Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. II The Second Year (2009–2010)

Abstract

Continued from Kato et al. (2009, PASJ, 61, S395), we collected the times of superhump maxima for 68 SU UMa-type dwarf novae, mainly observed during the 2009–2010 season. The newly obtained data confirmed the basic findings reported in Kato et al. (ibid.): the presence of stages A–C and the predominance of positive period derivatives during stage B in systems with superhump periods shorter than 0.07 d. There was a systematic difference in the period derivatives for the systems with superhump periods longer than 0.075 d between this study and Kato et al. (ibid.). We suggest that this difference was possibly caused by a relative lack of frequently outbursting SU UMa-type dwarf novae in this period regime in the present study. We recorded a strong beat phenomenon during the 2009 superoutburst of IY UMa. A close correlation between the beat period and the superhump period suggests that the changing angular velocity of the apsidal motion of the elliptical disk is responsible for the variation of the superhump periods. We also described three new WZ Sge-type objects with established early superhumps and one with likely early superhumps. We suggest that two systems, VX For and EL UMa, are WZ Sge-type dwarf novae with multiple rebrightenings. The $O-C$ variation in OT J213806.6$+$261957 suggests that the frequent absence of rebrightenings in very short-$P_{\rm orb}$ objects can be the result of a sustained superoutburst plateau at the epoch when usual SU UMa-type dwarf novae return to quiescence, preceding a rebrightening. We also present a formulation for a variety of Bayesian extensions to traditional period analyses.

The evolutionary status of Cataclysmic Variables: eclipse modelling of 15 systems

“…Savoury et al 2011), new potential calibration systems have emerged, in addition to revised q values for existing calibration systems. Revised superhump periods have also been measured, courtesy of the SU UMa-type DNe survey of Kato et al (2009Kato et al ( , 2010Kato et al ( , 2012Kato et al ( , 2013Kato et al ( , 2014aKato et al ( ,b, 2015Kato et al ( , 2016Kato et al ( , 2017. With all of these new measurements becoming available since the work of Knigge (2006), it is appropriate to update the calibration of the (q) relation.…”

“…Given our updating of the superhump-mass ratio relations above, we revisit the analysis of donor star properties in Knigge (2006) and Knigge et al (2011). Firstly, P sh values for all SU UMa-type DNe in the Patterson et al (2005) sample (70 systems) were replaced by P B sh measurements from the SU UMa-type DNe survey of Kato et al (2009Kato et al ( , 2010Kato et al ( , 2012Kato et al ( , 2013Kato et al ( , 2014aKato et al ( ,b, 2015Kato et al ( , 2016Kato et al ( , 2017. For a number of systems, P orb was also updated, either from measurements made by Tables 2 and B1 Patterson et al (2005).…”

Spectroscopic Orbital Periods for 29 Cataclysmic Variables From the Sloan Digital Sky Survey

“…This is not surprising, since spectroscopy of fainter targets can be very difficult. It is fortunate, then, that many of the shortest-period CVs undergo superoutbusts and show superhumps, which can be used to derive approximate periods that are good enough for many purposes (see, e.g.. Kato et al 2009Kato et al , 2010.…”

“…When Szkody et al (2006) performed follow-up photometry on this object, they found it in outburst and discovered a 1.58 hr superhump modulation, implying an orbital period near 91 minutes. Kato et al (2010) report P sh = 93.54(4) minutes early in the outburst, increasing to 93.91(4) minutes later. Our spectroscopic orbital period is 90.86(13) minutes, so that…”

IW And-type state in IM Eridani

“…We used the phase dispersion minimization (PDM, Stellingwerf 1978) method to identify periods in the data. The error of the PDM analysis was estimated by the methods of Fernie (1989) and Kato et al (2010). Although we also applied the least absolute shrinkage and selection operator (Lasso) method (Tibshirani 1996;Kato and Uemura 2012) particularly using the two-dimensional version (Kato and Maehara 2013), we do show the result since we could not find particular advantage over the PDM method.…”