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arXiv 2101.03059astro-ph.SRastro-ph.HE
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具有简并施主的食激变变星OV Bootis和SDSS J103533 .02+055158.3的X射线和紫外线观测

X-ray and ultraviolet observations of the eclipsing cataclysmic variables OV Bootis and SDSS J103533.02+055158.3 with degenerate donors

Axel Schwope, Hauke Worpel, Iris Traulsen

摘要:

大多数激变变星被预测为后周期最小系统,具有退化的施主星,即周期保镖。然而,由于其内在的模糊性,迄今为止只有少数这些系统被安全地识别出来。我们想研究两个食周期弹跳者OV Bootis和SDSS J103533.02+055158.3的X射线特性,这两个弹跳者是因为离地球很近而被选中进行这项研究的。我们获得了这两个天体的XMM-牛顿相位分辨X射线和紫外观测,用于光谱和时间分析。由于最近的一次矮新星爆发,OV Boo在X射线和紫外线波长上比SDSS J103533.02+055158.3亮得多,因此可以对日食进行一些详细的研究。一个更新的日食星历表被推导出来。X射线被证明起源于白矮星附近,即边界层,其吸收影响其光谱。在SDSS J103533.02+055158.3中没有吸收,尽管在相同的倾角下观察到,表明椎间盘和椎间盘边缘的形状不同。这两个天体的白矮星温度都被重新测定:OV Boo中的白矮星在矮新星爆发后5个月仍然很热(23,000 K),SDSS J103533.02+055158.3中的白矮星比之前假设的更热(Teff = 11,500 K)。到目前为止,在X射线中研究的所有三个具有简并施主的激变变星,包括SDSS J121209.31+013627.7,都在X射线中被清楚地发现,并揭示了质量吸积率dot(M)>= 8 x 10^(-15)Msun/ yr。如果它们的X射线行为代表了周期跳跃者的亚群,那么使用eROSITA进行的全天空X射线巡天以及全面的后续行动将发现足够数量的新天体,以解决有关后期激变变星演化的剩余问题。

英文摘要:

The majority of cataclysmic variables are predicted to be post-period minimum systems with degenerate donor stars, the period bouncers. Owing to their intrinsic faintness, however, only a handful of these systems have so far been securely identified. We want to study the X-ray properties of two eclipsing period bouncers, OV Bootis and SDSS J103533.02+055158.3, that were selected for this study due to their proximity to Earth. We have obtained XMM-Newton phase-resolved X-ray and ultraviolet observations of the two objects for spectral and timing analysis. Owing to a recent dwarf nova outburst OV Boo was much brighter than SDSS J103533.02+055158.3 at X-ray and ultraviolet wavelengths and the eclipse could be studied in some detail. An updated eclipse ephemeris was derived. The X-rays were shown to originate close to the white dwarf, the boundary layer, with significant absorption affecting its spectrum. There was no absorption in SDSS J103533.02+055158.3, despite being observed at the same inclination indicating different shapes of the disk and the disk rim. The white-dwarf temperature was re-determined for both objects: the white dwarf in OV Boo was still hot (23,000 K) five months after a dwarf nova outburst, and the white dwarf in SDSS J103533.02+055158.3 hotter than assumed previously (Teff = 11,500 K). All three cataclysmic variables with degenerate donors studied so far in X-rays, including SDSS J121209.31+013627.7, were clearly discovered in X-rays and revealed mass accretion rates dot(M) >= 8 x 10^(-15) Msun/ yr. If their X-ray behavior is representative of the subpopulation of period bouncers, the all-sky X-ray surveys with eROSITA together with comprehensive follow-up will uncover new objects in sufficient number to address the remaining questions concerning late-stage cataclysmic variable evolution.

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