J/A+A/707/A392 Spectral fitting of gamma-ray bursts (Zhang+, 2026)
Exploring the central engines of gamma-ray bursts from prompt light curves.
Zhang X., Yi S.-X., Lei W.-H., Liu T., Yang Y.-P., Qin Y., Qu Y.-K.,
Tang Q.-W., Wang F.-Y.
<Astron. Astrophys. 707, A392 (2026)>
=2026A&A...707A.392Z 2026A&A...707A.392Z (SIMBAD/NED BibCode)
ADC_Keywords: GRB ; Redshifts
Keywords: accretion - accretion disks - black hole physics -
gamma-ray burst: general
Abstract:
Hyperaccreting stellar-mass black hole systems are leading candidates
for the central engines of gamma-ray bursts (GRBs). Their jets are
thought to be powered by either the Blandford-Znajek (BZ) process or
neutrino-dominated accretion flows (NDAFs), but discriminating between
these mechanisms remains challenging. To address this, we proposed
using the luminosity decay slope (d) of GRB light curves to
distinguish between the BZ and NDAF mechanisms, thereby linking the
light-curve morphology to the central engine physics. By analysing 85
single-peaked GRBs with fast-rise, exponential-decay (FRED) profiles
observed by Swift/BAT using 64 ms background-subtracted light curves,
we fitted the decay slope (d) with the empirical
Kocevski-Ryde-Liang (KRL) function and compared the results with
theoretical predictions for the BZ (d∼1.67) and the NDAF
(d∼3.7-7.8) mechanisms. We find that the decay slope (d) can
differentiate central engine mechanisms, with 15 GRBs consistent with
the BZ mechanism and 22 supporting the NDAF mechanism. However, most
events exhibit slopes within the range 2<d<4, suggesting a hybrid
of mechanisms, with NDAF being dominant.
Description:
To investigate the differences in light-curve morphology between
NDAF and BZ mechanisms, we performed spectral fitting using the KRL
function and analysed 85 single-pulse GRBs. The results of the
light-curve fits, along with the isotropic gamma-ray energy
(Egamma,iso) and duration (T90), are listed in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 206 85 Fitting parameters of 2004-2025 FRED-individual
pulses in Swift
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- GRB GRB name
8- 9 A2 --- n_GRB [d dd] Note on GRB (1)
12 A1 --- l_T90 Limit flag on T90
13- 18 F6.2 s T90 Duration
20- 23 F4.2 --- z Cosmological redshift
25- 27 A3 --- Model Model (PL or CPL)
29- 32 F4.2 --- alpha Spectral index
34- 39 F6.2 keV Epeak ?=- Peak energy
41- 47 F7.2 10+14W/cm2 Fluence Fluence (in 10-7erg/cm2)
50- 54 F5.2 10+14W/cm2 E_Fluence Fluence upper error (in 10-7erg/cm2)
56- 61 F6.2 10+14W/cm2 e_Fluence Fluence lower error (in 10-7erg/cm2)
63- 69 F7.3 10+45W Egiso Isotropic gamma-ray energy (in 1052erg)
72- 77 F6.4 10+45W E_Egiso Isotropic gamma-ray energy upper error
(in 1052erg)
80- 85 F6.4 10+45W e_Egiso Isotropic gamma-ray energy lower error
(in 1052erg)
86- 91 F6.2 --- T0 T0 (KRL function fitting)
93- 98 F6.2 --- Tstart Tstart (KRL function fitting)
100-105 F6.2 --- Tend Tend (KRL function fitting)
107-112 F6.2 --- Tp Peak time (KRL function fitting)
115-118 F4.2 --- E_Tp Peak time upper error
(KRL function fitting)
121-124 F4.2 --- e_Tp Peak time lower error
(KRL function fitting)
126-132 F7.2 10+43J Lp Peak luninosity (in 1050erg/s)
135-140 F6.2 10+43J E_Lp Peak luninosity upper error
(in 1050erg/s)
142-147 F6.2 10+43J e_Lp Peak luninosity lower error
(in 1050erg/s)
150-154 F5.2 --- r Power-law index for the ride phase
157-160 F4.2 --- E_r Power-law index for the ride phase
upper error
163-166 F4.2 --- e_r Power-law index for the ride phase
lower error
168-172 F5.2 --- d Power-law index for the decay phase
175-178 F4.2 --- E_d Power-law index for the decay phase
upper error
181-184 F4.2 --- e_d Power-law index for the decay phase
lower error
186-192 F7.2 --- chi2 chi2 value
194-197 I4 --- dof Degree of freedom
199-202 F4.2 --- rchi2 Reduced chi2 value
204 A1 --- BZ [V-] BZ fitted model
206 A1 --- NDAF [V-] NDAF fitted model
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Note (1): Nores as follows:
d = estimated redshift
dd = assumed redshift, the typical redshifts are z=2 for long GRBs
and z=0.5 for short GRBs (Song et al., 2015ApJ...815...54S 2015ApJ...815...54S).
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History:
From electronic version of the journal
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Patricia Vannier [CDS] 23-Mar-2026