CU Vel outburst: call for time-resolved photometry
As reported in [vsnet-outburst 4872], the SU UMa-type dwarf nova CU Vel is in outburst.
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CU Vel in outburst VELCU 021210.507 108 Stu.RASNZ VELCU 021210.521 108 Stu.RASNZ Regards, Rod Stubbings===
Surprizingly, no solid publication exists on the superhump observation of CU Vel. Although the present outburst may be yet premature to determine its nature, the long lack of outbursts preceding this outburst may suggest a superoutburst. Please make intensive time-series observations to obtain the (potentially first) full coverage of an outburst of this object.
The generally adopted superhump period is 0.07999 d. This period would be a good measure for the required minimal length (2-3 superhump periods) of the nightly runs.
Regards, Taichi Kato VSNET Collaboration team
CU Vel superoutburst: superhump detection by Greg Bolt!
Dear Colleagues,
Greg Bolt has sent us a time-series run of CU Vel taken on December 11. The light curve clearly shows superhumps, confirming that the present outburst is a superoutburst.
In addition to superhumps, there is strong evidence of super-QPOs with relatively large amplitudes. The light curve just looks like the first night observation of the superoutburst of EF Peg in 1991 (Kato (2002), PASJ 54, 87; VSNET preprint at http://vsnet.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/EF_Peg/).
The similarity of the pattern of super-QPOs and early-stage superhumps with that of EF Peg may suggest these features may be closely associated with long-period SU UMa-type dwarf novae with relatively rare superoutbursts.
Further observations throughout the current superoutburst are very strongly encouraged!
Regards, Taichi Kato VSNET Collaboration team(vsnet-alert 7593)
CU Vel: superoutburst update, superhump period
Dear Colleagues,
We have received further data from Greg Bolt. On December 14, the superhumps have fully grown with an amplitude of 0.25 mag. Prominent super-QPO-type signal on Dec. 11 looks like to have disappeared.
From the available observations, we have determined a preliminary superhump period of 0.07927(2) d, which is significantly shorter than the perviously adopted value. However, this period is only 1% larger than the adopted orbital period (0.0785 d). Such a small superhump period excess is very rare among long-period (long-Psh) systems, but is more common in WZ Sge-type stars. This possible small period excess may be a result of a small mass-ratio (q=0.12, Mennickent and Diaz (1996) A&A, 309, 147). Otherwise, it may be also possible that the superhump period may have not been stabilized yet.
Both the discrepancy from the past observation and the possiblly unusually low superhump period excess strongly encourage us to further observe the present CU Vel superoutburst in detail throughout the course of the superoutburst. We may even expect that some features similar to those of WZ Sge stars can appear. As long as the object is observable, please make as long observations possible (hopefully more than 3 hours per night)! The object is currently the top-priority southern target.
Regards, Taichi Kato VSNET Collaboration team(vsnet-campaign-dn 3136)
CU Vel: superhump period
Dear Colleagues,
We have received further data from Tom Richards. A preliminary analysis of the data has yielded a superhump period of 0.0809-0.0811 d, depending on the selection of the calculated bins. These periods are significantly longer than the previous value, and the generally adopted value. It may be possible that CU Vel is currently experiencing a phase of rapid period ecolution, or that the previously reported value had a large error. We need further intensive observations to clarify this situation.
At a period of Psh = 0.0811 d, a fractional superhump excess can be one of the largest among SU UMa stars.
Regards, Taichi Kato VSNET Collaboration team
CU Vel: superhump period update
Dear Colleagues,
We have received further revised observations, with which we can now derive the firm superhump period of 0.08085(3) d. The first night observation does not seem to be in line with this period, indicating that a dramatic evolution of the superhumps was witnessed. Further analysis is in progress.
Please continue these excellent works!
Regards, Taichi Kato VSNET Collaboration team
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