Discovery of the soft X-ray transient MAXI J0158-744
Abstract
MAXI(Monitor of All-sky X-ray Image) is the X-ray all-sky monitor in operation now. MAXI-GSC and SSC is sensitive in the 2-30 keV and 0.5-12 keV band, respectively. On November 11, 2011 (UT), MAXI-GSC discovered a new X-ray transient, MAXI J0158-744 on the outskirts of SMC. Its X-ray spectrum was very soft (below about 5 keV). MAXI-GSC detected it at the first one scan(T0), and MAXI-SSC successively detected it twice, at 200 and 1300 sec after the T0. The luminosity at the MAXI detection was bright (6.4 x 10^{38} erg s^{-1} at d = 61.3 kpc). By the Swift follow-up observation, its X-ray and optical counterparts are found. The Swift-XRT spectra were modeled by blackbody with a temperature less than about 100 eV, which is similar to that of the super soft source (SSS) phase of classical novae. In the spectrum of the second MAXI-SSC scan, we detected an emission line of He-like neon and possibly those of sodium and aluminium in the same ionization state. It suggests that the emission during the first a few 10^{3} sec were thin-thermal emissions produced by the shock of the nova explosion. From the Swift-UVOT spectrum, we infer that the optical counterpart is a post-AGB star. The line emissions of the rare elements detected by MAXI-SSC also support this scenario, suggesting that they are the outcome of the peculiar nucleosynthesis during the AGB phase of the star evolution.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39.1278M