Suzaku X-Ray Spectroscopy of a Peculiar Hot Star in the Galactic Center Region

TL;DR

This study analyzes a peculiar X-ray source in the Galactic center, revealing it as a likely Wolf-Rayet binary with high plasma temperature and luminosity, based on Suzaku and XMM-Newton data.

Contribution

First detailed X-ray spectral analysis of a peculiar source in the Galactic center, identifying it as a Wolf-Rayet binary candidate.

Findings

Detected intense FeXXV 6.7 keV line with ~1 keV equivalent width.

Spectrum well described by a heavily absorbed thermal plasma model at ~3.8 keV.

Infrared SED suggests a WC-type Wolf-Rayet star.

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 FeXXV 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 (~2x10^{23}cm^{-2}) thin thermal plasma model with a temperature of 3.8+/-0.6 keV and a luminosity of ~3x10^{34} 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.