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ID 30783
file
creator
Uehara, Takeshi
Kawabata, Koji S
Yamazaki, Ryo
Arai, Akira
Sasada, Mahito
Ohsugi, Takashi
Yamashita, Takuya
Ohno, Masanori
Sato, Goro
Sato, Shuji
Kino, Masaru
subject
gamma-ray burst
individual
GRB 071112C – gamma-ray burst
individual
GRB 080506
NDC
Astronomy. Space sciences
abstract
Aims. We investigate the origin of short X-ray flares which are occasionally observed in early stages of afterglows of gamma-ray bursts (GRBs).

Methods. We observed two Swift events, GRB 071112C and GRB 080506, before the start of X-ray flares in the optical and near-infrared (NIR) bands with the 1.5-m Kanata telescope. In conjunction with published X-ray and optical data, we analyzed densely sampled light curves of the early afterglows and spectral energy distributions (SEDs) in the NIR-X-ray ranges.

Results. We found that the SEDs had a break between the optical and X-ray bands in the normal decay phases of both GRBs regardless of the model for the correction of the interstellar extinction in host galaxies of GRBs. In the X-ray flares, X-ray flux increased by 3 and 15 times in the case of GRB 071112C and 080506, respectively, and the X-ray spectra became harder than those in the normal decay phases. No significant variation in the optical-NIR range was detected together with the X-ray flares.

Conclusions. These results suggest that the X-ray flares were associated with either late internal shocks or external shocks from two-component jets.
journal title
Astronomy & Astrophysics
volume
Volume 519
start page
A56-1
end page
A56-9
date of issued
2010-09
publisher
EDP Sciences S A
issn
0004-6361
ncid
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
Copyright (c) 2010 The European Southern Observatory
relation url
department
Graduate School of Science