2020A&A...640A..91Y


Query : 2020A&A...640A..91Y

2020A&A...640A..91Y - Astronomy and Astrophysics, volume 640A, 91-91 (2020/8-1)

A new fitting function for GRB MeV spectra based on the internal shock synchrotron model.

YASSINE M., PIRON F., DAIGNE F., MOCHKOVITCH R., LONGO F., OMODEI N. and VIANELLO G.

Abstract (from CDS):


Aims. The physical origin of the gamma-ray burst (GRB) prompt emission is still a subject of debate. Internal shock models have been widely explored, owing to their ability to explain most of the high-energy properties of this emission phase. While the Band function or other phenomenological functions are commonly used to fit GRB prompt emission spectra, we propose a new parametric function that is inspired by an internal shock physical model. We use this function as a proxy of the model to compare it easily to GRB observations.
Methods. We built a parametric function that represents the spectral form of the synthetic bursts provided by our internal shock synchrotron model (ISSM). We simulated the response of the Fermi instruments to the synthetic bursts and fit the obtained count spectra to validate the ISSM function. Then, we applied this function to a sample of 74 bright GRBs detected by the Fermi GBM, and we computed the width of their spectral energy distributions around their peak energy. For comparison, we also fit the phenomenological functions that are commonly used in the literature. Finally, we performed a time-resolved analysis of the broadband spectrum of GRB 090926A, which was jointly detected by the Fermi GBM and LAT. This spectrum has a complex shape and exhibits a power-law component with an exponential cutoff at high energy, which is compatible with inverse Compton emission attenuated by gamma-ray internal absorption.
Results. This work proposes a new parametric function for spectral fitting that is based on a physical model. The ISSM function reproduces 81% of the spectra in the GBM bright GRB sample, versus 59% for the Band function, for the same number of parameters. It gives also relatively good fits to the GRB 090926A spectra. The width of the MeV spectral component that is obtained from the fits of the ISSM function is slightly larger than the width from the Band fits, but it is smaller when observed over a wider energy range. Moreover, all of the 74 analyzed spectra are found to be significantly wider than the synthetic synchrotron spectra. We discuss possible solutions to reconcile the observations with the internal shock synchrotron model, such as an improved modeling of the shock microphysics or more accurate spectral measurements at MeV energies.

Abstract Copyright: © M. Yassine et al. 2020

Journal keyword(s): gamma-ray burst: general - radiation mechanisms: non-thermal

VizieR on-line data: <Available at CDS (J/A+A/640/A91): tablea4.dat>

Simbad objects: 83

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Number of rows : 83
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 Fermi bn131231198 gB 00 42 21.66 -01 39 10.6           ~ 73 0
2 Fermi bn110921912 gB 01 12 -27.8           ~ 13 0
3 Fermi bn100322045 gB 01 25 -12.4           ~ 17 0
4 Fermi bn101014175 gB 01 47.8 -51 04           ~ 24 0
5 Fermi bn140306146 gB 01 52 +49.0           ~ 9 0
6 Fermi bn120129580 gB 02 02 +59.3           ~ 14 0
7 Fermi bn160802259 gB 02 21 +72.7           ~ 15 0
8 Fermi bn140416060 gB 02 22 +43.9           ~ 10 0
9 Fermi bn100324172 gB 02 39 -19.3           ~ 18 0
10 Fermi bn081125496 gB 02 51 -18.9           ~ 27 0
11 Fermi bn110825102 gB 02 59 11.59 +15 25 38.4           ~ 23 0
12 Fermi bn130609902 gB 03 35 05.11 -40 10 26.7           ~ 38 0
13 Fermi bn131028076 gB 03 48 +72.2           ~ 10 0
14 Fermi bn130502327 gB 04 27 02.90 +71 03 38.5           ~ 24 0
15 Fermi bn101126198 gB 05 39 -22.6           ~ 16 0
16 Fermi bn090820027 gB 05 51 +27.1           ~ 38 0
17 Fermi bn100829876 gB 06 02 +30.3           ~ 15 0
18 Fermi bn090328401 gB 06 02 39.69 -41 52 55.1           ~ 153 1
19 Fermi bn130504978 gB 06 06 31.29 +03 50 02.0           ~ 21 0
20 Fermi bn120711115 gB 06 18 42.839 -70 59 56.78           ~ 84 0
21 Fermi bn090809978 gB 06 21 +00.2           ~ 28 0
22 Fermi bn100511035 gB 07 17.2 -04 39           ~ 22 0
23 Fermi bn120426090 gB 07 26 -65.6           ~ 14 0
24 Fermi bn081207680 gB 07 29.6 +70 30           ~ 24 0
25 Fermi bn100719989 gB 07 33 +05.4           ~ 11 0
26 Fermi bn150627183 gB 07 49 52.95 -51 29 22.5           ~ 16 0
27 Fermi bn140810782 gB 07 56 +27.5           ~ 12 0
28 Fermi bn080916009 gB 07 59 23.24 -56 38 16.8           ~ 334 0
29 Fermi bn120119170 gB 08 00 06.940 -09 04 53.83           ~ 138 0
30 Fermi bn081215784 gB 08 22 +54.0           ~ 49 0
31 Fermi bn091128285 gB 08 31 +01.7           ~ 17 0
32 Fermi bn140523129 gB 08 52 26.70 +24 57 25.6           ~ 18 0
33 Fermi bn110622158 gB 08 56 +19.5           ~ 10 0
34 Fermi bn080817161 gB 10 05 09.600 -19 15 36.00           ~ 24 0
35 Fermi bn160905471 gB 10 48 59.06 -50 48 03.9           ~ 21 0
36 Fermi bn120624933 gB 11 23 31.98 +08 55 42.1           ~ 70 0
37 Fermi bn111216389 gB 12 24 +05.8           ~ 9 0
38 Fermi bn090424592 gB 12 38 07.40 +16 49 45.9           ~ 219 0
39 Fermi bn101231067 gB 12 47 +17.6           ~ 10 0
40 Fermi bn100414097 gB 12 48 30.0 +08 41 35           ~ 107 0
41 Fermi bn100724029 gB 12 58 10.38 -11 06 09.3           ~ 143 0
42 Fermi bn081224887 gB 13 26.8 +75 06           ~ 28 0
43 Fermi bn150902733 gB 14 19 54.18 -69 21 09.9           ~ 20 0
44 Fermi bn130327350 gB 14 31 30.57 -69 24 15.4           ~ 21 0
45 Fermi bn130606497 gB 14 34 07.04 -22 06 08.2           ~ 31 0
46 Fermi bn160910722 gB 14 45 46.04 +39 04 01.3           ~ 32 0
47 Fermi bn091120191 gB 15 07.2 -21 47           ~ 30 0
48 Fermi bn120328268 gB 15 12 +22.8           ~ 17 0
49 Fermi bn110301214 gB 15 17.4 +29 24           ~ 39 0
50 Fermi bn080825593 gB 15 28.8 -04 54           ~ 64 0
51 Fermi bn100910818 gB 15 52.4 -34 37           ~ 14 0
52 Fermi bn150118409 gB 16 01 -35.8           ~ 11 0
53 Fermi bn091003191 gB 16 46 04.680 +36 37 31.08           ~ 111 0
54 Fermi bn140508128 gB 17 01 51.95 +46 46 49.5           ~ 51 0
55 Fermi bn090902462 gB 17 39 45.26 +27 19 28.1           ~ 352 0
56 Fermi bn111220486 gB 17 50 -56.0           ~ 8 0
57 Fermi bn090718762 gB 18 16 -36.4           ~ 20 0
58 Fermi bn111003465 gB 18 27 -62.3           ~ 10 0
59 Fermi bn130306991 gB 18 37 50.75 -11 40 52.4           ~ 21 0
60 Fermi bn110731465 gB 18 42 00.99 -28 32 13.8           ~ 137 0
61 Fermi bn100826957 gB 18 56 -23.2           ~ 61 0
62 Fermi bn110625881 gB 19 06 55.85 +06 45 19.2           ~ 55 0
63 Fermi bn120707800 gB 19 24 -34.4           ~ 15 0
64 Fermi bn120204054 gB 19 30 -03.6           ~ 8 0
65 Fermi bn090618353 gB 19 36 01.80 +78 21 07.1           ~ 294 0
66 Fermi bn110921577 gB 19 36 23.46 +36 19 43.0           ~ 38 0
67 Fermi bn120226871 gB 20 12 +48.7           ~ 16 0
68 Fermi bn100918863 gB 20 34 -46.0           ~ 12 0
69 Fermi bn150403913 gB 20 46 01.17 -62 42 40.1           ~ 68 0
70 Fermi bn090528516 gB 20 49 +32.7           ~ 26 0
71 Fermi bn110717319 gB 20 51 -14.8           ~ 10 0
72 Fermi bn101023951 gB 21 11 51.26 -65 23 17.7           ~ 60 0
73 Fermi bn090829672 gB 21 56.8 -34 12           ~ 27 0
74 Fermi bn150330828 gB 21 57 +50.0           ~ 12 0
75 Fermi bn110721200 gB 22 10 -38.6           ~ 123 0
76 Fermi bn130720582 gB 22 32 -09.4           ~ 3 0
77 Fermi bn090719063 gB 22 45 -67.9           ~ 36 0
78 Fermi bn131118958 gB 23 20 -66.8           ~ 6 0
79 Fermi bn100707032 gB 23 24 -06.6           ~ 40 0
80 Fermi bn100612726 gB 23 28 -01.8           ~ 20 0
81 Fermi bn110729142 gB 23 34 +05.0           ~ 9 0
82 Fermi bn090926181 gB 23 33 36.18 -66 19 25.9           ~ 276 0
83 Fermi bn130518580 gB 23 42 39.79 +47 27 55.2           ~ 60 0

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2022.09.26-13:40:08

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