J/ApJ/828/36 GRB light-curve decay indices with Swift (Del Vecchio+, 2016)
Study of GRB light-curve decay indices in the afterglow phase.
Del Vecchio R., Dainotti M.G., Ostrowski M.
<Astrophys. J., 828, 36-36 (2016)>
=2016ApJ...828...36D 2016ApJ...828...36D (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays
Keywords: distance scale; gamma-ray burst: general
Abstract:
In this work, we study the distribution of temporal power-law decay
indices, α, in the gamma-ray burst (GRB) afterglow phase, fitted
for 176 GRBs (139 long GRBs, 12 short GRBs with extended emission, and
25 X-ray flashes) with known redshifts. These indices are compared
with the temporal decay index, αW, derived with the
light-curve fitting using the Willingale+ (2007ApJ...662.1093W 2007ApJ...662.1093W) model.
This model fitting yields similar distributions of αW to the
fitted α, but for individual bursts a difference can be
significant. Analysis of (α, La) distribution, where La is
the characteristic luminosity at the end of the plateau, reveals only
a weak correlation of these quantities. However, we discovered a
significant regular trend when studying GRB α values along the
Dainotti+ (2013ApJ...774..157D 2013ApJ...774..157D) correlation between La and the end
time of the plateau emission in the rest frame, Ta*, hereafter LT
correlation. We note a systematic variation of the α parameter
distribution with luminosity for any selected Ta*. We analyze this
systematics with respect to the fitted LT correlation line, expecting
that the presented trend may allow us to constrain the GRB physical
models. We also attempted to use the derived correlation of
α(Ta) versus La(Ta) to diminish the luminosity scatter
related to the variations of α along the LT distribution, a step
forward in the effort of standardizing GRBs. A proposed toy model
accounting for this systematics applied to the analyzed GRB
distribution results in a slight increase of the LT correlation
coefficient.
Description:
We analyze the distribution of afterglow light-curve decay indices,
α, for the data set of 176 gamma-ray bursts (GRBs) with known
redshifts, observed by Swift from 2005 January to 2014 July.
The fitted slopes and normalization parameters of the correlations
presented in this paper are derived using the D'Agostini
(2005physics..11182D) method. The ΛCDM cosmology applied here
uses the parameters H0=71km/s/Mpc, ΩΛ=0.73, and
ΩM= 0.27.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 35 172 GRB afterglow decay index fits
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See also:
IX/43 : 1SXPS Swift X-ray telescope point source catalogue (Evans+ 2014)
J/A+A/589/A98 : Swift GRBs power density spectra (Guidorzi+, 2016)
J/ApJS/224/20 : 10yr of Swift/XRT obs. of GRBs (Yi+, 2016)
J/ApJ/800/16 : Swift-XRT long GRB durations (Boer+, 2015)
J/ApJS/209/20 : Swift GRB catalog with X-ray data (Grupe+, 2013)
J/ApJ/774/157 : Swift GRBs with X-ray afterglows and z<9.5 (Dainotti+, 2013)
J/MNRAS/428/729 : GRB Swift X-ray light curves analysis (Margutti+, 2013)
J/MNRAS/418/2202 : Analysis of γ-ray bursts (Dainotti+, 2011)
J/ApJ/731/103 : Redshift catalog for Swift long GRBs (Xiao+, 2011)
J/ApJ/720/1513 : The afterglows of Swift-era GRBs. I. (Kann+, 2010)
J/ApJ/701/824 : Afterglows of short & long-duration GRBs (Nysewander+, 2009)
J/ApJ/690/163 : The first Swift UV-Opt GRB afterglow catalog (Roming+, 2009)
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
http://www.swift.ac.uk/burst_analyser/ : All GRBs observed by Swift LC fluxes
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 identifier (YYMMDDA)
9 A1 --- l_alpha Limit flag on alpha
10- 13 F4.2 --- alpha [0.49/3.41] Fitted decay index
15- 18 F4.2 --- e_alpha [0.01/0.4] Uncertainty in alpha
20- 23 F4.2 [s] logT1 [1.9/6] Log of starting time of fit
25- 28 F4.2 [s] logT2 [3/7.1] Log of ending time of fit
30- 35 A6 --- Type GRB type (L=long; S=short and XRF=X-ray flashes)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Dec-2016