team from the US, UK,the and development Italy, and with operations. contributions alsoSpace After from Center five Germany, on years Japan, 20 of November and development 2004. Denmark it Full in normal was operations launched commenced from on Kennedy 5 April 2005. PoS(HEASA 2016)001 , th 1 Neil Gehrels erg. A detailed examination of the 52 10 ' iso E 34, it had the largest GRB fluence ever recorded. . 3 0 = z erg, GRB130427A had 48 10 ∼ values of Best-fit with a reverse/forward shock model to the optical light curve of GRB afterglow 130427A iso E The scientific highlight for RAPTOR has been GRB130427A which was seen peaking at 7 Figure 1: (Vestrand et al. 2014). Three episodesthe of early ejecta optical emission and (up energy injection to are few kiloseconds), needed and to the explain late the optical optical emission flash, (after a few kiloseconds). GRBs/Rapid Response Telescopes mag (Vestrand et al. 2014). At a redshift of light curves in different bandsfrom allows Vestrand et one al. to 2014). constrain the forward and reverse shocks (Figure The burst was accompanied bytypical SN 2013cq (Xu et al. 2013). In contrast to other GRB/SNe with PoS(HEASA 2016)001 . Swift 1 filters − I s , ◦ 10 s. The R 10 , Neil Gehrels − ∼ V 1 ∼ /BAT. Swift filters; ROSS has standard FOV, and an f/2.2 focal length of 1.32 m. 0 0 9 K 13 mag with time resolution 0.1 s. × ∼ 0 − , and 4 H , J , 0 z resolution, a 9 00 16 . 8 steradian), similar (by design) to that of . 1 ∼ 2300 nm wavelength range. Its small size facilitates a fast slew rate − FOV. Its optimized time resolution is ◦ 450 32 = × ◦ λ Watcher is located at Boyden Observatory in South Africa; it saw first light in 2006. Its primary A sequence of images of a given source is turned into a calibrated light curve via the walapi REM is an autonomous telescope at La Silla Observatory whose objective is to catch GRB It was built in 2002-2003 and saw first light in September 25, 2003. The telescope is a 0.6 m Pi of the Sky is a system of wide FOV automated telescopes which operates autonomously. It The telescope has REMIR, an imaging IR camera, and ROSS, a visible imager and a slitless The observing procedure is completely robotic and the nightly schedule is optimized for the A wide FOV camera parallel to the REM telescope, TORTORA (Telescopio Ottimizzato per It has scientific objective is to study the optical promptconsists and of early a afterglow 0.4 emission from m GRBs. f/14.25filter-wheel Watcher Cassegrain with primary BVRI mirror. filters. It has The ancontrolled software Andor by runs EMCCD the on camera open two and source Linux Optec RTS2 machines, software and package. the entire system is pipeline which determines the statistical zero-pointis for being each image replaced using by all aondary stars standards in faster within the Python an field. watcher-pipeline image This for thatbrightnesses, calibration. uses along The several APASS with catalogue of the is thetarget’s now USNO-B1 magnitude most used are catalogue. for suitable adjusted reference sec- in Parameters real-timeof used based the on in current source, the seeing, i.e., image determinationdetectability. whether quality, of and it the the is nature a known bright source1.2.3 or Rapid a Eye Mount faint telescope GRB (REM) afterglow at the limit of afterglows. It is triggered automatically by GCN alerts from high-energy satellites such as Ritchey-Chrétien reflector with 1 GRBs/Rapid Response Telescopes 1.2.2 Watcher Robotic Telescope and rapidly slews to the localization. It(INAF). is operated by the Italian National Institute for Astrophysics system was successfully tested withto a 2009 prototype and at moved to Las San Campanas Pedrounit Observatory de of (Chile) Atacama the from Observatory in final 2004 March Pi 2011.El of In the Arenosillo October Sky Test 2010 detector the Centre first system, ininstalled with Spain. together four with CCD In the cameras, July first was 20136000 installed one, square three at on degrees more the a (or INTA units new platform (12 in CCD INTA, cameras extending total) sky were coverage to about monitors a large fraction of the sky to a depth of 12 1.2.4 Pi of the Sky spectrograph. A dichroic locatedsame before FOV the at telescope the focus same enables time. both REMIR cameras has to observe the observation of scheduled targets butcally it REM is can immediately observe overdriven the by new GRB target after (or 30 other) seconds alerts. from notification. la Typi- Ricerca dei Transienti Ottici RApidi),and was 24 installed in 2006. TORTORA has a 0.12 m objective and a slitless Amici prism. PoS(HEASA 2016)001 ; 1 − 2) . − 1 mag GCN 018 = th . 0 d / ∼ 4112 pixel f FOV. IO:O 2048 pixel Swift Neil Gehrels 3 FOV. IO:I 0 m arcsec . × 0 × µ 6 10 × × 0 3 1024 active pixels, . ), and narrow-band 0 V × and mag; it rises to 13.5 B th along the diagonal of the CCD ◦ 85 mm Canon lenses ( GCN alert. Pi of the Sky has four = f ), Bessell ( 0 z Swift , 0 i , 0 r , 0 g 5 , 0 . The autoguider permits closed loop tracking and 10 mag. Photometric accuracy is improved further u 1 − − IO:O does the optical imaging. It is a 4096 m pixel size, 0.15 arcsec pixel scale, and 10 m pixel size, 0.18 arcsec pixel scale and 6 µ m arcsec m size, peak quantum efficiency 95%, operating temperature µ µ µ 15 IO:I does the NIR imaging. It consists of a 2048 18 13 × × × FOV with one mount. m ◦ µ 38 ray emission, or prior to it. The full Pi of the Sky FOV constantly follows × FOV, or (ii) individual cameras to deflect 13 , 13 − ◦ 1 ◦ γ in real time such that they both “see” the same patch of sky at all times, thereby − 20 FOV. The limiting magnitude for a single frame is 12 ◦ × Swift ◦ 20 rest wavelength 656.28 nm, and redshifted to 663.4, 670.5, 675.5, and 682.2 nm. × α ◦ C, and pixel readout rate 1 MHz. Translational tracking errors are corrected, rotational errors Located at the Roque de los Muchachos Observatory on La Palma, the 2m Liverpool Telescope LRT has several instruments which areOptical relevant Wide for Field GRB Camera studies: (IO:O): The scientific highlight of Pi of the Sky thus far has been GRB 080319B. At 6:12:49 UT By selecting only high quality measurements, an average photometry uncertainty The standard model for robotic telescope operations is to receive GCN alerts which then relies Near-IR Camera (IO:I): ◦ 40 024 mag has been achieved for stars of 7 . is a fully robotic Ritchey-Chrétien telescope.the The secondary f/3 primary mirror mirror is has 0.62 a 0.45 m m in central bore diameter. and The prime focus image scale is 29.1 alert arrived indicating the discovery ofreached the 5.3 extremely mag, luminous which GRB. was Atfrom impressive its considering peak Pi it the of optical lay light the atallowed a Sky, detailed redshift constraints combined to of with be 0.937. placed panchromatic onsection The the 4 observations optical physics below). data from of GRB a 080319B (Racusin variety et of al. 2008, observatories, 1.2.5 see Liverpool Robotic Telescope (LRT) the Cassegrain image scale iscorrects 97 tracking errors via guide0.22 star arcsec monitoring. pixel The autoguider− has 1024 are not. e2v CCD 231 detector with 15 utilizes a 12 position filter wheel with Sloan ( on March 19th 2008 Pi of the Sky detected a new object, and a few seconds later a via a dedicated color correctionfor algorithm. most When of performing the observations data), without measurements any are normalized filter to (i.e., reference stars measured in V. custom designed CCD cameras per mount.with Each 20 camera has ship, enabling a 38 0 the FOV of eliminating any delay time due to repointing based on a on rapid repointing to prompt opticalsame afterglow. time This as method the does not allow for a detection at the GRBs/Rapid Response Telescopes for a frame stacked fromexcept for 20 an exposures. IR-cut filter Beforethe in 2009 cameras order all has to observations had minimize a were thefull Bessel-Johnson made sky R-band suite in background. filter consists white in Starting of light, order in 16per to May cameras mount). facilitate 2009 placed absolute The one on calibration. specially of four designed The The equatorial specially mount camera designed allows deflecting equatorial the mechanism mounts cameras allows (4 tocommon either operate cameras (i) 20 in all two cameras modes. to point at the same object, with a filters, H Hawaii 2RG detector with 18 PoS(HEASA 2016)001 , 00 00 3 . . Median 00 RMS. With Neil Gehrels 2 800 nm and 00 GRBs. It can ∼ FOV and 0 − z 0 15 − 350 tons, and has 10 ∼ 400 . ∼ × = 0 H λ ) on the 1.5 m Johnson and H SPRAT is a low resolution , and a slit width of 1.8 00 J plus seven others, while C1 , and ugr J , Y , z RMS. Offset precision is , r 00 350. , mag; SkyCam-T, a medium FOV camera 1 i = ∼ th 6 m. Each telescope weighs δλ ∼ µ / mag; SkyCam-Z, a zoomed FOV camera with a 6 λ th = 14 R , while C3 uses fixed MKO − Y 13 and ∼ 300 nm to 20 Z = . 00 λ 1 mag. pixel size. For filters, C0 uses SDSS ∼ 30 s of a GCN alert. The nominal pointing error is th 00 ∼ is 18 32 . ∼ FOV sensitive to . Detectors C2 and C3 are HAWAII-2RG detectors with 10 i ◦ irzYJH The system consists of three cameras: SkyCam-A, an all sky camera on a fixed 2028 pixel format. The first two, C0 and C1, are Fairchild 3041 CCD detectors with 9 FOV. It has a dispersion 0.46 nm/pixel, a slit length of 95 4 FOV and 0 . . 0 0 × 1 5 FOV sensitive to The VLT is operated by ESO at Paranal Observatory, Chile. It consists of four individual The wavelength range is Three dichroics divide the light from the telescope into four channels, C0 through C3, all with SPectrograph for the Rapid Acquisition of Transients (SPRAT): SkyCam: The telescope’s robotic control system (RCS) accepts observation requests from professional The LRT is one of the largest robotic telescopes. It was built by Telescope Technologies Ltd, a The RATIR camera is a 6 color imaging system ( × × ◦ 4 5 1 . . 0 0 active optics: 150 supportsmirror on via the actuators controlled back by of computers. each primary control the shape of the 0.177 m thick telescopes. They are usually used separatelyresolution. but Each can telescope be is employed in ofprimary unison Ritchey-Chrétien mirror, to Cassegrain and obtain design a high with angular 1.1 atwo m 22 Be instruments ton, secondary 8.2 at mirror. m the Zerodur A f/15primary flat mirror Nasmyth tertiary central foci mirror hole on diverts to the eithersend a light side, the third to light or instrument one via tilts at of tunnels aside thefoci to is to Cassegrain around the focus. allow 27 central light arcminutes Additional VLTI diameter. through mirrors beam-combiners. the can The maximum FOV at Nasmyth telescope at San Pedroas Mártir the Observatory science in imager. Mexico. Ittypically The is observe dedicated telescope within to is the automated follow-up with and RATIR identification of high 1.2.7 VLT X-shooter a 2048 5 a sufficient density of brightimage stars, quality this in can approach uses fixed SDSS pixel size. C2 uses fixed WFCAM GRBs/Rapid Response Telescopes utilizes a fixed H filter. spectrograph employing a grism for spectroscopy7 with a wavelength range giving a resolution of 1.8 nm (4 pixels), or with a roughly 9 ∼ mount providing horizon-to-horizon coverage to astronomers 24 hrs a day. The RCSto additionally observe can higher automatically interrupt priority scheduled transients, observations such as gamma-ray bursts. company set up by Liverpool JohnAstrophysics Moores Research University, Institute. which also owns LRT. It is operated by the 1.2.6 Reionization and Transients InfraRed (RATIR) camera PoS(HEASA 2016)001 Neil Gehrels 7 1 10 100 1000 Properties of 1234 BATSE GRBs. Figure 2: 0 0.01 0.1 100 The X-Shooter is the first second-generation instrument on the VLT, a very wide-band (UV to NIR) single-object spectrometer designed to exploresources, the such properties as of GRBs. rare, unusual or unidentified GRBs/Rapid Response Telescopes PoS(HEASA 2016)001 erg 10 ). The erg for − 3 process − 10 53 r for sGRBs Neil Gehrels × ◦ 10 7 (e.g., Foucart ∼ 15 ∼ c − 5 ∼ j 0.1–0.3 θ ∼ process material is dominated erg for lGRBs. These ranges − r 51 m). erg for sGRBs and µ 10 ´ nski 1998; Kulkarni 2005; Metzger, 51 1 − for lGRBs and and velocities ∼ 10 ◦ 50 5

∼ M 10 ∼ 1 j ∼ − θ 8 – 10 3 − process) nucleosynthesis following the decompression 10 for lGRBs. Although many of the details are uncertain, − r ∼ 1 − s 2 shows a compendium of 1234 BATSE GRBs. A further division − 1. 2 values at 11 hr post-GRB are similar between lGRBs and sGRBs erg for sGRBs and < ∼ z iso 50 − erg cm γ 10 9 E / − − X 49 10 L × 10 3 ∼ ∼ versus decays on much longer time-scales. The resulting energy release can power detectable 1 − β s Specific predictions for kilonova light curves are dependent on uncertainties such as the type of Gamma-ray bursts (GRBs) are intense flashes of radiation produced at cosmological distances Various groups have explored the supernova-like transient powered by this radioactive decay of Kasen et al. (2013) argue that the opacity of the expanding Ni, the ejecta from a disrupted NS is neutron rich and yields little Ni. Much heavier radioactive 2 2. GRBs come in two primary flavors, long and short, with the dividing point being roughly 2 s − 56 and ' ejecta (dynamical and/or disk outflows), ejectaculations masses, find and ejecta velocities. masses Recent in time the dependent range cal- spectra have broad absorption features and peak in the IR ( opacities are orders of magnitude larger thanresultant that light of curves ordinary should (e.g., be iron-rich) longer, supernova dimmer, ejecta. and redder The than previously thought (Figure et al. 2011; East & Pretorius 2012; Piran et al. 2013; Kyutoku, Ioka, & Shibata 2013; Hotokezaka can be made spectrally accordingredshift to range their is hardness from ratio about 0.2GRBs (i.e., to (lGRBs) ratio 2 the of for range high short is to GRBsenergy between low (sGRBs), release energies). about with is a 0.009 The mean and of 8.2, about with 0.4. a For mean long of about 2.3. The typical z (Kouveliotou et al. 1993). Figure material ejected from the NS (Eichler et al. 1989; Li & Paczy elements form via rapid neutron capture ( GRBs/Rapid Response Telescopes 2. Properties of GRBs are based on observedlGRBs, isotropic-equivalent and energies estimates of for jet beaming for each class, the two mechanisms are thought toLGRBs be are collapsars intrinsically for very lGRBs bright, and thelGRBs merging brightest neutron were explosions stars far in for above the sGRBs. Universe. detectorand The threshold. are highest seen redshift primarily SGRBs, nearby, by contrast, constitute a flux-limited sample, 3. Short GRBs and Kilonovae Piro, Quataert 2008; Metzger(dimmer et than a al. supernova and brighter 2010; thanemission a after Metzger nova) a would & produce NS-NS/NS-BH relatively Berger merger. isotropicof While optical/NIR 2012). SNIa light The curves are resultant powered “kilonova” primarily by decay of the ejecta from nuclearα densities. These newly synthesized elements undergo nuclear fission, by bound-bound transitions from those ionsthe with lanthanides. the most They complex valence compute electroncalculate atomic structure, the structure radiative i.e., transition models rates for for tens a of few millions of representative lines, ions and in find that order resulting to thermal emission once the ejecta expands sufficiently that photons can escape. cm (Gehrels et al. 2008). The sGRBs have weaker X-ray afterglows, a mean value of (Burrows et al. 2006,highly Grupe uncertain. et The al. 2006, Fong et al. 2012). Beaming angles for sGRBs are still PoS(HEASA 2016)001

2), M 2 = − l . Once 6000 K ) 10 1 = = + T Neil Gehrels l 2. Therefore can run from can run from 2 / l l ( 1 eject m 2 + M = 1), d-block ( g = 2 or l / , is 1 l 17. For − − can be 14 to 0), p-block ( s − process SN model (Kasen, Badnell, & m = − l r values R M 3. The periodic table is divided into four blocks 9 = l and concomitant 1 in which an electron can appear, for given − g 5, in good agreement with Tanaka & Hotokezaka (2013), Tanaka et al. . process (red) opacities. Also shown is a light curve calculated with a gray erg s (blue dashed line). − 15 r 1 42 − 2500 K (red dashed). The inset shows the corresponding bolometric light curves − g = = 2 –10 value of an atom’s valence shell: s-block ( is the principal quantum number, the magnetic quantum number H T , Barnes & Kasen (2013) calculate a peak absolute magnitude in the near-IR l 41 n c 3). In a given atom the orbital angular momentum quantum number M 1 10 . = 10 cm 0 ∼ l = = m) of Synthetic spectra (2.5 d after mass ejection) of the process opacities (red line). For comparison, also shown are blackbody curves with κ µ , including 0, and the electron spin quantum number − l 1, where 7 r . + − ejecta 1 A consideration of the structure of valence shell electrons in different blocks of elements in v n to ' l λ ( (2014), and Grossman et al. (2014). the periodic table reveals whyKasen the 2013). lanthanides The provide lanthanides thecharacterized and lion’s actinides by share reside orbital of in angular the the momentum f-block opacity of (Barnes the & periodic table, i.e., those and depending on the et al. 2013; Fernándezet & al. Metzger 2015). 2013; Assuming Sekiguchiluminosities iron-rich et supernova al. ejecta, Metzger 2015; & Foucart Berger et (2012) predict al. peak 2015; optical Fernández Figure 3: Barnes 2013), i.e., a “kilonova”, calculatedderived using Kurucz iron group opacities(black (black line) dashed) or and Autostructure- and f-block ( 0 to − assuming iron (black) or opacity of GRBs/Rapid Response Telescopes the number of potential states a specific electron is assigned a state, the Pauli exclusion principle posits that subsequent valence PoS(HEASA 2016)001 10 keV − 3 . Neil Gehrels X-ray Dux (erg s –1 cm –2 ) 0.6 d Absence ∼ (upper curve), and –11 –12 –13 –14

M 10 10 10 10 1 . F606W band and NIR data ). Therefore the number s m HST , l process kilonova optical emission X-ray F606W F160W m − 6 r , l 10 , 48 hr (our frame). This excess NIR flux n ∼ (lower curve) and 0 distinct states in an orbital is determined

Ni-driven decay component. The 0 g M 56 7 d (source frame). Model lines (Barnes & Kasen ∼ 01 . 10 35 at . 15 5 ) have been interpolated to the /XRT sensitivity by i 10 ≈ − 1 10 and AB Swift ) r J , ( Time since GRB 130603B (s) Time since GRB 130603B (d) Time since GRB 130603B g M valence electrons can be put into 4 v 10

21 22 23 24 25 26 27 28 29 AB magnitude AB

Optical, NIR and X-ray light curves of GRB 130603B (Tanvir et al. 2013). Left axis, optical and

/XRT data (Evans et al. 2007, 2009) are also consistent with breaking to a similarly steep decay (the Figure 4: NIR; right axis, X-ray. Optical data ( electrons cannot occupy that same quantum configuration ( have been interpolated to the F160Wof late-time band optical using emission an places average a spectral limit energy on distribution any at separate these are added to thesolid afterglow red curves. decay The curves cyan to curve shows produceis that negligible. predictions even the for brightest the predicted total NIR emission, shown as GRBs/Rapid Response Telescopes Swift dashed black line shows the optical lightalthough curve the simply source rescaled had to dropped match the below X-ray points in this time frame), 2013; orange curves) correspond to ejected masses of 0 of ways in which corresponds to absolute magnitude 3 PoS(HEASA 2016)001 5 = v 10 and ) = Neil Gehrels 1 2002 distinct + = ; there are 2 (some transitions 5 5 ∗ 2 C 4f 2 C 2 14 ( 2 ) = ) = Pm ( Fe or about 4 million - 100 times ( C 2 g ) 40,000 lines. Being a lanthanide, ' 2 2, and its electron configuration is 2002 ( 14 and = ∼ 210 l ∼ ) = 1 + 3 ∗ ). 11 2 5 ( . This gives the number of potential distinct energy 2 ] ! ) v ) = − g Pm ( ( ! g 3, and its electron configuration is [Xe]6s v [( = / l ! g ≡ 6 electrons in the valence shell. Thus v C = g v 210 distinct energy states, giving rise to = 6 ; there are C Abundances versus mass number for the three baseline r-process simulations (Surman et al. 2 10 4s 6 ) = The importance of the lanthanides vis a vis the opacity was not appreciated in the first detailed Let us compare the number of lines arising from valence electrons in Fe (iron) and Pm (prome- Fe ( energy states. Thus the number ofthat potential lines of for Fe! Pm is Forare ordinary so non-r-process low stellar that material this extra theopacity. absorbing relative power However, abundances per for of atom r-process is the material notrelatively lanthanides relevant the constant in with relative terms atomic abundances of number of the (Figure overall, the effective synthesized elements are being forbidden). [Ar]3d Pm is a f-block element, hence 2014): a parameterized wind(long-dashed hot r-process blue (solid line), red and line),abundances a (crosses) supernova are neutrino-driven neutron shown wind star for cold comparison merger r-process (Sneden r-process et (short-dashed al. 2008). green line). The scaledthium), solar for example. Fe is a d-block element, hence Figure 5: electrons in the valence shell. Thus configurations in an atomtransitions arising between distinct from states, the its number valence of lines electrons. varies approximately as Since absorption lines are due to GRBs/Rapid Response Telescopes by the choose function C PoS(HEASA 2016)001 Neil Gehrels 2 d) blue optical ∼ to optical peak was . In addition, current 0.25, preventing lan- 0 3 T > ∼ 10 ∼ 10 d) IR transient produced 3s before collapse to a BH. . ∼ 0 − 1 . 0 0.2 s in the Tanvir BAT. et al. (2013) ∼ process elements. It also offers hope ∼ − r 12 356 with a duration . 0 process elements in the universe (Freiburghaus, Rosswog, & = − z r 3, and the peak luminosity too high by a factor ∼ 0.3 s, the electron fraction in the wind ejecta will be > ∼ ). If correct, it would confirm that compact-object mergers are the progenitors 4 reverse shock, naked eye GRB In the standard fireball model, relativistic shells within a jet propagate away from the central GRB 130603B might be the first detected kilonova (Tanvir et al. 2013; Berger, Fong, & An additional complication in calculating spectra and light curves stems from the uncertain What are the prospects for observing a kilonova in conjunction with a sGRB? The biggest Swift engine and into the surroundingpropagates medium, back generating into a the jet. forward Studies shock of (FS). the A GRB reverse afterglow FS/RS shock emission (RS) can potentially provide present optical and near-infrared observationskilonova that (Figure provide strong evidence for an accompanying that kilonovae provide an alternative,sources unbeamed for electromagnetic direct signature detection of of the gravitational waves. most promising 4. Chornock 2013). It was a sGRB at Thielemann 1999; Goriely, Bauswein, & Janka 2011). of sGRBs and also the sites of significant production of lifetime of the hot merger remnant NS which may exist for problem is that, sinceafterglow. the kilonova The emission is only weak,Observational hope confirmation it of is such could for an usually event a wouldthe be be predominant sGRB masked important source given by occurring that of the this in stable mechanism normal may a be very low density interstellar medium. too long by a factor of calculations (Fontes et al.hundred 2017) fainter indicate than the in IRcalculations Metzger also using peaks et the extensive three al Los times Alamos (2010). opacitylations later codes. neglect and Fontes They lines is point et that out a al. are that factorlines most very atomic of while narrow; (2017) calcu- a conserving this present underestimates equivalent the width thediscuss most total increases two opacity. up the approaches, Broadening opacity to expansion these substantially. opacity date assumes and the Fontes opacity lines et broadening. are al. sparse Witheach (i.e., expansion (2017) non-overlapping) interaction opacity, so one as that a each scattering linegradient, event. can which be This helps treated leverages photons separately the diffuseassumes and Sobolev relative the approximation to lines for lines. are the denseline velocity In (i.e., once the it overlapping), opacity leaves which broadening the meansthese approach, previous two that one one. assumptions. a They photon Fontes also et quickly explore fully al. enters relativistic a versus (2017) semi-relativistic new delineate methods. a range of behavior spanning During this time the NSnucleosynthesis before winds lanthanides are are subject produced toproduce (Kasen, high transients Fernández, neutrino & more Metzger irradiation in 2015). whichkilonova accord light can This with curves will stop the will r-process be originaltransient due study coming to from by an the Metzger admixture outer lanthanide-free of etin ejecta, two the al and inner, components, a (2010). lanthanide a slower rich ( brief layers. Inremnant ( Kasen, general, Fernández, exists & for Metzger (2015) findthanide that production if and the hot thereby merger squelching the IR transient. GRBs/Rapid Response Telescopes work, by Metzger et al (2010), in which the interval from GRB start time PoS(HEASA 2016)001 and c ∼ RS Neil Gehrels v 6 10 NIR X-ray for comparison with the Radio Optical 4 Infrared -ray (KW) -ray (BAT) Ultraviolet Millimetric 5 γ γ 10 4 10 /BAT data are extrapolated down into the XRT Swift 3 , such a decomposition requires multi-wavelength 13 4 10 937, a peak visual magnitude 5.3, and a total energy . 10 0 10 ks. > ∼ = < 2 z data are scaled up by a factor of 10 ) Time since BAT trigger (s) 2 eff 0 Γ T 10 − t ( < detected the naked eye GRB 080319B (Racusin et al. 2008). It was Konus-Wind 5 ks . Swift ray flux densities (Racusin et al. 2008). The UV, optical and NIR data are normalized 1 10 band for 1 − 6 4 2 10 keV) for direct comparison with the XRT data. Combined X-ray and BAT data are scaled 1 γ –2 –4 −

− v 10 10 10

10 10 Flux density (mJy) density Flux 3 and the ejecta composition is the RS. The combination of large RS speed . Broadband light curve of the naked eye GRB 080319B, including radio, mm, IR, NIR, optical, eff Γ On 19 March 2008 the brightest optical burst ever observed. Ifthe it noon were sun 2 in kpc the from sky. Earth It it had would a have been redshift as bright as optical flux densities. Thisand figure optical includes data one from VLA KAIT, Nickel radio and data Gemini-South point (Bloom (Soderberg, et al. Chandra, 2009). & Frail 2008), bandpass (0 Figure 6: UV, X-ray and up by a factor of 45, and the to the UVOT observations spanning several orders of magnitude in frequency (Laskar et al. 2013). GRBs/Rapid Response Telescopes information about the explosion energy, geometry,Piran, and & structure of Narayan the 1998; circumburst Chevalier mediumfactor & (Sari, Li 2000). Thethe most finite useful and probe limited of ejecta the lengthearly-time initial means emission, bulk that basically Lorentz the optical only and/or hopeare radio of needed. detections. directly The observing RS To emission the be is RS detectablewell-defined expected is very to RS/FS via produce bright properties its a bursts synchrotron (Sari spectrum &Dai similar to 2005). Piran the There 1999ab; FS, have with Kobayashi been & detectionsdetailed of understanding Zhang hints of 2003ab; of RS an Zou, emission RS-likeenergy Wu, requires component distribution & a in (SED) careful a handful decomposition into of ofcomponents RS bursts. are the and related A afterglow by spectral FS a factor components. of Since the peak frequencies of the two PoS(HEASA 2016)001 − 27, 50 s 10 ' < ' m t m 6 Neil Gehrels 5 GRB 100219A GRB 3 is fainter than 800 s) shows the distinct = ) was observed with a wide z 6 < t < ray. The earliest data at 4 − γ ray light curves, indicating they arise from z − γ 3 14 800 s) is the afterglow produced as the external FS galaxies (red) with QSOs (black) and GRBs (blue), from z > t 2 erg (20 keV – 7 MeV). This burst (Figure 54 1 10 × 3 . QSO-DLAs Z from literature Z from X-shooter 1 solar metallicity solar = 0 iso E A comparison of metallicities of high ray emission indicated that the RS was at least mildly relativistic. Furthermore, the GRB 0.5 0.0

-2.5 -3.0 -2.0 -0.5 -1.0 -1.5

− γ metallicity rays GRBs are incredibly bright. A typical galaxy at a redshift of only − γ Figure 7: Thöne et al. (2011). Data are from Prochaska et al. (2003), Fynbo et al. (2006), andwhereas Savaglio et the al. optical (2009). component of GRB prompt emission, when seen, can be as high as the same physical region. The second optical component (50 s GRBs/Rapid Response Telescopes in variety of instruments spanning thereveal spectrum a from common radio shape to for the bright optical and characteristic of a RS, namely, anpower excess above law a decay. time-reversed The extrapolation final from the componentpropagates later into (at optical the surrounding medium.three Previous optical measurements components of in GRBs the haduntil same never the burst revealed prompt all with emission such faded. clarity.of The RS the high emission peak did luminosity not of become theoutflow visible could optical not RS have so been soon highly afterbeen magnetized the when suppressed. end it crossed On the RS theRS or other demands the RS hand, some itself magnetization, the would therefore have presence(Racusin an et of al. intermediate strong 2008). magnetization optical seems emission to accompanying be the indicated 5. Tools to Study the High-z Universe PoS(HEASA 2016)001 GRBs , from , from z 8 required 7 − c ˙ ρ Neil Gehrels 0.6 8 9 is the clumpiness of the 7 C 4 (Cucchiara et al. 2011). . 9 6 ' z 5 z 5 times larger than in QSOs (Figure ∼ t [Gyr] t 15 GRBs are providing information about the universe at a z = 40, 30, 20) 40, 30, and 20 (top to bottom), where (DLA) systems, originate in galaxies crossing sight lines. A esc = α 2 3 4 −

C / f esc f 4 2 1 (

c / LBG: Bouwens et al. (2008) B08 (LF integrated) LAE: Ota et al. (2008) GRB: (evolution corrected) ρ C the fraction of photons that escape their galaxy. 1 esc f 0 13 8 1 -3 -4 -2

0.1

10 10 10

*

ρ [M yr [M ] Mpc The cosmic star formation rate (SFR) history (Kistler et al. 2009), with data from several sources

3-3 -1 . GRBs are also being used to determine the star formation rate to high redshift (Figure intergalactic medium and to balance recombination, for Figure 8: (Hopkins & Beacom 2006; Bouwensare et shown al. as 2008; diamonds. Ota et The al. three dashed 2008). curves The (Madau rates et inferred from al. high 1999) give the critical SFR Thöne et al. 2011). GRBs/Rapid Response Telescopes 15. For GRBs,Multiwavelength the observations current of record high holder is GRB 090429B at Kistler et al. 2009;made see for also systematic Robertson effects that & alter Ellis thestar proportionality 2012; formation between rates, Trenti measured such et GRB as rates al. possible andthan metallicity inferred 2015). bias. from The other Corrections star techniques. need formation to ratetypes from GRBs be of GRBs galaxies. provide is a higher more complete measure of star formation from all time when it was onlyin about the 4% early of universe (Tanvir its etin current al. QSO age, 2009; spectra, and Salvaterra damped shed et Lyman study light al. of on 2009). the the Strong process DLA absorption of systemsdetailed lines reionization associated information detected with on optical the spectra metallicitymetallicity of history history GRBs of inferred and the from their universe,finds similar hosts and that studies has allowed the provided involving a metallicity QSOs. comparison for of GRBs For the on instance average Savaglio is (2006) PoS(HEASA 2016)001 Swift 0 to 2 = z Neil Gehrels 3. In addition GRB after- GRBs. About 3% of ≈ z 19 1920 @ @ 3 hr 20 min 19 @ 10 min 18 @ 23 hr 21 @ 1.5 hr 18 @ 3 hr 17 16 @ 2 min Swift ' ======3 (Berger et al. 2006). Numerous I I J . R K K K K H 4 in the source region. Absorption lines = 3 z − GRBs. z GRB afterglow spectroscopy. At low resolution (DLA) system. In addition one sees a wealth of z 16 High α − 8 – three have been seen to date. feature corresponding to a neutral hydrogen column > ∼ α z estimates (Bromm & Loeb 2002). Bromm & Loeb (2002) Table 1: gives the ten highest-redshift 1 Swift Table 2: High Redshift GRBs 10, while QSOs diminish rapidly beyond (Gyr) GRB Brightness ≈ z can detect GRBs to . The lines imply a density of 100 cm 2 has detected and positioned to arcsec accuracy 105 sGRBs. The afterglows are − look back 6 (Berger et al. 2006). Swift 5, lower than pre- cm > > Swift 8 13.0 120923A 22 z z z t 9.4 13.1 090429B 8.27.5 13.0 13.0 090423 100905A 6.7 12.8 080813 5.65.3 12.6 12.6 060927 050814 6.36.25.9 12.8 12.8 12.75.1 12.5 050904 120521C 130606A 060522 ∼ ’s fast localizations are enabling high presents an optical spectrum for GRB 050505 at 9 To date, GRBs, nature’s most powerful and luminous explosions, provide us with a means of studying Swift 6. Short GRB Update weak and fade fast, makinggiven by them Berger more (2009) difficult and tolack Fong study of stress et than on al. for the lGRBs.beaming uncertainties (2014) angles associated must Redshift or with limits be distributions many on treated of beaming with angles the are measurements. caution, based as In on there two particular, detections often is and often one upper a limit. lines are apparent, including adensity damped of Ly- 10 observed in infrared spectroscopic observations of GRB5% 050904 solar gave (Kawai a et metallicity al. measurement 2006), the of that first metallicity the determination observed at such evolution high in redshift,continues the demonstrating to mass- and luminosity- metallicity relationships from the early Universe. GRBsmetallicity. can (Lamb trace & the Reichart 2000; early Lambearly time 2002; times evolution Ciardi GRBs of & are star Loeb 2000; a formation,to Bromm hundred be reionization, & to detected and Loeb beyond a 2002). thousand At glows times have brighter simple than power-law spectra QSOs; lackingintergalactic they medium emission are (IGM). lines, also Table and expected henceGRBs are lie “clean” at probes of the also predict that metallic lines which can be usedlines to split infer into metal an abundances. array Atconditions of high associated resolution with fine-structure diffuse the transitions, radiation host in allowing absorption the anFigure host galaxy inference (Chen of et al. gas 2005; densities Berger et and al. of 2006). GRBs/Rapid Response Telescopes a typical host galaxy appears as a damped Ly- PoS(HEASA 2016)001 Neil Gehrels is the isotropic Chandra X-ray 52 , points may well be iso , , where K ◦ E 9 > ∼ absorption – solid line shows j 68 d (ID: 16708496, PI: A. . α Chandra θ , 8 − 39 / 1 0 = n 8 T / 1 − 52 , iso , K E 8 1 dex uncertainty. / 3 ± 17 ) is the circumstellar number density. Given (i) the z is the jet break time in days, 0 + n d , j 1 t ( 8 d / , j 3 t ◦ 5 erg, and . 9 52 = j 68 d implies a jet-break opening angle . θ 39 > j 94 d (ID: 16508492; PI: E. Troja) and t 05 and dashed lines indicate . . 7 22 = T ) = highlights the advantage in having prompt X-ray emission associated with sGRBs, at HI 10 ( N The optical spectrum of GRB 050505 (Berger et al. 2006). Lines are seen from the host galaxy at /XRT data points turned out to be due to an AGN, the two 275 and two foreground absorbers. Inset shows a zoom-in of the Ly . Figure Swift 4 = problematic nature of the association of the X-ray flux with GRB150101B and (ii) the questionable equivalent energy in units of 10 (Sari et al. 1999, Frail et al. 2001), where Observatory Levan). However, it is notthe clear that these data points are in fact related to GRB150101B. Just as and also the problemsGRB150101B. which This arise was in aoften ground-detected those problematic sGRB lacking to with a be very detection surethe late of of red follow-up. an points prompt association indicate In emission. of XRT emission such1056010. an which X-ray cases, Consider turned These detection it out with data to is the make beet GRB. a up al. known For the AGN, instance, 2007, GRB150101B 2MASX J12320498- 2009). light curve Fong on et the al. XRT public (2016) archive present (Evans two X-ray points taken from the Figure 9: z from AGN activity in the field. Thisand all therefore stems lacked from prompt the XRT fact emission that tothat GRB150101B provide was the ground-detected a jet good break localization. time Fong et al. then assume GRBs/Rapid Response Telescopes best fit log PoS(HEASA 2016)001 /XRT data is shown on Neil Gehrels z Swift 10 keV − 3 . 18 /BAT sGRB and therefore has an uncertain Swift Early-time X-ray emission for a sampling of sGRBs with secure redshifts. For comparison observations by E. Troja and A. Levan (presented in Fong et al. 2016) which could possibly be GRB150101B which was a ground-detected the same scale. The data in panels 1, 2, and 4, and the red points in panel 3 are 0 Figure 10: (Evans et al. 2007,Chandra 2009) taken from the publicassociated web with site. GRB150101B. The two black points in the third panel indicate GRBs/Rapid Response Telescopes PoS(HEASA 2016)001 Neil Gehrels 19 GRBs are the brightest and most powerful EM transients. A modern suite of rapid response [1] Abbott, B. 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