V485 Cen is in outburst.
V485 Cen 11 May <14.0 Time(UT) Mag.(Vis) 15 May 9:16 13.9Rod Stubbings
V485 Cen is known to be a unique dwarf nova having an orbital period of 59 min (!!), which is well below the "minimum period" of hydrogen-rich cataclysmic variables. For a reference, see Augusteijn et al. 1996, AsAp 311, 889. High-speed photometry is most urgently and strongly recommended.
(vsnet-alert 912, vsnet-obs 5798)
Paul Warhurst, University of Auckland, has reported a time series of differential photometry of the erupting dwarf nova V485 Cen, which clearly shows a wave at a period of 60+-3 min, close to the 59-minute orbital period discovered by Augusteijn et al. (1994). The full amplitude is about 0.18 mag.
Additional timings of this wave over the next 5-10 days, especially over a range of terrestrial longitudes, are critical to specify the nature of the wave in this mysterious star -- unique in the CV zoo. We would love to hear from observers who are able to obtain data. We have been using comparison stars 3 arcmin WNW and 1 arcmin W from the variable (chart in Downes & Shara, Feb 1993 PASP).
Center for Backyard Astrophysics (NY)
Preliminary analysis of the data (3-hr started at 1997.05.17,024 UT, 1-hr started at 1997.05.19,260 UT, 5-hr started at 1997.05.19,969 UT, and 6-hr started at 1997.05.20,964 UT) collected with the 1.3-m Warsaw telescope at Las Campanas Observatory as a subproject of the OGLE-2 project indicates that this star belongs to the SU UMa group of cataclysmic variables. The well-developed typical superhumps with amplitude 0.25 mag on the first night and 0.15 mag on the last night have period 60.6 min. Taking into account value of 59 min. for the orbital period given by Augusteijn et al (A&A, 311, 889) the period excess is 2.7%.
Congratulations to Rod Stubbings on announcing us such important outburst (cf. vsnet-alert 908), and to Paul Warhurst (vsnet-alert 912) and Arkadiusz Olech (vsnet 1034) for successfully detecting superhumps!
Exciting enough is the quoted value of fractional superhump excess (2.7%, Olech), which is quite larger than those of WZ Sge-type dwarf novae, similar short-orbital systems. Would it mean V485 Cen is not along the shorter-period extension of usual SU UMa-type dwarf novae, i.e. the secondary is more massive and denser?
Dip the light curve fo V485 Cen?
Observations of V485 Cen from May 16/17 to May 23/24 made with 1.3-m Warsaw telescope at Las Campanas Observatory show linear decrease of brightness of the star with rate of 0.1 mag/day. Data collected on the last night (May 24/25) showed rapid change of the rate of decline. In comparison with the night of May 23/24 the star faded over 0.5 mag. Is this the a begnining of a dip observed during superoutburst of some WZ Sge stars, or rapid end of the superoutburst?
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