Analysis of Three SU UMa-Type Dwarf Novae in the Kepler Field

Abstract

We studied Kepler light curves of three SU UMa-type dwarf novae: a background dwarf nova of KIC 4378554, V585 Lyr, and V516 Lyr. Both the background dwarf nova and V516 Lyr showed a combination of a precursor and a main superoutburst, during which superhumps always developed in the fading branch of the precursor. This finding supports that the thermal-tidal instability theory explains the origin of superoutburst. A superoutburst of V585 Lyr recorded by Kepler did not show a precursor outburst, and the superhumps developed only after the maximum light: namely, the first-ever example in the Kepler data. Such a superoutburst is understood based on the thermaltidal instability model to be a “case B” superoutburst, discussed by Osaki and Meyer (2003, A&A, 401, 325). From the observation of V585 Lyr, Kepler first clearly revealed the positive period derivative commonly seen in the “stage B” superhumps of dwarf novae with a short orbital period. In all three objects, there was no strong signature of a transition to the dominating stream impact-type component of superhumps. This finding suggests that there is no strong indication of an enhanced mass-transfer following the superoutburst. In V585 Lyr, there were “mini-rebrightenings” with an amplitude of 0.2–0.4 mag and its period of 0.4–0.6d during the period between the superoutburst and the rebrightening. We have determined that the orbital period of V516 Lyr is 0.083999(8)d. In V516 Lyr, some of outbursts were double outbursts with varying degrees. The preceding outburst in the double was of the inside-out nature, while the following one was of the outside-in nature. One of the superoutbursts in V516 Lyr was preceded by a double precursor. The preceding precursor failed to trigger a superoutburst, and the following precursor triggered a superoutburst by developing positive superhumps. We have also developed new methods of reconstructing the light curve of superhumps, and of measuring the times of maxima from poorly sampled Kepler LC data.

Survey of period variations of superhumps in SU UMa-type dwarf novae. VIII. The eighth year (2015–2016)

“…Tappert et al (2003) reported a line-profile analysis. Further superoutbursts were observed and reported in Kato et al (2009) (the 2006, 2008 superoutbursts), Kato et al (2010) (the 2010 superoutburst), Kato et al (2013a) outburst) and Kato et al (2014b) (the 2012 superoutburst).…”

“…The interpretation in Wood et al (2011) would suggest a high mass-transfer rate, and indeed "traditional" late superhumps with an ∼0.5 phase jump are seen only in systems with frequent outbursts (e.g. Kato et al 2013a). V1040 Cen, however, lacks frequent normal outbursts which are expected for a high mass-transfer rate.…”

“…This 2006 superoutburst was well studied by Imada et al (2008). The 2008 and 2011 superoutbursts were also observed and analyzed in ) and Kato et al (2013a), respectively. There was also a normal outburst on 2013 October 1 at V =15.0 (ASAS- SN and R. Stubbings;vsnet-obs 76596, vsnet-outburst 16054).…”

“…The second superoutburst in 2010 (hereafter 2010b) was reported in Kato et al (2012). Another superoutburst in 2012 was reported in Kato et al (2013a). riod was used to draw the figure compared to the earlier ones.…”

“…This paper is one of series of papers Kato et al (2009), Kato et al (2010), Kato et al (2012), Kato et al (2013a), Kato et al (2014b), Kato et al (2014a) and Kato et al (2015a) dealing with superhumps in SU UMa-type dwarf novae (DNe). SU UMatype dwarf novae are a class of cataclysmic variables (CVs) which are close binary systems transferring matter from a lowmass dwarf secondary to a white dwarf, forming an accretion disk.…”