V803 Cen: likely start of a new supercycle
Very bright outburst. See e.g. Kato et al. (2000) IBVS 4915.
YYYYMMDD(UT) mag observer 20030525.406 <150 (Rod Stubbings) 20030526.425 <150 (Rod Stubbings) 20030527.394 <148 (Rod Stubbings) 20030528.519 <145 (P. Williams) 20030528.574 <148 (Rod Stubbings) 20030530.426 <148 (Rod Stubbings) 20030531.719 <146 (Berto Monard) 20030602.401 <146 (Rod Stubbings) 20030604.476 126 (Rod Stubbings) 20030604.485 126 (Rod Stubbings)
V803 Cen superhumps
Dear Colleagues,
We have received a nice data set from Neil D Butterworth. The light curve clearly indicate the presence of 0.06 mag superhumps. The period determined from this observation is 0.01860(8) d, which agrees with the "nominal superhump period" of this system within errors. The profile is placed at:
Although the light curve may look slightly noisy, mainly because of the low amplitude of the variations, the presence of the superhump-type variation is secure.
Regards, Taichi Kato VSNET Collaboration team
Dear Colleagues,
We have received a very exciting data set from Neil Butterworth. The object stays bright at supermaximum, and showing flashing superhumps!
From the two night' baseline, we have been able to precisely determine the superhump period to be 0.018674(6) d = 1613 s.
Regards, Taichi Kato VSNET Collaboration team
V803 Cen started rapid fading!
Dear Colleagues,
We have received new, again very exciting, data from Greg Bolt and Neil Butterworth. On June 8, the object started fading *very* rapidly. The fading rate (of the initial part of the decline) was 4.2 mag/d !! During this fading, the superhump signal became stronger (in amplitude), and the profile became slightly doubly humped.
From what we have learned in the past observations of V803 Cen and CR Boo, this stage lasts for only a brief time, and the object will soon rebrighten to a certain magnitude (somewhere below the superoutburst maximum), and start oscillating. The present outburst will provide an excellent opprtunity to follow the evolution of the outburst and superhumps, and we encourage intensive coverage.
Regards, Taichi Kato VSNET Collaboration team
V803 Cen: further observations from Berto Monard
Dear Colleagues,
We have received further data (two nights) from Berto Monard. The early stage of the V803 Cen superoutburst has been exquisitely recorded! The superoutburst plateau phase lasted at least until the June 8.0 UT. The object entered the rapid fading stage probably at around June 8.5. The object faded by 1 mag within the next 10 hours! Althought the fading become slightly slower, the linear fading trend continued at least until June 9.0 UT. Superhumps were singly peaked during the early plateau phase, but secondary maxima appeared during the rapid fading stage (comprising our "familiar" profile in helium SU UMa-type star). This behavior resembles "late superhumps" in hydrogen-rich SU UMa-type stars, although there is a slight difference of relative amplitudes of main and secondary superhump maxima between V803 Cen and hydrogen-rich SU UMa stars. The present epoch corresponds to the earliest stage of a superoutburst, and the object is expected to rebrighten to a longer-lasting superoutburst plateau stage. Please keep observing!
Regards, Taichi Kato VSNET Collaboration team
V803 Cen: strong oscillations!
Dear Colleagues,
Berto Monard has reported a new exciting set of data! Following Tom Richard's observation, V803 Cen turned to a steep beightening stage. After reaching a sharp peak on June 10.87 UT, the object started fading again (at a slower rate). During this observation, superhumps were only transiently active. The overall variation bears some resemblance to post-superoutburst rebrightening in a hydrogen-rich dwarf novae (similar to the 13 rebrightenings in WZ Sge in 2001, http://www.kusastro.kyoto-u.ac.jp/vsnet/DNe/wzsge01.html, but there is a difference in the behavior of superhumps). In any case, the light curve looks extremely queer among all sorts of variable stars!
Regards, Taichi Kato VSNET Collaboration team
V803 Cen: brightened again!
Dear Colleagues,
We have received new data from Berto Monard and Greg Bolt. Following the fading reported by Monard on June 11, V803 Cen returned to its maximum (plateau) phase 1 day later, and subsequently showed a precipitous decline. On the next night, the object brightened again! The amplitudes of these oscillations were initially about 1 mag, and seem to be damping. Very dense observations are absolutely needed to record the full variation of this monster variable star! The superhump signal has been only weakly seen during this oscillation stage.
Regards, Taichi Kato VSNET Collaboration team
V803 Cen: oscillation continues
Dear Colleagues,
We have received new data from Greg Bolt. During the 6-hr observation, V803 Cen initially faded, but reached a minimum around June 14.65 UT. The amplitude of the continuing oscillation is slightly less than 1 mag.
The maxima of the oscillations have been linearly fading at a mean rate of 0.1 mag/d, which is on a smooth extension from the initial superoutburst plateau. The overall behavior (period and amplitude) of the current oscillation stage is _stikingly similar_ to the "post-dip" behavior of WZ Sge observed during its 2001 superoutburst. The overall bahevior since the start of the superoutburst resembles that of the later half of the WZ Sge superoutburst (pre-dip to oscillation stage). This analogy may suggest that the outburst of a helium dwarf nova can be understood as an extension of the WZ Sge-type outbursts (see also Osaki and Meyer 2003, A&A 401, 325 for the modern view of the WZ Sge-type outbursts).
Regards, Taichi Kato VSNET Collaboration team
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