Suzaku X-ray spectroscopy of a peculiar hot star in the galactic center region

Abstract

We present the results of a Suzaku study of a bright point-like source in the 6.7 keV intensity map of the Galactic center region. We detected an intense Fe XXV 6.7 keV line with an equivalent width of ∼ 1 keV as well as emission lines of highly ionized Ar and Ca from a spectrum obtained by the X-ray Imaging Spectrometer. The overall spectrum is described very well by a heavily absorbed (∼ 2 × 1023 cm-2) thin thermal plasma model with a temperature of 3.8 ± 0.6keV and a luminosity of ∼ 3 × 1034 erg s_1 (2.0-8.0 keV) at 8 kpc. The absorption, temperature, luminosity, and the 6.7 keV line intensity were confirmed with the archived XMM-Newton data. The source has a very red (J - Ks = 8.2 mag) infrared spectral energy distribution (SED), which was fitted by a blackbody emission of ∼ 1000 K attenuated by a visual extinction of ∼ 31 mag. The high plasma temperature and the large X-ray luminosity are consistent with a wind-wind colliding Wolf-Rayet binary. The similarity of the SED to those of the eponymous Quintuplet cluster members suggests that the source is a WC-type source. © 2008. Astronomical Society of Japan.