J/ApJ/886/20 Bayesian time-resolved spectra of Fermi GBM pulses (Yu+, 2019)
Bayesian time-resolved spectroscopy of GRB pulses.
Yu H.-F., Dereli-Begue H., Ryde F.
<Astrophys. J., 886, 20 (2019)>
=2019ApJ...886...20Y 2019ApJ...886...20Y
ADC_Keywords: GRB
Keywords: catalogs ; gamma-ray burst: general ; methods: statistical
Abstract:
We performed time-resolved spectroscopy on a sample of 38 single
pulses from 37 gamma-ray bursts detected by the Fermi/Gamma-ray Burst
Monitor during the first 9yr of its mission. For the first time a
fully Bayesian approach is applied. A total of 577 spectra are
obtained and their properties studied using two empirical photon
models, namely the cutoff power law (CPL) and Band model. We present
the obtained parameter distributions, spectral evolution properties,
and parameter relations. We also provide the result files containing
this information for usage in further studies. It is found that the
CPL model is the preferred model, based on the deviance information
criterion and the fact that it consistently provides constrained
posterior density maps. In contrast to previous works, the high-energy
power-law index of the Band model, β, has in general a lower
value for the single pulses in this work. In particular, we
investigate the individual spectrum in each pulse, that has the
largest value of the low-energy spectral indexes, α. For these
38 spectra, we find that 60% of the α values are larger than
-2/3, and thus incompatible with synchrotron emission. Finally, we
find that the parameter relations show a variety of behaviors. Most
noteworthy is the fact that the relation between α and the
energy flux is similar for most of the pulses, independent of any
evolution of the other parameters.
Description:
In summary, we have defined a sample of 38 single pulses from 37 GRBs
out of 2050 Fermi/GBM detected bursts from 2008 July until 2017 March.
A total of 577 time-resolved spectra were obtained and their spectral
properties investigated using a fully Bayesian method.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 105 38 GRB, detectors, source and background intervals
used in the analysis
table3.dat 309 577 Time-resolved spectral analysis results
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See also:
J/ApJS/166/298 : Spectral cat. of bright BATSE gamma-ray bursts (Kaneko+, 2006)
J/ApJ/756/112 : Fermi/GBM GRB time-resolved spectral analysis (Lu+, 2012)
J/ApJS/216/32 : Localizations of GRBs with Fermi GBM (Connaughton+, 2015)
J/A+A/588/A135 : Fermi/GBM GRB time-resolved spectral catalog (Yu+, 2016)
J/ApJS/223/28 : The third Fermi/GBM GRB catalog (6yr) (Bhat+, 2016)
J/ApJ/893/46 : The fourth Fermi-GBM GRB catalog: 10yrs (von Kienlin+, 2020)
http://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html : Fermi GBM burst
online catalog
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 I09 --- Fermi [81009140/170114917] GRB identifier
(<Fermi bnYYMMDDddd> in Simbad)
11- 20 A10 --- Det Detectors (1)
22- 24 I3 s b_delTs [-5/160] Source lower range ΔTsrc
26- 28 I3 s B_delTs [9/200] Source upper range ΔTsrc
30- 32 I3 s b_delTb1 [-40/100] First background lower range
ΔTbkg,1
34- 36 I3 s B_delTb1 [-15/150] First background upper range
ΔTbkg,1
38- 40 I3 s b_delTb2 [0/250]? Second background lower range
ΔTbkg,2
42- 44 I3 s B_delTb2 [30/300]? Second background upper range
ΔTbkg,2
46- 47 I2 s b_delTb3 [0/60]? Third background lower range
ΔTbkg,3
49- 50 I2 s B_delTb3 [80/80]? Third background upper range
ΔTbkg,3
52- 53 I2 --- N [8/30] The number of time bins using Bayesian
blocks across the source interval
55- 56 I2 --- Ns [5/19] The number of time bins with
statistical significance of at least 20
58 A1 --- a-Ep α-Ep type (2)
60- 64 F5.2 --- r(a-Ep) [-0.86/0.93] Spearman's rank coefficient
for α-Ep
66 I1 --- F-Ep [1/3] F-Ep type (2)
68- 72 F5.2 --- r(F-Ep) [-0.83/0.95] Spearman's rank coefficient
for F-Ep
74 I1 --- F-a [1/3] F-α type (2)
76- 80 F5.2 --- r(F-a) [-0.71/0.98] Spearman's rank coefficient
for F-α
82- 105 A24 --- Evol Evolutionary trend of the peak energy (3)
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Note (1): The detector in brackets is the brightest one, used for background
and Bayesian block fitting.
Note (2): The type of relations for parameter pairs α-Ep, F-Ep, and
F-α, where α is the low-energy power-law index, Ep is the
spectral peak, and F is the energy flux.
Note (3): Spectral evolution is detailed in Section 3.3.
i.t. = pure intensity tracking evolution
h.t.s. = pure hard-to-soft evolution
s.t.h. = soft-to-hard evolution
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [GRB]
4- 12 I9 --- Fermi GRB identifier
13 A1 --- --- [;]
15- 23 A9 --- m_Fermi Pulse identifier
25- 30 F6.2 s tStart [-5/194] Start time of Bayesian block
time bin
32- 37 F6.2 s tStop [-4/200] Stop time of Bayesian block
time bin
39- 44 F6.2 --- S [-4.4/197] Significance of the bin
46- 52 E7.2 ph/s/cm2/keV K [0.009/737] Best-fit CPL
normalization parameter
54- 60 E7.2 ph/s/cm2/keV E_K [0.0002/427] Upper uncertainty in K
62- 68 E7.2 ph/s/cm2/keV e_K [0.007/401] Lower uncertainty in K
70- 74 F5.2 --- alpha [-2.9/0.5] Best-fit CPL low-energy
power-law index
76- 79 F4.2 --- E_alpha [0/0.7] Uncertainty in alpha
81- 84 F4.2 --- e_alpha [0.02/1.1] Uncertainty in alpha
86- 93 F8.2 keV Ec [14/44331] Best-fit CPL cutoff energy
95- 102 F8.2 keV E_Ec [0.8/13666] Upper uncertainty in Ec
104- 111 F8.2 keV e_Ec [2.1/35094] Lower uncertainty in Ec
113- 120 F8.2 keV Ep [-4024/57237] Derived CPL peak energy
122- 129 F8.2 keV E_Ep [0.04/17645] Upper uncertainty in Ep
131- 138 F8.2 keV e_Ep [0.2/45310] Lower uncertainty in Ep
140- 146 E7.2 mW/m2 F [1e-9/2.6e-5] Derived CPL energy
flux; erg/s/cm2
148- 156 E9.2 mW/m2 E_F [1e-8/0.00011] Upper uncertainty in F
158- 164 E7.2 mW/m2 e_F [1e-9/1.3e-5] Lower uncertainty in F
166- 172 E7.2 ph/s/cm2/keV K-B [0.0008/405] Best-fit BAND
normalization parameter
174- 180 E7.2 ph/s/cm2/keV E_K-B [2e-5/154] Upper uncertainty in K-B
182- 188 E7.2 ph/s/cm2/keV e_K-B [0.0005/402] Lower uncertainty in K-B
190- 194 F5.2 --- alpha-B [-1.8/2.5] Best-fit BAND low-energy
power-law index
196- 199 F4.2 --- E_alpha-B [0.01/3.3] Upper uncertainty in
alpha-B
201- 204 F4.2 --- e_alpha-B [0/3.1] Lower uncertainty in alpha-B
206- 210 F5.2 --- Beta-B [-4.7/-1.6] Best-fit BAND high-energy
power-law index
212- 215 F4.2 --- E_Beta-B [0.03/1.7] Upper uncertainty in
Beta-B
217- 220 F4.2 --- e_Beta-B [0/1.7] Lower uncertainty in Beta-B
222- 228 F7.2 keV Ep-B [10.4/8499] Derived BAND peak energy
230- 236 F7.2 keV E_Ep-B [0.08/2007] Upper uncertainty in Ep-B
238- 244 F7.2 keV e_Ep-B [0.4/4879] Lower uncertainty in Ep-B
246- 252 E7.2 mW/m2 F-B [4.2e-9/0.96]? Derived BAND energy
flux; erg/s/cm2 (1)
254- 262 E9.2 mW/m2 E_F-B [6.2e-8/87]? Upper uncertainty in F-B
(1)
264- 271 E8.2 mW/m2 e_F-B [9.4e-10/8.5e-6]? Lower uncertainty
in F-B (1)
273- 286 F14.2 --- DeltaDIC [-145665983/3843] Difference in
deviance information criterion
between CPL and BAND
288- 295 F8.2 --- PDIC [-1123/3] Effective number of CPL
parameters
297- 309 F13.2 --- PDIC-B [-145665980/4] Effective number of
BAND parameters
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Note (1): A blank means that a reliable value of the flux could not be computed
due to large errors in the fitted parameters.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 31-Mar-2021