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arXiv 2011.04257astro-ph.SR
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室女座矮新星TW超爆发周围平静盘的演化

Evolution of the Quiescent Disk surrounding a Superoutburst of the Dwarf Nova TW Virginis

Zhibin Dai, Paula Szkody, Peter M. Garnavich

摘要:

利用光变曲线模型研究了矮新星TW Vir在静止时的Kepler K2短Cadence光变曲线。光变曲线分为24段,每段数据长度为$\sim\,$ 0.93 μ m,其中超爆发前4段,超爆发后20段。由于形态上的差异,静态轨道调制分为三种类型。使用固定的盘半径和两个分量恒星参数,所有来自截面的24个合成盘模型都显示出一致的配置,包括一个盘和两个热点:一个在盘边缘的垂直侧,另一个在盘的表面。在SO之前,盘和环形表面热点突然增强,触发前兆,然后SO。在SO之后和第一次正常爆发之前的静止期结束时,边缘热点变得更热,而表面热点切换到一个覆盖近一半磁盘表面的"冷却点”。在静止期间,表面热点总是位于盘的外部,具有恒定的径向宽度。盘的径向温度分布平坦,接近爆发时显得更平坦。与许多轨道周期为3- 5小时的U_(10)Gem型DN一样,传质速率明显低于CV演化的标准/修正模型的预测。

英文摘要:

Portions of the Kepler K2 Short Cadence light curve of the dwarf nova (DN) TW Vir at quiescence are investigated using light curve modeling. The light curve was separated into 24 sections, each with a data length of $\sim\,$0.93\,d, comprising 4 sections before and 20 after a superoutburst (SO). Due to the morphological differences, the quiescent orbital modulation is classified into three types. Using a fixed disk radius and the two component stellar parameters, all 24 synthetic disk models from the sections show a consistent configuration, consisting of a disk and two hotspots: one at the vertical side of the edge of the disk and the other one on the surface of the disk. Before the SO, the disk and a ringlike surface-hotspot are suddenly enhanced, triggering a precursor and then SO. At the end of the quiescent period following the SO and before the first normal outburst, the edge-hotspot becomes hotter, while the surface-hotspot switches into a ``coolspot" with a coverage of nearly one-half of the disk surface. During quiescence, the surface-hotspot is always located at the outer part of the disk with a constant radial width. A flat radial temperature distribution of the disk is found and appears flatter when approaching the outburst. Like many U\,Gem-type DN with orbital periods of 3-5\,hr, the mass transfer rate is significantly lower than the predictions of the standard/revised models of CV evolution.

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