RZ Leo : WZ Sge-type superoutburst

(A rare superoutburst occurred in the end of 2000.) A light curve observed by G. Masi shows one "early superhump" maximum on December 22 (vsnet-campaign 624). From the observation on December 25 by the Kyoto team and S. Kiyota, T. Kato reported the superhumps with narrower peaks and with an amplitude of 0.35 mag (vsnet-campaign 623). From a steep fading seen in December 27 data by the Kyoto team and S. Kiyota, T. Kato suggested there seems to be a wavy pattern with a period of 2-3 d in the averaged light curve. This is likely caused by the beat phenomenon between the superhump period and the orbital period, a natural consequence of a high-inclination system (vsnet-campaign 633). A brightening which was seen in the Kyoto team data on December 28 is consistent with the presence of the beat phenomenon (vsnet-campaign 637). The analysis of all VSNET collaboration data since December 23.5 UT up to the Kyoto December 29 full run has yielded the best superhump period of 0.07863 d (vsnet-campaign 640). Six days of continued intensive coverage of RZ Leo by various CBA stations, has allowed to further secure the superhump period of this system, yielding a value of 0.07862 +- 0.00012 d. Compared with Porb = 0.07604 +- 0.00012 d, this gives a fractional period excess of 3.4 +- 0.2 %. T. Vanmunster commented this is something of a surprise, as most of the infrequently erupting SU UMa CVs have much smaller period excesses, signifying a light secondary (vsnet-campaign 645). T. Kato commented the constant superhump period is rather atypical for SU UMa-type dwarf novae (vsnet-campaign 649). The observations on January 5 (S. Kiyota and the Kyoto team) confirmed that RZ Leo entered the rapidly fading stage (vsnet-campaign 658). T. Kato noted that clear "usual" superhumps persisted (double-wave modulations were not apparent) until the very start of the rapid fading (vsnet-campaign 660).

Superhump light curve by the VSNET collaboration team

The fading rate became gradual with time (vsnet-campaign 669), and then, the fading almost stopped on January 11 (vsnet-campaign 671). On January 12, R. Ishioka, at Kyoto, found a re-brightening of the object (vsnet-campaign 672). T. Kato mentioned the interval between the fading from the main superoutburst and the rebrightening is only ~5 days, which is one of the shortest ever observed in SU UMa-type dwarf novae (vsnet-campaign 673). Although low-amplitude variations were present, superhumps during the rebrightening were less prominent than on January 4 (vsnet-campaign 674). The fading from the rebrightening started on January 13 (vsnet-campaign 680, 684). The Kyoto observation (observer Uemura) on January 14 confirms that the rapid fading of RZ Leo stopped. The brightness level above quiescence is rather reminiscent of the inter-rebrightening period of the WZ Sge-type star EG Cnc (vsnet-campaign 687). On January 15 and 16, modulations close to the orbital/superhump period have became more evident. Very preliminary period analysis favors the superhump period, which may suggest that the tidally distorted disk remained. The situation looks very similar to that of EG Cnc (vsnet-campaign 694, vsnet-campaign 697).

Other related articles: vsnet-campaign 626, 630, 634, 653, 657, 666, 681, vsnet-campaign-dn 354, 379, vsnet-campaign-data 57

Lightcurves presented by J. Pietz: http://home.t-online.de/home/Jochen.Pietz/rzleo1.gif http://home.t-online.de/home/Jochen.Pietz/rzleo2.gif

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