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

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.

Original languageEnglish
Article numberA56
JournalAstronomy and Astrophysics
Volume519
Issue number7
DOIs
Publication statusPublished - 2010 Sep 14

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Keywords

  • gamma-ray burst: individual: GRB 071112C
  • gamma-ray burst: individual: GRB 080506

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Uehara, T., Uemura, M., Kawabata, K. S., Fukazawa, Y., Yamazaki, R., Arai, A., Sasada, M., Ohsugi, T., Mizuno, T., Takahashi, H., Katagiri, H., Yamashita, T., Ohno, M., Sato, G., Sato, S., & Kino, M. (2010). Infrared/optical - X-ray simultaneous observations of X-ray flares in GRB 071112C and GRB 080506. Astronomy and Astrophysics, 519(7), [A56]. https://doi.org/10.1051/0004-6361/201014272