Superoutburst of WX Cet in 1998

(Overall Light Curve of the 1998 Superoutburst by the VSNET Collaboration)

Outburst!

WX Cet is in outburst, visual observations

 Star      Date      UT      Mag.
WX Cet    981108    11:11   <15.0
          981110    11:27    11.8

Rod Stubbings
Drouin, Vic.
Australia.

(vsnet-alert 2358)

WX Cet rare outburst

The SU UMa-type dwarf nova WX Cet is undergoing a rare outburst. The latest two outbursts were observed in 1996 July (superoutburst) and 1997 September (short outburst).

  YYMMDD(UT)   mag  observer
  981101.471  <138  (R. Stubbings)
  981102.527  <130  (R. Stubbings)
  981105.440  <131  (R. Stubbings)
  981106.454  <150  (R. Stubbings)
  981108.466  <150  (R. Stubbings)
  981110.477   118  (R. Stubbings)

Maximal magnitudes of superoutbursts of WX Cet tend to have a large scatter (about 3 mag) as compared with other 'usual' SU UMa-type dwarf novae (e.g. T. Kato, IBVS No. 4256; another example SW UMa). From this point, the present magnitude may already suggests a superoutburst. WX Cet showed another rather preculiar feature during the final fading stage of a superoutburst. In contrast to most SU UMa-type dwarf novae (including an extreme case of AL Com, the termination of the 1991 superoutburst was not accompanied by a rapid decline -- somewhat remniscent of the long fading tail of the 1978 superoutburst of WZ Sge. Observers are strongly urged to closely monitor this still enigmatic dwarf nova.

Regards,
Taichi Kato

(vsnet-alert 2363)

Visual magnitude estimates by P. Schmeer, Bischmisheim, Germany:

 
WX CETI  (UGSU)
Nov. 10.857 UT,  12.0 ; 10.906,  11.9
Sequence:   AAVSO
Instrument: 203-mm SCT

First night for several days with longer clear spells. No previous WX Cet observations this month due to clouds. The most recently observed supermaximum was independently detected by A. Jones, P. Schmeer, D. Overbeek, and B. Monard on the morning (local time) of 1996 July 18th (the same night TWA-800 crashed). So far no superoutburst of WX Cet has been visually observed in the evening sky.

 
Regards,
Patrick

P.S.: BC UMa is another SU UMa-type dwarf nova with bright (mag 11) and faint (mag 13) supermaxima.

Early Stage Superhumps

(vsnet-alert 2369)

WX Cet CCD observation (Ouda team) Nov. 11

We (K. Matsumoto and T. Kato) observed WX Cet using a 25-cm telescope and an unfiltered ST-7 CCD camera. The time-series observation on Nov. 11 has shown a gradual fade at a rate of 0.34 mag/day. Well-marked superhumps had not yet evolved. A period analysis favored a hint of modulation with a period near 0.06 day, having a full amplitude of 0.019 mag. The short time coverage, however, was not enough to discriminate the possibilities of Porb or Psh.

Regards,
Ouda team
K. Matsumoto and T. Kato

Clear Superhumps

(vsnet-alert 2373)

WX Cet clear superhumps (Ouda team)

We (K. Matsumoto, D. Nogami, T. Kato) observed WX Cet using a 25-cm rooftop telescope and an unfiltered ST-7 CCD on November 12 night. Preliminary reduction has revealed the clear apperance of superhumps (amplitude 0.18 mag), truly qualifying the present outburst as a genuine superoutburst. A rough period analysis gives 0.060 +/- 0.001 day for the superhump period. More detailed results will become available later today.

Regards,
K. Matsumoto,
D. Nogami,
T. Kato

(vsnet-alert 2376)

WX Cet: improved superhump period

From the whole dataset of our Nov. 12 run (vsnet-alert 2373), we have obtained the best estimate of the superhump period as 0.0599 +/- 0.0003 day. This rejects any one-day alias ambiguity in period determination during the 1996 superoutburst and earlier ones.

Regards,
K. Matsumoto,
D. Nogami
T. Kato,

(vsnet-alert 2378)

WX Cet superhumps update

Using the preliminary analysis of the Nov. 13 run, we have obtained the best superhump period of WX Cet on two-night basis as 0.05944 +/- 0.00005 day. Superhumps have grown slightly, with an amplitude of 0.20 mag. The obtained superhump period is significantly shorter than that obtained during the 1996 superoutburst. WX Cet had faded by ~0.2 mag compared to Nov. 12.

Regards,
T. Kato,
D. Nogami,
K. Matsumoto,
Ouda team

(O-C variation of superhumps. The superhump period is clearly increasing, in contrast to many other SU UMa-type dwarf novae).

(O-C variation of superhumps. The location of WX Cet among SU UMa-type dwarf novae is shown. The other systems showing a period increase are WZ Sge-type stars and related objects).

Rapid Fading Stage

(vsnet-alert 2404)

WX Cet: start of rapid fading?

We have just started this evening's CCD observations of the super- outbursting WX Cet. From the quick-look image, WX Cet seems to have been entering its rapid declining stage from the superoutburst. WX Cet showed a rather peculiar fading pattern during this stage in I-band, as extracted from my article in IBVS 4256:

> Another peculiar feature of WX Cet can be found during its terminal
> decline from a superoutburst.  In contrast to most SU UMa-type dwarf
> novae, the rate of decline slowed down far before reaching quiescence.
> [Averaged decline rates of 0.80 mag/day and 0.41 mag/day
> were obtained for the intervals of July 20 -- 22 and 22 -- 23,
> respectively. Note that WX Cet was at Ic=15.5 on July 23, which was
> $\sim$ 2.0 -- 2.5 mag brighter than quiescence.]  Similar phenomenon
> was also observed in CT Hya (Nogami et al. 1995).  Phenomenologically
> this feature seems to be related to a poorly understood long-fading tail
> observed in the terminal stages of superoutbursts of WZ Sge
> (Patterson et al. 1981), although its explanation should await further
> observational and theoretical works.

Observations are strongly urged during this important stage of the important superoutburst.

Regards,
Taichi Kato

(vsnet-alert 2405)

WX Cet nightly averaged magnitudes

  Unfiltered CCD time-series by the Ouda team:

    mid-UT    WX-C   S.D.  N  band
 ----------------------------------
  981111.526  1.713 0.033 172 C
  981112.514  1.743 0.074 375 C
  981113.577  1.895 0.101 341 C
  981114.536  1.995 0.108 484 C
  981115.505  2.155 0.109 435 C
  981117.597  2.348 0.109 442 C
  981118.535  2.504 0.048 815 C
  981119.559  2.634 0.052 656 C
  981120.487  2.682 0.059 400 C
  981122.582  2.778 0.061 492 C
  981123.555  2.876 0.114 404 C
  981124.626  3.073 0.125 244 C

  C = Tycho V=10.92 star

  observer: Ouda team (T. Kato, M. Katsura, D. Nogami)
  telescope: Ouda team rooftop station, 25-cm SCT + ST-7 unfiltered

(vsnet-alert 2419)

WX Cet: rebrightening or not?

Days have passed since the dramatical superoutburst and fading of WX Cet. In the 1996 superoutburst, WX Cet rose up about a week past the fading. The present time closely corresponds to the 1996 rebrightening phase. Please keep the close watch whether the rebrightening will repeat on the current occasion, and report your observations. Having been rarely caught in the rebrightening rise stage (even in that EG Cnc, observations during the rise to a rebrightening will be of utmost importance in revealing the underlying physics. WX Cet: rebrightening or not?