J/ApJ/949/110 Pulses from Fermi-GBM gamma-ray bursts (Tak+, 2023)
Temporal and spectral evolution of gamma-ray burst broad pulses: identification
of high-latitude emission in the prompt emission.
Tak D., Uhm Z.L., Racusin J., Zhang B., Guiriec S., Kocevski D.,
Zhang B.-B., McEnery J.
<Astrophys. J., 949, 110 (2023)>
=2023ApJ...949..110T 2023ApJ...949..110T
ADC_Keywords: GRB
Keywords: Gamma-ray bursts ; Relativistic jets
Abstract:
We perform a detailed analysis of broad pulses in bright gamma-ray
bursts (GRBs) to understand the evolution of GRB broad pulses. Using
the temporal and spectral properties, we test the high-latitude
emission (HLE) scenario in the decaying phase of broad pulses. The HLE
originates from the curvature effect of a relativistic spherical jet,
where higher-latitude photons are delayed and softer than the
observer's line-of-sight emission. The signature of HLE has not yet
been identified undisputedly during the prompt emission of GRBs. The
HLE theory predicts a specific relation, Fν,Ep∝Ep2,
between the peak energy Ep in νFν spectra and the spectral flux
Fν measured at Ep, Fν,Ep. We search for evidence of this
relation in 2157 GRBs detected by the Gamma-ray Burst Monitor on board
the Fermi Gamma-ray Space Telescope from 2008 to 2017. After imposing
unbiased selection criteria in order to minimize contamination in a
signal by background and overlaps of pulses, we build a sample of
32 broad pulses in 32 GRBs. We perform a time-resolved spectral
analysis on each of these 32 broad pulses and find that the evolution
of 18 pulses (56%) is clearly consistent with the HLE relation. For
the 18 broad pulses, the exponent δ in the relation of
Fν,Ep∝Epδ is distributed as a Gaussian function
with a median and width of 1.99 and 0.34, respectively. This result
provides a constraint on the emission radius of GRBs with the HLE
signature.
Description:
Our initial sample consists of 2157 gamma-ray bursts (GRBs) listed in
the Fermi-GBM catalog observed in 2008-2017.
In order to study the temporal and spectral features of GRB broad
pulses, we perform a time-resolved analysis of a sufficient number of
bins. Since only bright GRBs can provide well-constrained parameters
in the time-resolved spectral analysis, we select GRBs based on energy
fluence and peak flux in the energy band from 10keV to 1MeV, i.e., the
energy fluence and peak flux thresholds are 2.5x10-5erg/cm2 and
1.8x10-6erg/cm2/s, respectively.
After the selection procedure, our final sample consists of 32 bright
broad pulses from 32 GRBs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 66 32 Spectral analysis parameters for selected GRBs
table2.dat 52 175 Parameters related to selection criteria
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See also:
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/ApJS/211/13 : The second Fermi/GBM GRB catalog (4yr) (von Kienlin+, 2014)
J/A+A/588/A135 : Fermi/GBM GRB time-resolved spectral catalog (Yu+, 2016)
J/ApJ/865/153 : Analysis of Fermi GRB data. IV. Spectral lags (Lu+, 2018)
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 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- 11 A11 --- Name GRB name (GRB YYMMDDA) (1)
13- 18 F6.3 s PStart [-0.82/72.8] Pulse start
20- 25 F6.3 s AStart [0.17/78] Analysis start
27- 33 F7.3 s AEnd [5.17/186] Analysis end
35- 36 I2 --- Nbins [9/29] Number of bins
38- 42 A5 --- HLE High-latitude emission (HLE) evidence
44- 46 F3.1 --- PLInd [1.7/2.4]? PL index
48- 50 F3.1 --- e_PLInd [0.2/1.4]? PLInd uncertainty
52- 54 F3.1 --- Chi2 [0.1/1.8]? χ2ν
56- 66 A11 --- Fermi Trigger name as in Table 2; column added by CDS
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Note (1): GRB 150213B was a misprint for GRB 150213A; corrected at CDS.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Fermi Trigger name
13- 17 F5.1 10-8J/m2 Flu [2.5/141.2] Fluence; 10-5erg/cm2
19- 23 F5.1 10-6mW/m2 FluxPk [1.8/176.0] Peak flux; 10-6erg/cm2/s
25- 27 I3 % FluPer [9/100] Percentage fluence
29- 32 F4.1 s tRise [0.2/61.0] Rise time
34- 37 F4.1 s tDecay [0.3/83.2] Decay time
39- 42 F4.1 s tBumps [0.0/60.0] Bumps time
44- 44 A1 --- C1 First criteria (1)
46- 46 A1 --- C2 Second criteria (1)
48- 48 A1 --- C3 Third criteria (1)
50- 50 A1 --- C4 Fourth criteria (1)
52- 52 A1 --- Final Final results ("O"=32 occurrences)
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Note (1): Details of criteria are in the Section 2. Code as follows:
T = yellow flag; 70%≤Sp<90%
X = red flag; Sp<70%
where Sp is the fluence of the brightest pulse in a GRB.
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Acknowledgements:
Donggeun Tak [donggeun.tak at gmail]
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Jul-2025