MAXI GSC detection of a soft X-ray transient : XRF 150826A / MAXI J1501-026

ATel #7954; S. Nakahira (JAXA), K. Yamaoka (Nagoya U.), M. Nakajima (Nihon U.), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.), H. Negoro, M. Nakajima, T. Masumitsu, K. Tanaka (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.), M. Yamauchi, D. Itoh (Miyazaki U.), M. Morii (ISM) report on behalf of the MAXI team
on 26 Aug 2015; 18:01 UT
Credential Certification: Satoshi NAKAHIRA (nakahira@crab.riken.jp)

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MAXI/GSC triggered a bright uncatalogued X-ray transient source at UT 2015-08-26T15:40:57.
The source is extremely soft and most of the flux is emitted below 4 keV. Since usual PSF fitting method did not work due to the softness of this source, we just calculated the centroid position at
(R.A., Dec.) = (225.368, -2.603) (J2000)

By fitting the spectrum with a blackbody, we obtained a temperature of 0.53 ± 0.07 keV. The 2-4 keV X-ray flux of the transient source was 440 mCrab.
There was no significant detection at the transit location in the previous and the next orbit (92 min before and after the detection) with an upper limit of 20 mCrab.
Swift ToO observation has been approved and planned.
Follow-up observations are strongly encouraged.