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
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!
Berto Monard / AAVSO observer MLF
Outburst CCD image (Ouda Station)
link to AAVSO News Flash No. 39
compliation of VSNET observations
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.
WX CETI, GETTING MAYBE A LITTLE LESS BASHFUL
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.
Dept. of Astronomy, Columbia Univ.
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 StationBest Regards,
Summary of WX CET observations, July 1996 superoutburst.
(July) 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
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