MAXI/GSC discovery of a new soft X-ray transient MAXI J1828-249
S. Nakahira, H. Tomida (JAXA), H. Negoro (Nihon U.),  M. Morii, T. Mihara (RIKEN),  S. Ueno, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), M. Sugizaki, M. Serino, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),  N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech),  A. Yoshida, T. Sakamoto, Y. Nakano (AGU),  H. Tsunemi, M. Sasaki (Osaka U.),  M. Nakajima, H. Sakakibara, K. Fukushima, T. Onodera, K. Suzuki (Nihon U.), Y. Ueda, M. Shidatsu, T. Kawamuro (Kyoto U.),  Y. Tsuboi, M. Higa (Chuo U.),  M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.), K. Yamaoka (Nagoya U.)  report on behalf of the MAXI team
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source near GS 1826-238 at UT 2013-10-15T21:55:19. We tentatively name the source MAXI J1828-249. We obtain the source position at (R.A., Dec) = (277.118 deg, -24.906 deg) = (18:28:28, -24:54:22) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.32 deg and 0.21 deg, respectively. The roll angle of long axis from the north direction is 36 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged from 15 Oct 2013 12:00UT to 24:00 UT was 93 +/- 9 mCrab (4-10keV, 1 sigma error). The spectrum is quite soft implying a soft state of a black hole binary. Follow-up observations are strongly encouraged to reveal the nature of the source.
x-ray,binary,black hole,neutron star,nova,star,transient