Discovery of a broad O VIII Ly alpha line in the ultracompact X-ray binary 4U 1543-624

作者：Madej O K^*; Jonker P G

来源：Monthly Notices of the Royal Astronomical Society, 2011, 412(1): L11-L15.

DOI：10.1111/j.1745-3933.2010.00989.x

• accretion, accretion discs
• X-rays: binaries
• X-rays: individual: 4U 1543-624

We report the discovery of a broad emission feature at similar to 0.7 keV in the spectra of the ultra-compact X-ray binary 4U 1543-624, obtained with the high-resolution spectrographs of the XMM-Newton and Chandra satellites. We confirm the presence of the feature in the broadband MOS2 spectrum of the source. As suggested before in the literature, the donor star in this source is a CO or ONe white dwarf, which transfers oxygen-rich material to the accretor, conceivably a neutron star. The X-rays reprocessed in this oxygen-rich accretion disc could give a reflection spectrum with O VIII Ly alpha as the most prominent emission line. Apart from the feature at similar to 0.7 keV, we confirm the possible presence of a weak emission feature at similar to 6.6 keV, which was reported in the literature for this data set. We interpret the feature at similar to 0.7 and similar to 6.6 keV as O VIII Ly alpha and Fe K alpha emission, respectively, caused by X-rays reflected off the accretion disc in the strong gravitational field close to the accretor.

• 出版日期2011-3