(Outburst CCD image by Bernard Heathcote)
(Outburst CCD image by Peter Nelson)
V2051 Oph likely superoutburst
The recent outburst of the eclipsing SU UMa-type dwarf nova (cf. Kiyota and Kato 1998, IBVS No. 4644) V2051 Oph seems to have developed into a full superoutburst. Time-resolved CCD observations covering several orbital cycles are very strongly encouraged!
YYYYMMDD(UT) mag observer 20030409.650 <150 (Rod Stubbings) 20030413.756 145 (Rod Stubbings) 20030418.619 130 (Rod Stubbings)The eclipsing SU UMa-type dwarf novae can provide crucial information about the location and structure of the superhump light source, through contemporaneous superhump and eclipse observations. Please use short integration times (preferably around 10s) to record eclipse profiles in detail!
Excellent examples of eclipsing SU UMa-type dwarf novae can be found at the following URLs:
http://www.kusastro.kyoto-u.ac.jp/vsnet/DNe/tmzv85.html (IY UMa) http://www.kusastro.kyoto-u.ac.jp/vsnet/DNe/dvuma9912.html and links therein.See vsnet-alert 7707 for eclipse predictions.
(vsnet-campaign-v2051oph 28)
V2051 Oph likely superoutburst: observation by Bernard Heathcote
Dear Colleagues,
Bernard Heathcote communicated a preliminary report on the successful observation on V2051 Oph last night. The preliminary light curve shows clear presence of eclipses with depths of 1.0 mag. There is already a hint of low-amplitude superhumps outside the eclipses. Furthermore, there is evidence of "post-eclipse dips", which are sometimes observed in superoutbursts of high-inclination SU UMa-type dwarf novae. The nature of such dips has not been well clarified, and we encourage further full-orbit (several orbits) coverage, together with high time-resolution eclipse observations.
Regards, Taichi Kato VSNET Collaboration team
(vsnet-campaign-v2051oph 31)
Dear Colleagues,
We have received new exciting data from Roland Santallo (Apr. 20). The superhumps have become even clearer, and the depths of eclipses became smaller (0.5-0.7 mag) with rather complex detailed features. The profiles of eclipses and superposed superhumps were highly variable from time to time, as we experienced in the 2001 superoutburst of WZ Sge! V2051 Oph is apparently displaying another example of complex behavior in a short-period, high-inclination SU UMa-type dwarf nova in developing superoutburst! Please continue observing as long as possible, and we can expect even better conditions when the moon goes away.
Regards, Taichi Kato VSNET Collaboration team
(vsnet-campaign-v2051oph 32)
Dear Colleagues,
We have received new exciting data from Peter Nelson (Apr. 20) and Bernard Heathcote (Apr. 19). Combined with the earlier received observations, it is now established that "some of the eclipses show remarkable double minima profiles". The best example is presented on the VSNET website:
Such a kind of complex eclipse profile is rarely seen in outbursting eclipsing dwarf nova. The double minima indicate that there are two distinct sources on the accretion disk -- implying that we can now resolve the superhump light source! The overall change in the eclipse profile is even more reminiscent of WZ Sge 2001, whose complex evolution of the superhumps is still fresh in our memory!
In order to completely follow the beat-phase evolution of superhumps and eclipses, please make nightly observation as long as possible! V2051 Oph is sufficiently bright even at minimum, and we can expect high-quality post-superoutburst observations, too!
Regards, Taichi Kato VSNET Collaboration team
(vsnet-campaign-v2051oph 33)
Dear Colleagues,
We have received new observations (Apr. 21) from Peter Nelson, and Yasuo Sano. The object has been also intensively observed by the Kyoto team.
On April 21, the "double" profile of eclipses has disappeared, and the depth again increased to 1.0 mag. If this feature is related to the beat cycle, we can expect it to occur again, around tonight or tomorrow. The eclipse, however, is highly asymmetric, with a slower egress than ingress, indicating the presence of a bright spot (superhump light source) on the disk. The superhumps became less prominent, but are well trackable. The overall appearance of eclipses and modulating superhumps is very reminiscent of WZ Sge 2001 during the plateau stage. Further continued observations are strongly encouraged to solve the mystery of short-period eclipsing SU UMa stars!
Regards, Taichi Kato VSNET Collaboration team
(vsnet-campaign-v2051oph 34)
Dear Colleagues,
We have received new observations (Apr. 21-22) from Berto Monard. The data covered the most recent part of the current superoutburst. We have also received successful observation from Tanabe-san and Okayama U. Sci. team.
The most recent data show deep (1.2 mag) and sharp eclipses. The superhumps are clearly visible between the eclipses. The profile of the superhumps noticeably varied from cycle to cycle. On some occasions, there was a likely "dip" following superhump maxima. This was not, however, a very persistent feature. This phenomenon may be somehow related to "orbital dips seen in superoutburst" in some high-inclination SU UMa-type stars.
Regards, Taichi Kato VSNET Collaboration team
(vsnet-campaign-v2051oph 35)
Dear Collageus,
We have receive a huge amount of V2051 Oph observations from Kiyota-san, Nakajima-san, Chris Stockdale (two nights), Roland Santallo, Bernard Heathcote, and usual Kyoto and OUS teams. All the data show distinct eclipses and superhumps. We have put on the VSNET website orbital-phase averaged representative light curves of different segments of data between April 21 and 22.
The progressive phase variation of the superhumps is clearly seen. On April 21, the eclipses were slightly broad, while they become sharper on April 22. On April 22, there were prominent quasi-period variations (time-scales about 10 min) outside the eclipses, which comrpise a part of complex modulations on the phase-averaged light curve mentioned above. The eclipse profile on the same night also showed comparably complex structure to short time-scales. These QPO-like variation and structured eclipse feature may be associated.
As we can expect complex modulations, as seen on April 19, occurring just now, we encourage further dense time-series observation until the end of the current spectacular superoutburst!
Regards, Taichi Kato VSNET Collaboration team
(vsnet-campaign-v2051oph 36)
Dear Colleagues,
Based on the observations up to now, we yielded a superhump period of 0.06414 d. This period is slgihtly shorter than the previously adopted value. The fractional superhump excess with the new period is 2.7%. There is not striking evidence of period increase/decrease, but the conclusion should await a further analysis with full treatments of the eclipses.
Regards, Taichi Kato VSNET Collaboration team
(vsnet-campaign-v2051oph 39)
Dear Colleagues,
Chris Stockdale has kindly sent another set of high-quality observations on April 25 (we have also received a successful note from Peter Nelson). The object has faded at a rate consistent with that of a superoutburst plateau. The light curve displays well-structured superhumps (with multiple peaks) and structured eclipses. Further analysis of the data is in progress. V2051 Oph is still active, and we encourage further long, continuous observations!
Regards, Taichi Kato
(Bernard Heathcote, April 29)
(Chris Stockdale, April 30)
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