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

Yoshiaki Hyodo(1) Masahiro Tsujimoto(2,3) Katsuji Koyama(1) Shogo Nishiyama(4) Tetsuya Nagata(5) Itsuki Sakon(6) Hiroshi Murakami(7) and Hironori Matsumoto(1)


(1) Department of Physics, Graduate School of Science, Kyoto University,,Kita-shirakawa Oiwake-cho, Sakyo, Kyoto 606-8502
(2) Department of Astronomy & Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USA
(3) Department of Physics, Rikkyo University, 3-34-1, Nishi-Ikebukuro, Toshima, Tokyo 171-8501
(4) National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588
(5) Department of Astronomy, Graduate School of Science, Kyoto University,,Kita-shirakawa Oiwake-cho, Sakyo, Kyoto 606-8502
(6) Department of Astronomy, School of Science, the University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-0033
(7) Institute of Space and Astronautical Science, 3-1-1, Yoshinodai, Sagamihara, Kanagawa, 229-8510

Paper: PASJ, 60, SP1, 2008 in press

EPrint Server: 0712.0280

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 +/- 0.6 keV 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-K_s=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.

Preprints available from the authors at hyodo@cr.scphys.kyoto-u.ac.jp , or the raw TeX (no figures) if you click here.

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