PoS(ICRC2019)555 http://pos.sissa.it/ , 5 , and G. Vianello 5 -LAT , N. Omodei 4 , 3 Fermi , M. Axelsson 2 , 1 ∗ [email protected] Speaker. In 2018, the Fermi mission celebratedTelescope its (LAT) has first decade been of very operation.from successful Gamma-Ray In in Bursts this (GRBs). detecting time, The the the analysis080916C, high-energy Large of GRB Area emission particularly 090510 remarkable (>100 and events GRB MeV) - 130427A suchwe - as present has GRB the been presented results in of dedicated aof publications. new GRBs systematic Here detected search in for high-energy 10ILE, emission years Integral from by and the IPN the full bursts, Fermi sample featuring a Gamma-Rayworks, detection and Burst efficiency returning Monitor, more 186 than as detections 50% well during bettera as 10 than vast years Swift, previous improvement of from AG- LAT the observations. 35 events This3 contained milestone years in marks of the Fermi first operations). LAT GRB We catalogwith assess (covering unprecedented the the sensitivity, characteristics covering first of aspects such the as GRB temporaltral population properties, at index energetics high of and energy spec- the high-energy emission.to inform Finally, we theory, in show particular how the the prospects LAT for observations very can high-energy be emission. used ∗ Copyright owned by the author(s) under the terms of the Creative Commons Dipartimento Interateneo di Fisica, Politecnico di Bari,Istituto Via Nazionale G. di Amendola Fisica 126, Nucleare 70125 (INFN) Bari, - Italy Sezione di Bari, Via E.Department Orabona of 4, Physics 70125 and Bari, Oskar Klein Center for Cosmoparticle Physics, Stockholm Department of Physics, KTH Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm, W.W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). 36th International Cosmic Ray Conference -ICRC2019- July 24th - August 1st, 2019 Madison, WI, U.S.A. on behalf of the1 Fermi-LAT Collaboration 2 Italy 3 University, SE-106 91 Stockholm, Sweden 4 Sweden 5 Cosmology, Department of Physics and SLACUniversity, National Stanford, Accelerator CA Laboratory, 94305, Stanford USA; E-mail: E. Bissaldi High-energy emission from GRBs: 10 years with PoS(ICRC2019)555 and ]. 05 3 T E. Bissaldi is the period 90 T ], and the Gamma- 1 ) is calculated as the 0 , -LAT (2FLGC) [ LAT T Fermi 1 ], namely the Burst and Transient Alert Telescipe 4 [ -LAT, covering the period from August 2008 to August 2018. A ], provide the combined capability of probing emission from GRBs 2 Fermi -LAT GRB catalog . ) is the period from the first to the last such photon. All these quantities were 1 1 , Fermi LAT is the time at which 5% of the total emission as been received, and T Neil Gehrels Swift Observatory 05 T until 95% of the emission has been detected. Gamma-Ray Space Telescope in the ten years since it was placed into orbit on 2008 June 05 T A separate detection analysis was run to see if the GRB was found in the LAT Low Energy For each trigger, a dedicated search was run to look for a high-energy counterpart in standard http://www.ssl.berkeley.edu/ipn3/ The 2FLGC presents the results of a search for high-energy counterparts of GRBs that trig- Gamma-ray bursts (GRBs) are the most luminous astrophysical events observed in the Uni- 1 , where 90 T from (LLE) data, which covers the rangerange from were 30 determined. MeV Onset to and 1 duration GeV. If are so, defined temporal using properties the also “standard” in quantities this of LAT data above 100 MeV. Thesearching search five was different time first windows performed from usingdetection 10 a s in to dedicated any 10 detection ks. time algorithm, All windowlimb triggers were contamination which manually or passed flaring inspected, the AGN. criteria tothe Only for rule analysis detections pipeline. out retained other Here, after sources, analyses thiseach were inspection such GRB, performed such were as to as passed Earth determine onset, to duration, a and number spectral of parameters. key The properties onset for ( calculated between 100 MeV and 100 GeV. (BAT), the X–Ray Telescope (XRT), ortary the Network UV–Optical (IPN) Telescope (UVOT), or by the Interplane- arrival time of the first photonthe with at duration least ( 90% probability of being associated with the GRB, and 2. The second gered space instruments and have antriggered available more public than localization. one After instrument, accounting weizations for had provided bursts a by that total the of GBM, 3044 unlesson-board independent a GRBs. the better We localization used was the provided local- by one of the instruments over seven decades inthe energy. highest These energy ground-breaking emission from observationscesses these have associated events, helped with furthered to GRBs, our helped characterize light, understanding the place gamma-ray of constraints opacity the of on the emission the Universe,collision-less pro- and Lorentz relativistic motivated shock revisions invariance in physics. of our Here basic the we understandingperiod speed summarize of of the of observations main with results from the first 10-year verse. They are briefoutflow flashes which is of thought high-energy to radiation originatenary emitted from systems a by (short stellar-mass an GRBs) black ultra-relativistic or holeFermi the collimated formed explosions by or the merging massive of stars11 bi- (long have given GRBs). the Observations opportunity byenergy to range. the study Its the two broadband scientific properties instruments, the of Large GRBs Area over Telescope an (LAT) [ unprecedented High-energy emission from GRBs 1. Introduction Ray Burst Monitor (GBM) [ full account is presented in the second catalog of GRBs detected by PoS(ICRC2019)555 1 1 E. Bissaldi 1 (50-300 keV) [s] G 1 T -LAT in the 10 years 1 1 1 1 1 1 1 1 1

1

(0.1-100 GeV) [s] GeV) (0.1-100 T Fermi ]. 3 1 1 1 1 (50-300 keV) [s] 2 1 GBM T . 1 2 1 ], which covered only 3 years of data and included 35 5 shows the same comparison of onset and duration at high 1 1 1 1 1 1 1

1 1

1 LAT (0.1-100 GeV) [s] GeV) (0.1-100 T -LAT GRB catalog [ (50-300 keV) [s] − -GBM Online Burst Catalog Fermi shows the comparison between the onset and duration in the 30 MeV–1 GeV range GBM T 2 − Onset (a) and duration (b) calculated in the 100 MeV–100 GeV energy range vs. the same Fermi − https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html As can be seen in the figure, our results confirm and strongly support the claim that when Figure The first In total, 186 GRBs (17 short and 169 long) were detected by

2

LAT (0.1-100 GeV) [s] GeV) (0.1-100 T GRBs, showed that emission aboveergies, 100 but MeV also is lasts typically longer. delayed Figure compared to that at lower en- covered by LLE and that atwhile 50–300 the keV. The duration onset time is is significantlyphotons here shorter very in in similar the in the both LLE lower energy range. part ranges, of Since the the LLE range, data the is similarities dominated indicate by that the component seen at 50– high–energy emission is observed in GRBs,that this in emission the is low–energy delayed and band.different lasts physical longer This processes compared also (e.g., to fits internalpanel with emission (c), the from scenario showing the where the jet50–300 the onset and keV two time external range, energy shocks). of bands adds the probe However, energy further high–energy emission information. starts emission already versus It during thelow-energy is the emission). burst clear period This duration that of means that the in in whatever promptto process the the is emission be majority behind active phase the very of (as high-energy early events, defined emission, on. it the by has the high (0.1–100 GeV) and low (50-300 keV)from energies the for the current study. The latter quantities are taken analysed. Of these, 169 werewere seen only detected above below 100 100 MeV MeV.so and This far. 91 gives the were largest found sample in of LLE high-energy data; GRB 17 detections of which 3. Temporal properties Figure 1: quantities calculated in the 50–300vs. keV energy the range. durations in Panel the (c)red 50–300 shows circles keV the represent energy onset long range. times and The short inwere GRBs, solid the outside respectively. line FoV 0.1–100 In at denotes GeV panel trigger where (c), time values we with are additionally a equal. mark thick Blue the orange and GRBs contour. which Figure from [ High-energy emission from GRBs PoS(ICRC2019)555 ], 9 , 8 , 7 E. Bissaldi 1 07. The stable decay . 1 0 1 ± (50-300 keV) [s] 80 . GBM T 1 1 1 1 1 1 1 1

1

LLE (30 MeV-1 GeV) [s] GeV) MeV-1 (30 T 3 -LAT preferentially detects GRBs with high fluence Fermi 04 with a standard deviation of 0 . 0 ]. ± 3 first compares the fluence in the 10–1000 keV range. While there is 99 3 . compares the values for GRBs included in this study, with the whole 3 (50-300 keV) [s] ] using BATSE data, as well as for several LAT-observed GRBs [ 6 − [ GBM T e.g. − − Onset times (left panel) and durations (right panel) calculated using LLE data in the 30 MeV–1

− − −

LLE (30 MeV-1 GeV) [s] GeV) MeV-1 (30 T As noted above, many GRBs show long-lasting emission at high energies. The large sample The left panel of Figure Previous studies have indicated that of GRBs in our sample88 enables GRBs us to had measure sufficient the datamean temporal to value decay provide of index a the of reliable index this decay is emission. index, 0 assuming In a total, power-law decay. The sample of GRBs detected by the GBM over the same 10-year period. and we can here confirm that it applies to the vast3.1 majority of Temporal decay GRBs (in particular long GRBs). a bias for the LAT tohave been detect detected. more This fluent is bursts, espceially there truethe for is fluence short a at GRBs large (red low points). spread, and and The high middle also panel energy some compares and fainter shows ones that the fluence is dominated by emission at lower 300 keV is driving theconsistent emission with the up hard-to-soft to evolution often at seen atbeen least lower reported energies. 30 by This MeV. behavior The has shorter previously duration in the LLE range is index is an indication thatis the responsible high-energy for emission the could afterglow befit emission related with in a to the broken the X-band. power-law, or same showways We component signs similar also that of to note variability the that in flares the some and lightcurve. GRBs plateaus These are seen are in better again X-rays. in some 4. Spectral index and energetics at lower energies. Figure Figure 2: GeV energy range vs.range. the corresponding The quantities solid calculated green usingGRBs, line GBM respectively. Figure denotes data from where in [ the value 50–300 are keV equal. energy Blue and red circles represent long and short High-energy emission from GRBs PoS(ICRC2019)555 1 and ] 3 E. Bissaldi 1 (0.1-100 GeV) [erg cm 1 GBM ) and at later times. Fluence 90 30 % is seen at 5 GeV. T ∼ 1

1 1 1 1 1 1

EXT Fluence ] cm [erg GeV) (0.1-100 70 % to ∼ 1 ] -LAT from a GRB so far is 95 GeV 1 Fermi (0.1-100 GeV) [erg cm 4 1 GBM Fluence 1

1 1 1 1 1 1

2.

Fluence (10 keV-1 MeV) [erg cm [erg MeV) keV-1 (10 Fluence ] − ]. 3 ], and only a few GRBs have reached energies above 50 GeV. However, 10 shows the fraction of GRBs detected above selected energy thresholds (250 MeV, ] experiments, show that GRBs are capable of producing emission at much greater 4 Left panel: The distribution of energy fluence calculated in the 10–1000 keV energy range for 11 Presented 2019 May 8 at the 1st International CTA symposium Figure The spectral energy distribution above 100 MeV is generally well-fit by a single power law. The maximum energy of a photon detected by 3 500 MeV, 1 GeV, 5 GeV, 10 GeV, 50 GeV). A sharp drop from energies. We have therefore studied the highest-energy photons for all the GRBs in our study. There are three GRBs with emission140928A above (52 50 GeV) GeV and (2 %), GRB namely 160509A GRB (52 130427A GeV). (95 GeV), GRB the recent detection of very high-energy (VHE) emission from GRBs by both the H.E.S.S. energies, which on average is about anthe order of high-energy magnitude fluence larger. The (0.1–100 right GeV) panel instead in compares the prompt phase (the GBM The photon index shows no(either sign during of prompt being or correlated extendedis neither times), some and with tendency is the similar that GBM for the durationGRBs, long the spectra nor and index of the is short short-duration flux compatible GRBs; with GRBs however, there tend to be harder. For both classes of High-energy emission from GRBs Interestingly, the values are oftencomes similar, at meaning later that times, a afterhas significant ceased. the part low-energy of emission the (and high-energy presumably flux the central4.1 engine High-energy activity) photon index 5. VHE emission from GRBs from GRB130427A [ MAGIC [ Figure 3: bursts detected by the LATtime compared to period. the Middle entire panel: samplein of Fluences the 2357 0.1–100 calculated GRBs GeV in detected energy theGBM. by range. 10–1000 The GBM All keV solid over values energy the green are range same lines estimatedshifted vs. denote in by where the factors fluences prompt values of calculated are time 10 windowrange equal. and as evaluated 100, in The measured respectively. the dashed by Right time and the panel: windowtime dashed-dotted after Fluences window. the green calculated Figure GBM lines in from emission are the [ vs. 0.1–100 the GeV same energy quantities evaluated in the prompt PoS(ICRC2019)555 4 and further ± 5 E. Bissaldi 49 − = dashed black line A ]. The figure also . The distribution ]. 4 3 12 . The 35 [ . , where 4 10 GeV, the highest energy B = > z ) + ). The distribution of the source-frame- 50% of the sGRBs. Figure 1MeV dashed green line / ∼ E ( 12 % (4 GRBs) above 100 GeV. The highest log ∼ × A 5 green solid line shows the energy of the highest-energy photon in each GRB as a 2 s from the trigger time for 5 < 21. It is tempting to connect this behavior to the underlying spectral distribution, such Fraction of GRBs with the highest energy photon detected above selected threshold energies (250 ± 266 The left panel of Fig. Although it is clear that the high-energy emission in general can last a long time, the highest- In our sample, there are also 34 GRBs with measured redshift, which allow us to study the = shows a more gradualmum decrease source-frame photon with energy energy: above 5 GeV, almost and 80 % ofincludes the a included linear GRBs fit to have theshowing a bin that centers maxi- the of fraction the of source-frameB distribution. GRBs The decreases fit as is remarkablythat good, we are seeing thefor limit all determined GRBs. by In the bright intrinsicbe bursts spectral observed. more shape, Faint high-energy which bursts emission seems will isphotons. to produce produced, be too allowing little similar GeV GeV emission emission to and the LAT will only detect MeV shows that also among thephoton GRBs is with in a some maximumParticle cases photon acceleration energy detected in GRBs before must thewithin be emission such efficient a in in short order the time. to 50–300 produce Considering such internal keV high-energy opacity energy gamma of range rays the is jet outflow over. also leads us to conclude energy photon in a given GRBthis in photon some cases arrives arrives within relatively soon after the trigger. For example, source-frame energy is a 147 GeV photon from GRB 080916C, at function of arrival time, normalized bybe the distinguished, duration in with the long 50–300 and keVin range. short the No bursts right clear overlapping pattern in panel can thedetected is almost right the 3 panel. ks short after The GRB thethe one trigger. 170127C, data clear This therefore where outlier GRB only the was cover the highest outside time the energy from LAT FoV photon around at 300 (500 s the MeV) after trigger was the time, trigger. and MeV, 500 MeV, 1 GeV, 5corrected GeV, 10 energies GeV, for 50 the GeV) ( redshiftdenotes a sample linear is fit indicated to the with values the corresponding to the center of each bin. Figure from [ Figure 4: source-frame-corrected energies. This is shown as the dashed line in Figure High-energy emission from GRBs PoS(ICRC2019)555 -LAT E. Bissaldi Fermi dashed vertical in the 1 keV–10 iso E . This indicates that the 5 18 GRB detections per year. The > ) in the 1 keV–10 MeV range. With the 12 to iso < E 6 represent long and short GRBs, respectively. Figure from 1 θ θ 1 red circles 1 and ) calculated in the 50–300 keV energy range (indicated by the 1 . More detailed studies are required in order to understand this behavior. , short and long GRBs occupy the same region. This points to similar 90 blue 1 5 iso E 1 Arrival Time/GBM T Time/GBM Arrival 1 1 Left panel: Energy vs. arrival time for the highest energy photon of each GRB. The arrival time is . 1 4

1 1 1 1 Max Photon Energy (MeV) Energy Photon Max https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermilgrb.html In this contribution we presented a summary of the main results from the second Previous results have hinted at a trend for the photons with highest source-frame energy to The 2FLGC corroborates some of the conclusions from the first catalog, such as the delayed 4 ). Right panel: Energy of the highest-energy photon calculated in the rest frame vs. ]. 3 In both panels of Figure maximum rest-frame energy produced isthere simply is a a function small ofenergies the despite number a total large of energy GRBs output. that However, deviate from the general trend, showing low rest-frame GRB catalog. Compared to the first GRBhave catalog, been several changes implemented, and improvements resulting to in the analysis a increase from conditions for the two classes. 6. Conclusions that a high bulk Lorentz factor is necessary in order for usappear to in be able the to GRBs detect with these photons. highest isotropic energy ( onset and longer duration forreflected the in high-energy the emission. 34 The GRBs larger sample with in measured this redshift. catalog is This also has allowed us to better investigate the line MeV range. In both panels, greater number of GRBs withextended known over redshift a in greater our study, range, the as trend shown not in only the persists but right is panel also of Figure results of the analysis for eachweb of site the 186 included GRBs are publicly available on the HEASARC Figure 5: normalized to the duration (T [ High-energy emission from GRBs PoS(ICRC2019)555 , , , 343 , ApJ E. Bissaldi , Science , 11 (2013) , GRB Coordinates 209 PoS (IFS2017) 065 , , ApJS , 791 (2009) , 1005 (2004) 702 611 , ApJ , ApJ 7 , 76 (2013) 774 , ApJ , 163 (2018) The First Fermi-LAT Gamma-Ray Burst Catalog Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A New Fermi-LAT Event Reconstruction Reveals More High-energy Gamma Rays The Large Area Telescope on the Fermi Gamma-Ray Space Telescope Mission , 386 (2002) GRB110721A: An Extreme Peak Energy and Signatures of the Photosphere 864 MAGIC detects the GRB 190114C in the TeV energy domain The Bright and the Slow - GRBs 100724B and 160509A with High-energy Cutoffs The Fermi Gamma-Ray Burst Monitor Exploring the low-energy domain of LAT-detected GRBs The Swift Gamma-Ray Burst Mission A Decade of Gamma-Ray Bursts Observed by Fermi-LAT: The Second GRB Catalog 579 , ApJ Implications of the Lag-Luminosity Relationship for Unified Gamma-Ray Burst -LAT Collaboration acknowledges support for LAT development, operation and , ApJ , 52 (2019) , 1071 (2009) Fermi 878 697 100 MeV , 31 (2012) ≤ from Gamma-Ray Bursts 42 (2014) Network 23701, 1 (2019) ApJ 757 Paradigms at ApJ The [9] G. Vianello, et al., [3] M. Ajello, et al., [4] N. Gehrels, et al., [5] M. Ackermann, et al., [1] W. B. Atwood, et al., [2] C. Meegan, et al., [8] E. Bissaldi, et al., [6] J. P. Norris, [7] M. Axelsson, et al., [10] M. Ackermann, et al., [11] R. Mirzoyan et al., [12] W. B. Atwood, et al., data analysis from NASAand and DOE INFN (United (Italy), States), MEXT,Swedish CEA/Irfu KEK, Research and and Council IN2P3/CNRS JAXA and (France), (Japan), thethe ASI National operations and Space phase the from Board INAF K.A. (Sweden). (Italy)work Wallenberg and was Science Foundation, CNES performed analysis (France) in the support is part in also underfrom DOE gratefully the Contract acknowledged. DE-AC02-76SF00515, European This and Union’s hasSkłodowska-Curie Horizon received grant support 2020 agreement No research 734303 and (NEWS). innovation programme under theReferences Marie High-energy emission from GRBs energetics also in the rest frame, forthat example while probing the detections highest-energy of photons. high-energy Thepotential photons results to remain show produce rare, photons a well significantcan over fraction be the of achieved 100 fairly GRBs quickly GeV have after limit the thebut seen trigger also so (as seen come far. in much Furthermore, the later MAGIC highthus detection (as energies require of in GRB a 190114C), combination the of H.E.S.S. rapidlyfield detection initiated of of observations view, and GRB Fermi extended will 180720B). follow-up. remain Future With a detections its key wide will component for such detections forAcknowledgments the foreseeable future.