MAXI/GSC detection of a new X-ray transient MAXI J1807-228
ATel #4335; H. Negoro (Nihon U.), S. Nakahira (JAXA), M. Morii (Tokyo Tech), S. Ueno, H. Tomida, M. Ishikawa (JAXA), T. Mihara, M. Serino, M. Sugizaki, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, R. Usui, K. Ishikawa (Tokyo Tech), M. Nakajima, M. Asada, N. Serita (Nihon U.), A. Yoshida (AGU), H. Tsunemi, M. Kimura (Osaka U.), Y. Ueda, K. Hiroi, M. Shidatsu, R. Sato (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.) M. Yamauchi, Y. Nishimura, T. Hanayama, K. Yoshidome (Miyazaki U.), K. Yamaoka (Waseda U.) report on behalf of the MAXI team
on 25 Aug 2012; 10:09 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)
Subjects: X-ray, Black Hole, Cataclysmic Variable, Neutron Star, Transient
On 2012 August 24, the MAXI/GSC detects enhanced X-ray emission at a position:
(R.A., Dec) = (271.96 deg, -22.80 deg) = (18 07 50, -22 48 00) (J2000)
with a statistical uncertainty of 0.2 deg at the 90% confidence limit and
an additional systematic uncertainty of 0.1 deg (90% containment radius).
There is no bright known X-ray source within the error circle, and
we tentatively name the source MAXI J1807-228.
The source has been recognized on X-ray scan images since the afternoon of
August 24, and total source counts in the 2-10 keV band during 9 scan transits
from August 24 at 14:14 UT to August 25 at 02:38 is 38.8+-8.0 counts,
corresponding to approximately 40 mCrab. The data also show that the source has
a relatively soft energy spectrum.
The source flux does not change significantly during the period, and
already tends to decrease.
Follow-up observations are encouraged to reveal the nature of this transient.
The latest light curves and images of MAXI J1807-228 by MAXI/GSC will be
placed at the following URL: http://maxi.riken.jp/top/index.php?cid=1&jname=J1807-228
MAXI home page
