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arXiv · 1006.0785

Infrared/optical - X-ray simultaneous observations of X-ray flares in GRB 071112C and GRB 080506

T. Uehara·M. Uemura·K. S. Kawabata·Y. Fukazawa·R. Yamazaki·A. Arai·M. Sasada·T. Ohsugi·T. Mizuno·H. Takahashi·H. Katagiri·T. Yamashita·M. Ohno·G. Sato·S. Sato·M. Kino
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Abstract

We investigate the origin of short X-ray flares which are occasionally observed in early stages of afterglows of gamma-ray bursts (GRBs). We observed two 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. 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. These results suggest that the X-ray flares were associated with either late internal shocks or external shocks from two-component jets.

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T. Uehara, M. Uemura, K. S. Kawabata, Y. Fukazawa, R. Yamazaki, A. Arai, M. Sasada, T. Ohsugi, T. Mizuno, H. Takahashi, H. Katagiri, T. Yamashita, M. Ohno, G. Sato, S. Sato, M. Kino. 2010-06-04. Infrared/optical - X-ray simultaneous observations of X-ray flares in GRB 071112C and GRB 080506. https://doi.org/10.1051/0004-6361/201014272

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