MAXI observations of GRBs
Abstract
Monitor of all-sky image (MAXI) Gas Slit Camera (GSC) detects gamma-ray bursts (GRBs) including the bursts with soft spectra, such as X-ray flashes (XRFs). MAXI/GSC is sensitive to the energy range from 2 to 30 keV. This energy range is lower than other currently operating instruments which is capable of detecting GRBs. Since the beginning of the MAXI operation on August 15, 2009, GSC observed 35 GRBs up to the middle of 2013. One third of them are also observed by other satellites. The rest of them show a trend to have soft spectra and low fluxes. Because of the contribution of those XRFs, the MAXI GRB rate is about three times higher than those expected from the BATSE log N - log P distribution. When we compare it to the observational results of the Wide-field X-ray Monitor on the High Energy Transient Explorer 2, which covers the the same energy range to that of MAXI/GSC, we find a possibility that many of MAXI bursts are XRFs with Epeak lower than 20 keV. We discuss the source of soft GRBs observed only by MAXI. The MAXI log N - log S distribution suggests that the MAXI XRFs distribute in closer distance than hard GRBs. Since the distributions of the hardness of galactic stellar flares and X-ray bursts overlap with those of MAXI GRBs, we discuss a possibility of a confusion of those galactic transients with the MAXI GRB samples.
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Cite
@article{arxiv.1406.3912,
title = {MAXI observations of GRBs},
author = {Motoko Serino and Takanori Sakamoto and Nobuyuki Kawai and Atsumasa Yoshida and Masanori Ohno and Yuji Ogawa and Yasunori Nishimura and Kosuke Fukushima and Masaya Higa and Kazuto Ishikawa and Masaki Ishikawa and Taiki Kawamuro and Masashi Kimura and Masaru Matsuoka and Tatehiro Mihara and Mikio Morii and Yujin E. Nakagawa and Satoshi Nakahira and Motoki Nakajima and Yuki Nakano and Hitoshi Negoro and Takuya Onodera and Masayuki Sasaki and Megumi Shidatsu and Juri Sugimoto and Mutsumi Sugizaki and Fumitoshi Suwa and Kazuhiko Suzuki and Yutaro Tachibana and Toshihiro Takagi and Takahiro Toizumi and Hiroshi Tomida and Yohko Tsuboi and Hiroshi Tsunemi and Yoshihiro Ueda and Shiro Ueno and Ryuichi Usui and Hisaki Yamada and Takayuki Yamamoto and Kazutaka Yamaoka and Makoto Yamauchi and Koshiro Yoshidome and Taketoshi Yoshii},
journal= {arXiv preprint arXiv:1406.3912},
year = {2015}
}
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12 figures