Var73 Dra: "Twin" system with NY Ser
According to A&A 391, 565 (2002) Antipin and Pavlenko, Var73 Dra is
a long-period (Psh=0.0954 d) SU UMa-type dwarf nova. The light curve of
the outbursts strongly resembles those of a long-period system NY Ser (vsnet-campaign-dn
2761). B. Skiff reported that the Cambridge APM catalogue shows this
star at outburst on the later of the two overlapping POSS-I plates (epoch
1953.61;mb=15.8,mr=15.5, epoch 1952.63;mb=19.4,mr=19.5)(vsnet-campaign-dn
2762).
In October 2002, the Kyoto observations (observers: M. Uemura and R. Ishioka)
detected a bright outburst of Var73 Dra. The object was rising on October
4, and likely attained its maximum around October 9-10. The maximum was
around 15.0 mag or possibly brighter. These data showed variations of 0.2-0.3
mag, which are likely superhumps (vsnet-campaign-dn
2888, 2889,
2898).
The superhumps were most prominent on Oct. 9. B. Martin's observation
suggested that the amplitude of the superhumps then decreased, together
with possible appearance of secondary superhumps. T. Kato reported that
a preliminary period analysis suggested a period near 0.095 d, but a longer
alias (P=0.105 d) was also promising (vsnet-campaign-dn
2899).
The data taken by L. Cook on October 15 showed low-amplitude superhumps
(vsnet-campaign-dn
2903). In the terminal stage of the superoutburst, the light curve
taken by D. Starkey showed the persistent superhumps. G. Masi reported
that it was Rc=16.5 with broad late-superhumps on October 18 (vsnet-campaign-dn
2908). T. Kato performed period analysis and reported a revised superhump
period of 0.1051(2) d. This period would make Var73 Dra a "twin" system
with NY Ser, an SU UMa-type dwarf nova in the period gap (Nogami et al.
(1998) 50, L1), although other aliases are still possible (vsnet-campaign-dn
2906, 2900,
2901,
2909).
From the Kyoto observation on December 6, Var73 Dra was confirmed to be undergoing
another outburst. The brightness was comparable to that of the October superoutburst
(vsnet-campaign-dn
3082). T. Vanmunster performed time-series photometry for 2.66 hours
on Dec 8/9, and reported that small scale variations were clearly present
(vsnet-campaign-dn
3093). D. Starkey's observations confirmed that the outburst was a genuine
superoutburst. This finding suggests that the minimum supercycle length
of Var73 Dra is around ~60 d (or possibly slightly shorter). This shortness
of the supercycle is comparable to those of ER UMa-type dwarf novae. In
conjunction with Antipin and Pavlenko (2002) A&A 391, 565, the supercycle
of this object may not be as stable as in ER UMa stars. Such a variation
of the supercycles was also recorded in the in-the-gap SU UMa-type dwarf
nova, NY Ser (Nogami et al. 1998, PASJ 50, L1). Var73 Dra may be the first
ER UMa-like dwarf nova in the period gap (vsnet-campaign-dn
3100, 3098).
T. Vanmunster performed a new time-series observation on December 10/11,
and detected well developed superhumps (vsnet-campaign-dn
3107). He found a superhump period value of 0.1069 +/- 0.002. During
his first 2 nights, no clear hints of superhumps were present, and the average
amplitude of the light modulations was about 0.10 mag (vsnet-campaign-dn
3108, 3109,
3117,
3133).
Link:
Light curve taken by T. Vanmunster:
http://www.cbabelgium.com
[vsnet-campaign-dn
3093]
Charts and preliminary sequence presented by M. Simonsen:
http://joevp.20m.com/charts/provisional/
[vsnet-campaign-dn
3090]