Cool White Dwarfs in Cataclysmic Variables: Hubble Space Telescope Results on EG Cancri and HV Virginis
Cool White Dwarfs in Cataclysmic Variables: Hubble Space Telescope Results on EG Cancri and HV Virginis
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灾难变星中的冷白矮星：哈勃太空望远镜对 EG Cancri 和 HV Virginis 的结果
DOI：
10.1086/341116
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
S. Howell
中科院分区：
文献类型：
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作者：
P. Szkody;B. Gänsicke;E. Sion;S. Howell
我们的哈勃太空望远镜（HST）的低质量转移率激变变量EG Cnc和HV Vir在4年和8年过去的最后一次超爆发的紫外光谱表明，这些系统中的白色矮星是最冷的盘吸积近双星中观测到的。EG Cnc的紫外光通量与距离为350-475 pc的11，700 - 13，000 K白色矮星一致，而HV Vir的紫外光通量与距离为400-550 pc的12，500 - 14，000 K白色矮星一致，两颗恒星的log g = 8.0 ± 0.5。在每一种情况下，金属丰度都接近0.3个太阳，而旋转速率大大低于分裂。如果这些系统形成于周期间隙之上，并在几个Gyr的演化时间内演化到它们的短周期，那么它们的白色矮星比年龄相当的场白色矮星更热，比轨道周期相似的包含磁性白色矮星的密近双星系统更热。如果这些系统确实已经通过了演化过程中的最小周期，这意味着它们被来自其亲密同伴的质量转移的长期效应显著加热。
Our Hubble Space Telescope (HST) ultraviolet spectra of the low mass transfer rate cataclysmic variables EG Cnc and HV Vir at 4 yr and 8 yr past their last superoutburst have shown that the white dwarfs in these systems are among the coolest yet observed in disk-accreting close binaries. The UV-optical fluxes of EG Cnc are consistent with a 11,700-13,000 K white dwarf at a distance of 350-475 pc, while those of HV Vir fit with a 12,500-14,000 K white dwarf at 400-550 pc, with log g = 8.0 ± 0.5 for both stars. In each case, the metal abundance is near 0.3 solar, while the rotation rates are considerably less than breakup. If these systems formed above the period gap and evolved to their short periods in an evolution time of several Gyr, then their white dwarfs are hotter than field white dwarfs of comparable age and hotter than those in close binary systems of similar orbital period that contain magnetic white dwarfs. If these systems have indeed passed the period minimum in their evolution, the implication is that they are significantly heated by the long-term effects of mass transfer from their close companions.