一个新的亚周期极小值CV的氢部分耗尽和螺旋盘结构的证据
A New Sub-Period-Minimum CV with Partial Hydrogen Depletion and Evidence of Spiral Disk Structure
摘要：
我们提出了CSS 120422：111127+571239（= SBS 1108 +574）的时间分辨光谱学和光度学，最近发现的SU UMa型矮新星，其55分钟的轨道周期远低于CV周期最小值~78分钟。与大多数其他已知的CV相比，它的光谱特征是He I发射的强度与巴尔末线相当，这意味着氢丰度小于长周期CV的0.1-但仍然比AM CVn星高至少10倍。总之，短的轨道周期和显著的氦氢比表明，“CSS 1204”的质量转移开始于施主恒星的主序星寿命结束时，这意味着该系统可能是Podsiadlowski，Han和Rappaport（2003）描述的AM CVn祖先。此外，Halpha线的多普勒断层图像揭示了两个不同的增强发射区域。虽然一个是流盘碰撞的结果，另一个可能是由于螺旋盘结构时，在外盘的材料实现了2：1的轨道共振相对于施主产生的。
英文摘要：
We present time-resolved spectroscopy and photometry of CSS 120422:111127+571239 (= SBS1108+574), a recently discovered SU UMa-type dwarf nova whose 55-minute orbital period is well below the CV period minimum of ~78 minutes. In contrast with most other known CVs, its spectrum features He I emission of comparable strength to the Balmer lines, implying a hydrogen abundance less than 0.1 of long period CVs---but still at least 10 times higher than than in AM CVn stars. Together, the short orbital period and remarkable helium-to-hydrogen ratio suggest that mass transfer in "CSS 1204" began near the end of the donor star's main-sequence lifetime, meaning that the system is probably an AM CVn progenitor as described by Podsiadlowski, Han, and Rappaport (2003). Moreover, a Doppler tomogram of the Halpha line reveals two distinct regions of enhanced emission. While one is the result of the stream-disk impact, the other is probably attributable to spiral disk structure generated when material in the outer disk achieves a 2:1 orbital resonance with respect to the donor.
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