MAXI/GSC detection of a hard-to-soft transition of NS-LMXB GS 1826-238
ATel #6250; S. Nakahira (JAXA), T. Mihara, M. Sugizaki, M. Serino, M. Morii, J. Sugimoto, T. Takagi, A. Yoshikawa, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), H. Negoro, M. Nakajima, K. Fukushima, T. Onodera, K. Suzuki, M. Fujita, T. Namba, F. Honda (Nihon U.), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, D. Uchida (Osaka U.), Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.), A. Kawagoe, Y. Tsuboi (Chuo U.), M. Yamauchi, Y. Morooka (Miyazaki U.), K. Yamaoka (Nagoya U.), report on behalf of the MAXI team
on 20 Jun 2014; 04:50 UT
Credential Certification: Satoshi NAKAHIRA (nakahira@crab.riken.jp)
Subjects: X-ray, Binary, Neutron Star
Referred to by ATel #: 10117
We report on a hard-to-soft spectral transition of an X-ray burster
GS 1826-238 detected with MAXI/GSC.
This source had been consistently observed in the hard state for more than 25 years
since the discovery in 1988 (Tanaka 1989, Barret et al. 1995, Ubertini et al. 1999, Cocchi et al. 2010),
including the recent five years monitored by MAXI.
On 2014 June 8, the MAXI/GSC hardness ratio (7-20keV / 2-7 keV) suddenly decreased
from ~ 0.4 to 0.1.
According to the hardness change,
the 2-10 keV X-ray flux increased from 50 mCrab (before May 2014) to 140 mCrab (15 June 2014),
while the 15-50 keV flux monitored by Swift BAT decreased.
All these results indicate that the source entered into the soft state.
MAXI light curves are in
http://maxi.riken.jp/top/index.php?cid=1&jname=J1829-237
MAXI and BAT light curves and MAXI spectra are in
http://maxi.riken.jp/news/en/?p=1112
Multi-wavelength observations are encouraged.
