J/ApJ/826/45 GRB X-ray afterglows light curves analysis (Racusin+, 2016)
A correlation between the intrinsic brightness and average decay rate of
gamma-ray burst X-ray afterglow light curves.
Racusin J.L., Oates S.R., de Pasquale M., Kocevski D.
<Astrophys. J., 826, 45-45 (2016)>
=2016ApJ...826...45R 2016ApJ...826...45R (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays ; Redshifts ; X-ray sources
Keywords: gamma-ray burst: general; X-rays: bursts
Abstract:
We present a correlation between the average temporal decay
(αX,avg,>200s) and early-time luminosity (LX,200s) of X-ray
afterglows of gamma-ray bursts as observed by the Swift X-ray
Telescope. Both quantities are measured relative to a rest-frame time
of 200s after the γ-ray trigger. The luminosity-average decay
correlation does not depend on specific temporal behavior and contains
one scale-independent quantity minimizing the role of selection
effects. This is a complementary correlation to that discovered by
Oates et al. (2012MNRAS.426L..86O 2012MNRAS.426L..86O, 2015MNRAS.453.4121O 2015MNRAS.453.4121O) in the optical
light curves observed by the Swift Ultraviolet Optical Telescope. The
correlation indicates that, on average, more luminous X-ray afterglows
decay faster than less luminous ones, indicating some relative
mechanism for energy dissipation. The X-ray and optical correlations
are entirely consistent once corrections are applied and contamination
is removed. We explore the possible biases introduced by different
light-curve morphologies and observational selection effects, and how
either geometrical effects or intrinsic properties of the central
engine and jet could explain the observed correlation.
Description:
All GRBs discovered with Swift-BAT, with X-ray afterglows detected by
Swift-XRT and measured redshifts, between 2004 December and 2014 March
are included in the analysis. We include only those X-ray afterglows
with at least three light-curve bins (≳60 counts) and T90
measurements are available in the BAT catalogs (Sakamoto+ 2008,
J/ApJS/175/179; 2011, J/ApJS/195/2 and Lien+ 2016, arXiv:1606.01956).
The final sample includes 237 long-duration GRBs (9 short), 47 of
which also appear in the Oates et al. (2012MNRAS.426L..86O 2012MNRAS.426L..86O;
2015MNRAS.453.4121O 2015MNRAS.453.4121O) sample for the UVOT correlation (sample only
extends through 2010). The redshift measurements come from a
convolution of databases and the literature and are listed in Table 1.
All light curves were retrieved from the University of Leicester Swift
XRT Team GRB repository (Evans et al. 2007A&A...469..379E 2007A&A...469..379E; 2009,
J/MNRAS/397/1177). See section 2.2 for further explanations.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 102 247 The properties of the GRBs in our sample
refs.dat 108 174 References
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See also:
J/ApJ/778/128 : GRB-host galaxies photometry (Perley+, 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/ApJ/746/156 : Radio afterglow observations of GRBs (Chandra+, 2012)
J/MNRAS/418/2202 : Analysis of γ-ray bursts (Dainotti+, 2011)
J/ApJS/195/2 : The second Swift BAT GRB catalog (BAT2) (Sakamoto+, 2011)
J/ApJ/727/73 : Composite spectrum of GRB afterglows (Christensen+, 2011)
J/ApJ/720/1513 : The afterglows of Swift-era GRBs. I. (Kann+, 2010)
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
J/ApJ/701/824 : Afterglows of short & long-duration GRBs (Nysewander+, 2009)
J/ApJS/175/179 : The BAT1 gamma-ray burst catalog (Sakamoto+, 2008)
J/A+A/455/813 : BeppoSAX cat. of GRB X-ray afterglows (De Pasquale+, 2006)
http://www.astro.caltech.edu/grbhosts/redshifts.html : Preliminary Keck GRB
host project spectroscopy catalog
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [GRB]
4- 10 A7 --- GRB Gamma-ray burst identifier
12- 15 F4.2 --- z [0.03/9.2] Redshift
17- 51 A35 --- r_z Reference for z (see refs.dat file)
53- 57 F5.1 s T90 [0.2/734] Time in which 90% of prompt
fluence is emitted
59- 62 F4.2 --- aX [0.2/3.1] Average temporal decay
after 200s (αX,avg,>200s)
64- 67 F4.2 --- E_aX [0.01/2.3] Upper uncertainty in aX
69- 72 F4.2 --- e_aX Lower 1σ uncertainty in aX
74- 80 E7.2 10-7J/cm2/Hz LX Early time X-ray luminosity at 1keV (1)
82- 88 E7.2 10-7J/cm2/Hz E_LX Upper 1σ uncertainty in LX
90- 96 E7.2 10-7J/cm2/Hz e_LX Lower 1σ uncertainty in LX
98 A1 --- SDC [ny] Steep Decay Contaminated flag
100 A1 --- Pl [ny] Plateau flag
102 A1 --- Fl [ny] Flares flag
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Note (1): In units of erg/cm2/Hz.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 35 A35 --- Ref Reference text (Author and year; as in table 1)
37- 55 A19 --- BibCode Bibcode of the reference if any
57-108 A52 --- Comm Comment
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Sep-2016