Superoutburst of WX Cet

(vsnet-alert 472)

From: "Pam Kilmartin & Alan Gilmore, Mt John." (

Albert F. Jones, Nelson, New Zealand reports that the dwarf nova WX Ceti is bright:

           U.T.         mv
    1996 July 17.646   12.0   Thin cloud
              17.656   11.8
              17.684   11.6
              17.731   11.6

(vsnet-alert 471, Berto Monard)

Hi observers,

the UGWZ type dwarf nova (and TOAD) WX CET is in outburst as seen through the apogee 40x120 in Pretoria:

          UT      Magn
July 18.087   12.0
July 18.129   12.0 

Unfortunately I have no earlier observations due to bad weather.

If the outburst turns out to be tremendous the star will become brighter than 10th magnitude.
Please monitor WX CET. At declination -18 it is in reach for most Northern observers. Give it a go!

Best regards,

Berto Monard / AAVSO observer MLF

VSNET chart

Outburst CCD image (Ouda Station)

link to AAVSO News Flash No. 39

compliation of VSNET observations

Comment by T. Kato

(vsnet-alert 473)

Maximal magnitudes of superoutbursts of WX Cet tend to have a large scatter (~3 mag) as compared with other 'usual' SU UMa-type dwarf novae (e.g. T. Kato, IBVS No. 4256). From this point, the present magnitude already suggests a superoutburst. Since strong aliasing of previous superhump observations has not yet completely solved, there are much to be done regarding superhump photometry. 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 fainding tail of the 1978 superoutburst of WZ Sge. Observers are strongly urged to closely monitor this still enigmatic dwarf nova.

Taichi Kato

Detection of superhumps (Patterson)

(vsnet-obs 3160)


Photoelectric photometry on the CTIO 1-m by Jonathan Kemp and Susan Kassin showed 0.25 mag superhumps in WX Ceti on the night of July 17/18. Thus the present outburst is very likely to be a supermax, as suspected by Kato (yesterday's vsnet). Congratulations K(emp)K(assin)K(ato), and of course also Berto Monard and Albert Jones who rang the alarm.

A July supermax isn't perfect (we'd really like October), but it's still the best seasonal timing WX Cet has ever delivered. O'Donoghue et al. (1991; MNRAS 250, 363) struggled valiantly to find the superhump period from single-site observations in early June 1989. Their best- fit periods were in the range 70-80 min, an awfully interesting range! But these were based on observations of only ~2 hr/night (because of the unfavorable location of Cetus in June), far too brief to identify the period securely. Thus the superhump period remains unknown.

Now we can fix that. But it probably requires a multi-longitude star, still uncomfortably short. We would love to hear from other observers who are able to get superhump timings. At magnitude 11.7 and with a full amplitude of 0.25 mag, the project may even be feasible for very experienced visual observers.

WX Cet is sometimes classified among the WZ Sge stars. These stars are probably not distinct in any deep way from the SU UMa class, being essentially the most infrequent erupters in that class. But the evidence on this point is still slim; these stars erupt so seldom that we ought to leap into action when the opportunity for study finally arrives.

So set the VCR to tape the Olympics, and get thee to a telescope.

Joe Patterson
Dept. of Astronomy, Columbia Univ.

Superhumps update


(vsnet-alert 502)

Dear Colleagues,

We Ouda Team have caught a re-brightening of WX Cet as following! The behavior of this variable from now deserves close monitoring in order to clarify whether this re- brightening is leading to the second superoutburst as observed in AL Com last year or will end up as a normal outburst.

      Mid-UT      V mag
CETWX 960730.758  13.82 Oud
CETWX 960731.784  14.85 Oud
CETWX 960802.774  15.45 Oud
CETWX 960805.768  16.50 Oud
CETWX 960807.807  15.45 Oud
CETWX 960808.793  14.15 Oud

Seq. VSNET chart
60cm refl.+CCD+V filter at Ouda Station
Best Regards,
Daisaku Nogami and Hajime Baba

Tale of the Whale

(vsnet 722)

Summary of WX CET observations, July 1996 superoutburst.

UT date       Observ.

18.38     11.87   CTIO
19.35     11.95   CTIO
20.38     12.12   CTIO
21.33     12.32   CTIO
22.37     12.48   CTIO
23.37     12.65   CTIO
27.73     12.98   Ouda
29.72     13.25   Ouda
30.78     13.88   Ouda
31.78     14.85   Ouda
33.77     15.45   Ouda
36.77     16.50   Ouda
37.35     16.70   CTIO
38.81     15.45   Ouda
39.29     13.85   CTIO
39.79     14.15   Ouda
40.27     15.19   CTIO
40.42     15.57   CTIO

A common superhump of 85.5 min was seen during the bright phase of the eruption.

A dwarf nova oscillation was seen at 17.38 seconds on July 23.

A "second peak" was seen to occur at about July 39.2 = August 8.2 (previously noted by Nogami & Baba, vsnet-alert 502). The light then declined rapidly at 1.5 mag/d, a rate characteristic of the "normal maxima" of short-Porb dwarf novae.

On all three nights of the CTIO August coverage, a quasi-periodic oscillation with P=9-10 min was observed.

This is a critical moment in the life of WX Cet. Is this the final decline, or will it leap back up again? WZ Sge and AL Com showed a little echo like this, followed by something like a "second superoutburst" (considerably fainter though). This second outburst was studied only quite poorly, and not at all for other SU UMas (assuming they have such events, which seems plausible though just a guess). So there could be an excellent chance here to help remove the mystery surrounding this particular phase of dwarf-nova eruptions. Take a break from meteors and Martians, and put your faith in the Whale.

Joe Patterson and Jonathan Kemp
Columbia Univ. and CBA

Return to HomePage