2022A&A...657A.111H


Query : 2022A&A...657A.111H

2022A&A...657A.111H - Astronomy and Astrophysics, volume 657A, 111-111 (2022/1-1)

Searching for an additional high-energy component in Fermi-LAT GRB afterglows.

HE X.-B., TAM P.-H.T., LONG G.-B., PAL P.S., ZHANG Y. and ZHANG L.-J.

Abstract (from CDS):


Context. The very high-energy (VHE; ≥100 GeV) component from at least two gamma-ray bursts (GRBs), that is, GRB 180720B and GRB 190114C, has been detected in the afterglow phase. It is widely discussed that the GeV to TeV emission originated from a synchrotron self-Compton (SSC) process. The VHE component may cause an upturn at the high-energy spectral ends in the Fermi-Large Area Telescope (Fermi-LAT) observing band.
Aims. We aim to find out whether an additional high-energy component commonly exists in the afterglows of Fermi-LAT GRBs. This study will help us to better understand how common it is for a GRB afterglow detected by Fermi-LAT to involve a VHE component.
Methods. First, we selected the GRBs that emit ≥10 GeV photons. The ≥10 GeV photons can be considered as a plausible proxy for a VHE component. We systematically analyzed 199 GRBs detected by Fermi-LAT from 2008-2019. If an additional high-energy component exists in the afterglows of Fermi-LAT GRBs, the best-fit spectral model could be a broken power law (BPL) model with an upturn above a break energy. We compared the afterglow spectra using power-law (PL) and BPL representations.
Results. Out of the 30 GRBs with ≥10 GeV photons that arrived after T90 (the time duration when 90% of the prompt emission was detected), 25 GRBs are tentatively or significantly detected at 0.1-200 GeV after 2 x T90. The spectrum of GRB 131231A shows an upturn above an energy break of 1.6 ±0.8 GeV, supporting the BPL model. For GRB 131231A, we performed a modeling of its X-ray and γ-ray spectra and found that the SSC model can explain the upturn with acceptable parameter values. In the cases of GRB 190114C, GRB 171210A, GRB 150902A, GRB 130907A, GRB 130427A, and GRB 090902B, the improvement of the BPL fit compared to the PL fit is tentative or marginal.
Conclusions. There is no conclusive evidence that an additional higher energy component commonly exists in Fermi-LAT GRB afterglows, except for the group of Fermi-LAT GRBs mentioned above. Such an additional high-energy component may be explained by the SSC mechanism. Current and future VHE observations will provide important constraints on the issue.

Abstract Copyright: © ESO 2022

Journal keyword(s): gamma rays: stars - radiation mechanisms: non-thermal - relativistic processes - gamma-ray burst: general

Simbad objects: 36

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Number of rows : 36
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 GRB 180720B gB 00 02 06.99 -02 55 07.8           ~ 97 0
2 Fermi bn131231198 gB 00 42 21.66 -01 39 10.6           ~ 78 0
3 Fermi bn101014175 gB 01 47.8 -51 04           ~ 24 0
4 Fermi bn140416060 gB 02 22 +43.9           ~ 10 0
5 GRB 160422A gB 02 48 22.69 -57 52 29.9           ~ 14 0
6 Fermi bn140928437 gB 02 54 47.72 -55 55 43.5           ~ 18 0
7 SN 2019oyw SN* 02 58 10.510 -08 57 27.20           ~ 94 0
8 GRB 190114C gB 03 38 01.18 -26 56 47.8           ~ 177 0
9 Fermi bn120526303 gB 04 25 -32.2           ~ 13 0
10 Fermi bn171010792 gB 04 26 19.41 -10 27 47.9           ~ 57 0
11 Fermi bn130502327 gB 04 27 02.90 +71 03 38.5           ~ 24 0
12 Fermi bn160310016 gB 06 35 17.33 -07 12 56.0           ~ 19 0
13 Fermi bn100511035 gB 07 17.2 -04 39           ~ 22 0
14 Fermi bn140810782 gB 07 56 +27.5           ~ 12 0
15 Fermi bn080916009 gB 07 59 23.24 -56 38 16.8           ~ 343 0
16 Fermi bn140619475 gB 08 51 -09.7           ~ 22 0
17 Fermi bn160521385 gB 09 50 39.92 +79 01 50.5           ~ 15 0
18 SN 2013cq SN* 11 32 32.84 +27 41 56.2           SNIc 463 1
19 Fermi bn100414097 gB 12 48 30.0 +08 41 35           ~ 110 0
20 Fermi bn110903111 gB 13 08 15.82 +58 58 53.8           ~ 24 0
21 Fermi bn120916173 gB 13 43.2 +36 40           ~ 12 0
22 Fermi bn150902733 gB 14 19 54.18 -69 21 09.9           ~ 21 0
23 GRB 130907A gB 14 23 34.03 +45 36 27.1           ~ 91 0
24 Fermi bn171022885 gB 14 28 +11.9           ~ 7 0
25 GRB 090427A gB 15 43.4 -14 03           ~ 2 0
26 Fermi bn090902462 gB 17 39 45.26 +27 19 28.1           ~ 362 0
27 GRB 100213C gB 18 49.8 +15 09           ~ 3 0
28 Fermi bn100116897 gB 20 20 +14.4           ~ 35 0
29 Fermi bn160625945 gB 20 34 23.67 +06 55 11.1           ~ 141 0
30 Fermi bn160509374 gB 20 47 00.90 +76 06 30.1           ~ 90 0
31 Fermi bn160623209 gB 21 01 11.54 +42 13 15.5           ~ 50 0
32 Fermi bn140206275 gB 21 01 -08.5           ~ 20 0
33 Fermi bn090510016 gB 22 14 12.60 -26 35 51.1           ~ 473 1
34 Fermi bn171210493 gB 22 21 09.6 +24 26 24           ~ 15 0
35 Fermi bn090926181 gB 23 33 36.18 -66 19 25.9           ~ 284 0
36 GRB 120919B gB ~ ~           ~ 5 0

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2023.01.30-21:50:16

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