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. =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, F_{nu},Ep_{propto}E_p_^2^, between the peak energy Ep in {nu}F{nu} spectra and the spectral flux F{nu} measured at Ep, F_{nu},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 {delta} in the relation of F_{nu},Ep_{propto}Ep^{delta}^ 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^-5^erg/cm^2^ and 1.8x10^-6^erg/cm^2^/s, respectively. After the selection procedure, our final sample consists of 32 bright broad pulses from 32 GRBs. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 66 32 Spectral analysis parameters for selected GRBs table2.dat 52 175 Parameters related to selection criteria -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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]? {chi}^2^_{nu}_ 56- 66 A11 --- Fermi Trigger name as in Table 2; column added by CDS -------------------------------------------------------------------------------- Note (1): GRB 150213B was a misprint for GRB 150213A; corrected at CDS. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 11 A11 --- Fermi Trigger name 13- 17 F5.1 10-8J/m2 Flu [2.5/141.2] Fluence; 10^-5^erg/cm^2^ 19- 23 F5.1 10-6mW/m2 FluxPk [1.8/176.0] Peak flux; 10^-6^erg/cm^2^/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) -------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------------- Acknowledgements: Donggeun Tak [donggeun.tak _at_ gmail] History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Jul-2025