J/ApJS/254/35 Fermi GBM GRBs with multiple pulses (Li+, 2021)
Bayesian time-resolved spectroscopy of multipulse GRBs: variations of emission
properties among pulses.
Li L., Ryde F., Pe'er A., Yu H.-F., Acuner Z.
<Astrophys. J. Suppl. Ser., 254, 35-35 (2021)>
=2021ApJS..254...35L 2021ApJS..254...35L (SIMBAD/NED BibCode)
ADC_Keywords: GRB
Keywords: Gamma-ray bursts; Astronomy data analysis
Abstract:
Gamma-ray bursts (GRBs) are highly variable and exhibit strong
spectral evolution. In particular, the emission properties vary from
pulse to pulse in multipulse bursts. Here we present a time-resolved
Bayesian spectral analysis of a compilation of GRB pulses observed by
the Fermi/Gamma-ray Burst Monitor. The pulses are selected to have at
least four time bins with a high statistical significance, which
ensures that the spectral fits are well determined and spectral
correlations can be established. The sample consists of 39 bursts,
117 pulses, and 1228 spectra. We confirm the general trend that pulses
become softer over time, with mainly the low-energy power-law index
α becoming smaller. A few exceptions to this trend exist, with
the hardest pulse occurring at late times. The first pulse in a burst
is clearly different from the later pulses; three-fourths of them
violate the synchrotron line of death, while around half of them
significantly prefer photospheric emission. These fractions decrease
for subsequent pulses. We also find that in two-thirds of the pulses,
the spectral parameters (α and peak energy) track the
light-curve variations. This is a larger fraction compared to what is
found in previous samples. In conclusion, emission compatible with the
GRB photosphere is typically found close to the trigger time, while
the chance of detecting synchrotron emission is greatest at late
times. This allows for the coexistence of emission mechanisms at late
times.
Description:
We use data obtained by the Fermi Gamma-ray Space Telescope, which was
launched in 2008, and carries two instruments: the GBM and the Large
Area Telescope (LAT). Together, they cover an energy range from a few
keV to a few hundred GeV. By 2019 June, Fermi had completed 11yr of
operation, and at least 2388 gamma-ray bursts (GRBs) had been observed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 103 39 Global properties of the sample
tableb1.dat 226 945 *Time-resolved spectral fits
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Note on tableb1.dat: The typically used functions are the Band function, which
is a broken power-law function, and the cutoff power-law (CPL)
function (Band+ 1993ApJ...413..281B 1993ApJ...413..281B & Gruber+ 2014ApJS..211...12G 2014ApJS..211...12G).
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See also:
J/ApJS/166/298 : Spectral cat. of bright BATSE gamma-ray bursts (Kaneko+, 2006)
J/ApJ/720/1146 : Spectral analysis of GRBs (Lu+, 2010)
J/ApJ/740/104 : BATSE GRB pulse catalog - preliminary data (Hakkila+, 2011)
J/ApJ/756/112 : Fermi/GBM GRB time-resolved spectral analysis (Lu+, 2012)
J/MNRAS/454/L31 : GRB prompt emission fitted with DREAM (Ahlgren+, 2015)
J/A+A/573/A81 : Spectral properties of energetic GRBs (Yu+, 2015)
J/A+A/588/A135 : Fermi/GBM GRB time-resolved spectral catalog (Yu+, 2016)
J/ApJ/855/101 : BATSE TTE GRB pulse catalog (Hakkila+, 2018)
J/ApJ/880/76 : 6 GRBs with Swift XRT and Fermi GBM obs. (Ahlgren+, 2019)
J/ApJ/886/20 : Bayesian time-resolved spectra of Fermi GBM pulses (Yu+, 2019)
J/ApJ/893/46 : The 4th Fermi-GBM GRB catalog: 10 years (von Kienlin+, 2020)
http://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html : Fermi GBM cat.
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 Fermi burst ID (<Fermi bnYYMMDDddd> in Simbad)
11- 16 F6.4 --- z [0.42/2.73]? Redshift
18- 24 F7.3 s T90 [3/449.5] Observed duration t90
26- 30 F5.3 s e_T90 [0.09/6.7] T90 uncertainty
32- 41 A10 --- Det Used detectors (1)
43- 55 A13 --- delT Selected source interval
57- 92 A36 --- delTbkg Background intervals
94- 96 I3 --- Tot [15/110] Number of total BBlock time bins
(S≥20)
98- 99 I2 --- Eff [9/81] Number of used BBlock time bins (S≥20)
101 I1 --- Ntot [2/6] Number of total pulses for each burst
103 I1 --- Nuse [2/5] Number of used pulses for each burst
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Note (1): The detector in parentheses is the brightest one, used for
the BBlocks and background determinations.
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [GRB]
5- 13 I09 --- Fermi Fermi burst ID (1)
15 I1 --- Pulse [1/6] Pulse number
17- 23 F7.3 s BinStart [-0.92/215.1] Start time of the
BBlocks time bin
25- 31 F7.3 s BinStop [0.17/216] Stop time of the BBlocks
time bin
33- 38 F6.2 --- S [15.5/261.5] Significance S of the
time bin
40- 43 F4.2 --- CPL-K [0/6.15] CPL model: normalisation
45- 48 F4.2 --- e_CPL-K [0/0.96] Upper uncertainty on CPL-K
50- 53 F4.2 --- E_CPL-K [0/0.9] Lower uncertainty on CPL-K
55- 59 F5.2 --- CPL-a [-1.97/0.76] CPL model: low-energy
power-law index α
61- 64 F4.2 --- e_CPL-a [0.01/0.33] Upper uncertainty on CPL-a
66- 69 F4.2 --- E_CPL-a [0.01/0.33] Lower uncertainty on CPL-a
71- 74 I4 keV CPL-Ec [11/4977] CPL model: cut-off energy
76- 79 I4 keV e_CPL-Ec [1/2426] Upper uncertainty on CPL-Ec
81- 84 I4 keV E_CPL-Ec [1/2353] Lower uncertainty on CPL-Ec
86- 89 I4 keV CPL-Ep [3/4891] CPL model: peak energy (2)
91- 94 I4 keV e_CPL-Ep [1/1736] Upper uncertainty on CPL-Ep
96- 99 I4 keV E_CPL-Ep [1/1711] Lower uncertainty on CPL-Ep
101- 106 F6.2 10-6mW/m2 CPL-nuFnu [0.24/195.6] CPL model: (νFnu)
energy flux, in erg/s/cm2 units
108- 112 F5.2 10-6mW/m2 e_CPL-nuFnu [0.03/36.1] Upper uncertainty on
CPL-nuFnu
114- 118 F5.2 10-6mW/m2 E_CPL-nuFnu [0.02/22.5] Lower uncertainty on
CPL-nuFnu
120- 123 F4.2 --- Band-K [0/6.52] Band model: normalisation
125- 129 F5.2 --- e_Band-K [-0.01/1.95] Upper uncertainty on
Band-K
131- 134 F4.2 --- E_Band-K [0/1.74] Lower uncertainty on Band-K
136- 140 F5.2 --- Band-a [-1.94/0.93] Band model: low-energy
power-law index α
142- 146 F5.2 --- e_Band-a [-0/0.58] Upper uncertainty on Band-a
148- 151 F4.2 --- E_Band-a [0.01/0.75] Lower uncertainty on
Band-a
153- 157 F5.2 --- Band-B [-7.7/-1.86] Band model: high-energy
power-law index Β
159- 162 F4.2 --- e_Band-B [0.01/3.2] Upper uncertainty on Band-B
164- 167 F4.2 --- E_Band-B [0.01/3.5] Lower uncertainty on Band-B
169- 174 F6.1 keV Band-Ep [9/4582] Band model: peak energy Ep
176- 181 F6.1 keV e_Band-Ep [0.3/1167] Upper uncertainty on
Band-Ep
183- 188 F6.1 keV E_Band-Ep [0.3/1044] Lower uncertainty on
Band-Ep
190- 195 F6.2 10-6mW/m2 Band-nuFnu [0.29/232.7] Band model: (νFnu)
energy flux, in erg/s/cm2 units
197- 201 F5.2 10-6mW/m2 e_Band-nuFnu [0.04/42] Upper uncertainty on
Band-nuFnu
203- 207 F5.2 10-6mW/m2 E_Band-nuFnu [0.04/22] Lower uncertainty on
Band-nuFnu
209- 214 F6.1 --- dDIC [-261/24.3] Difference,
DICBand-DICCPL (3)
216- 220 F5.1 --- pCPL [-57/3.1] Effective number of
parameters (pDIC) for the CPL
222- 226 F5.1 --- pBand [-57.8/4] Effective number of
parameters (pDIC) for the Band model
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Note (1): GRB 120728484 is a misprint for 120728434; corrected at CDS.
Note (2): The peak energy Ep=(2+α)*Ec in the N2N(E) or νFnu spectrum
Note (3): Difference in the Deviance Information Criterion (DIC) for the
CPL and the Band model. DIC is defined as:
DIC=-2log[p(data|θ)]+2pDIC, where θ is the posterior
mean of the parameters, and pDIC is a term to penalize the more
complex model for overfitting. See Section 2.6.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Sep-2021