TY - JOUR
T1 - Infrared/optical - X-ray simultaneous observations of X-ray flares in GRB 071112C and GRB 080506
AU - Uehara, T.
AU - Uemura, M.
AU - Kawabata, K. S.
AU - Fukazawa, Y.
AU - Yamazaki, R.
AU - Arai, A.
AU - Sasada, M.
AU - Ohsugi, T.
AU - Mizuno, T.
AU - Takahashi, H.
AU - Katagiri, H.
AU - Yamashita, T.
AU - Ohno, M.
AU - Sato, G.
AU - Sato, S.
AU - Kino, M.
PY - 2010/9/14
Y1 - 2010/9/14
N2 - 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.
AB - 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.
KW - gamma-ray burst: individual: GRB 071112C
KW - gamma-ray burst: individual: GRB 080506
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U2 - 10.1051/0004-6361/201014272
DO - 10.1051/0004-6361/201014272
M3 - Article
AN - SCOPUS:77956678329
SN - 0004-6361
VL - 519
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
IS - 7
M1 - A56
ER -