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

• Published in: The Astronomical journal 2021-01, Vol.161 (1), p.34
• Main Authors: Dai 戴智, Zhibin 斌, Szkody, Paula, Garnavich, Peter M.
• Format: Article
• Language: English
• Subjects: Astronomical models; Astronomy; Dwarf novae; Evolution; Light curve; Mass transfer; Orbits; Stellar evolution; Switches; Temperature distribution
• ISSN: 0004-6256; 1538-3881
• DOI: 10.3847/1538-3881/abc8eb

In this paper, we investigate portions of the Kepler K2 Short Cadence light curve of the dwarf nova (DN) TW Vir at quiescence, using light-curve modeling. The light curve was separated into 24 sections, each with a data length of ∼0.93 days, comprising 4 sections before, and 20 after a superoutburst (SO). Due to 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 these 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 on the surface of the disk. Before the SO, the disk and a ringlike surface-hotspot are suddenly enhanced, triggering a precursor, and then the 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 half of the disk’s 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.