J/A+A/573/A81 Spectral properties of energetic GRBs (Yu+, 2015)
Synchrotron cooling in energetic gamma-ray bursts observed by the
Fermi Gamma-Ray Burst Monitor.
Yu H.-F., Greiner J., van Eerten H., Burgess M.J., Bhat P.N., Briggs M.S.,
Connaughton V., Diehl R., Goldstein A., Gruber D., Jenke P.A.,
von Kienlin A., Kouveliotou C., Paciesas W.S., Pelassa V., Preece R.D.,
Roberts O.J., Zhang B.-B.
<Astron. Astrophys., 573, A81-81 (2015)>
=2015A&A...573A..81Y 2015A&A...573A..81Y
ADC_Keywords: Gamma rays
Keywords: gamma rays: stars - gamma-ray burst: general -
radiation mechanisms: non-thermal - methods: data analysis
Abstract:
We study the time-resolved spectral properties of energetic gamma-ray
bursts (GRBs) with good high-energy photon statistics observed by the
Gamma-Ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space
Telescope.
We aim to constrain in detail the spectral properties of GRB prompt
emission on a time-resolved basis and to discuss the theoretical
implications of the fitting results in the context of various prompt
emission models.
Our sample comprises eight GRBs observed by the Fermi GBM in its first
five years of mission, with 1keV-1MeV fluence f>1.0x10-4erg/cm2 and
a signal-to-noise ratio level of S/N≥10.0 above 900keV. We performed
a time-resolved spectral analysis using a variable temporal binning
technique according to optimal S/N criteria, resulting in a total of
299 time-resolved spectra. We performed Band function fits to all
spectra and obtained the distributions for the low-energy power-law
index α, the high-energy power-law index β, the peak energy
in the observed νFν spectrum Ep, and the difference between
the low- and high-energy power-law indices Δs=α-β. We
also applied a physically motivated synchrotron model, which is a
triple power-law with constrained power-law indices and a blackbody
component, to test the prompt emission for consistency with a
synchrotron origin and obtain the distributions for the two break
energies Eb,1 and Eb,2, the middle segment power-law index β,
and the Planck function temperature kT.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 60 8 The names, GBM trigger numbers, durations,
fluence, detectors used, and optimal S/N for
the eight bursts studied in this paper
tablea1.dat 88 34 Band parameters for GRB 090902B
tablea2.dat 88 34 Band parameters for GRB 100724B
tablea3.dat 88 52 Band parameters for GRB 100826A
tablea4.dat 88 44 Band parameters for GRB 101123A
tablea5.dat 88 27 Band parameters for GRB 120526A
tablea6.dat 88 37 Band parameters for GRB 130427A
tablea7.dat 88 39 Band parameters for GRB 130504C
tablea8.dat 88 32 Band parameters for GRB 130606B
--------------------------------------------------------------------------------
See also:
J/ApJS/199/18 : The Fermi GBM catalog (Paciesas+, 2012)
J/ApJS/207/39 : IPN supplement to the Fermi GBM (Hurley+, 2013)
J/ApJS/211/13 : The second Fermi/GBM GRB catalog (4yr) (von Kienlin+, 2014)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- GRB GRB name (YYMMDDA)
9- 18 F10.3 --- Trig GBM Trigger number (YYMMDD.ddd)
20- 24 F5.1 s T90 Duration
26- 28 F3.1 s e_T90 rms uncertainty on T90
30- 34 F5.2 10-7J/m2 Fluence 1keV-1MeV fluence
36- 40 F5.3 10-7J/m2 e_Fluence rms uncertainty on Fluence
42- 51 A10 --- NaI NaI detector(s) used
53- 54 A2 --- BGO BGO detector used
56- 57 I2 --- S/N [20/50] Optimal signal-to-noise ratio
59- 60 A2 --- Table Name of the table with band parameters
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea?.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.3 s tstart Starting time relative to the GBM
trigger time T0
9- 15 F7.3 s tstop Stop time relative to the GBM
trigger time T0
17 A1 --- l_A Limit flag on A
18- 23 F6.4 ph/s/cm2/keV A Normalization factor at 100keV (1)
25- 30 F6.4 ph/s/cm2/keV e_A ? rms uncertainty on A
32 A1 --- l_Ep Limit flag on Ep
33- 38 F6.1 keV Ep Peak energy Ep (1)
40- 44 F5.1 keV e_Ep ? rms uncertainty on Ep
46 A1 --- l_alpha Limit flag on alpha
47- 52 F6.3 --- alpha Low-energy power-law index α (1)
54- 58 F5.3 --- e_alpha ? rms uncertainty on alpha
60 A1 --- l_beta Limit flag on beta
61- 67 F7.3 --- beta High-energy power-law index β (1)
69- 75 F7.3 --- e_beta ? rms uncertainty on beta
77- 84 F8.2 --- CSTAT Castor C-statistics value (good match for
low values, <1000)
85 A1 --- --- [/]
86- 88 I3 --- dof [239/478] Degrees of freedom
--------------------------------------------------------------------------------
Note (1): parameters of the BAND function (1993ApJ...413..281B 1993ApJ...413..281B):
f(E) = A (E/100keV)α exp[-(α+2)E/Ep] (for E<Ec)
f(E) = A (E/100keV)β exp[β-α] (Ep/100keV)α-β
(for E≥Ec)
Ec = ((α-β)/(α+2))Ep
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Feb-2015