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arXiv · 1006.5323

White dwarf masses in intermediate polars observed with the Suzaku satellite

Takayuki Yuasa·Kazuhiro Nakazawa·Kazuo Makishima·Kei Saitou·Manabu Ishida·Ken Ebisawa·Hideyuki Mori·Shin'ya Yamada
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Abstract

Context. White dwarfs (WDs) in cataclysmic variables (CVs) are important experimental laboratories where the electron degeneracy is taking place on a macroscopic scale. Magnetic CVs increase in number especially in the hard X-ray band (>10 keV) thanks to sensitive hard X-ray missions. Aims. From X-ray spectroscopy, we estimate the masses of nearby WDs in moderately-magnetized CVs, or Intermediate Polars (IPs). Methods. Using the Suzaku satellite, we aquired wide-band spectra of 17 IPs, covering 3-50 keV. An accretion column model of Suleimanov et al. (2005) and an optically-thin thermal emission code were used to construct a spectral emission model of IPs with resolved Fe emission lines. By simultaneously fitting the Fe line complex and the hard X-ray continuum of individual spectra, the shock temperature and the WD mass were determined with a better accuracy than in previous studies. Results. We determined the WD masses of the 17 IPs with statistical fitting errors of ~0.1-0.2 Msun in many cases. The WD mass of a recently-found IP, IGR J17195-4100, was also estimated for the first time (1.03+0.24-0.22 Msun). The average WD mass of the sample is 0.88 \pm 0.25 Msun. When our results were compared with previous X-ray mass determinations, we found significant deviation in a few systems although the reason of this is unclear. The iron abundance of the accreting gas was also estimated, and confirmed the previously reported sub-solar tendency in all sources with better accuracy.

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Takayuki Yuasa, Kazuhiro Nakazawa, Kazuo Makishima, Kei Saitou, Manabu Ishida, Ken Ebisawa, Hideyuki Mori, Shin'ya Yamada. 2010-07-08. White dwarf masses in intermediate polars observed with the Suzaku satellite. https://doi.org/10.1051/0004-6361%2F201014542

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