MAXI/GSC observation of 1RXS J180408.9-342058 in outburst

ATel #7008; H. Negoro (Nihon U.), J. Sugimoto, T. Mihara (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), M. Sugizaki, M. Serino, M. Morii, T. Takagi, A. Yoshikawa, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, D. Uchida (Osaka U.), M. Nakajima, K. Fukushima, T. Onodera, K. Suzuki, T. Namba, M. Fujita, F. Honda (Nihon U.), Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, A. Kawagoe (Chuo U.), M. Yamauchi, Y. Morooka, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team:
on 30 Jan 2015; 06:22 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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MAXI/GSC monitors the neutron star binary 1RXS J180408.9-342058 recently detected by Swift/BAT (Krimm et al., ATel. #6997). MAXI/GSC has also detected a gradual increase in 2-20 keV X-rays from the region, positionally consistent with the BAT source position, since 2015 January 20 (MJD 57042). The 2-20 keV count flux on January 20 was 0.039 +/- 0.013 (corresponding to 12 mCrab), and the peak count flux of 0.124 +/- 0.018 (38 mCrab) was observed on January 27 (MJD 57049). MAXI hardly observed the source region during the period from 2015 January 2 (MJD 57024) to January 19 (MJD 57041) because of worse observational conditions.

A GSC spectrum obtained from January 26.751 to 28.282 shows a relatively hard spectrum, which can be represented by a power-law spectrum with the photon index of 1.68 +/- 0.27. The column density of the absorption can not be constrained due to poor statistics.

We note that as Krimm et al. pointed out (ATel. 6997) the nature of the source obtained with MAXI/GSC is difference from that 1RXS J180408.9-342058 that exhibited a burst-only-source like behavior in 2012 (ATel #4050, #4085). MAXI/GSC public data products are available at http://maxi.riken.jp/top/index.php?cid=1&jname=J1804-343 .