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(cba:news) VX For superhumps (Joe Patterson) [2009-09-16T10:37:19Z]



Rod's great discovery a few days ago was followed by Berto's first night of photometry last night... which showed obvious humps, quite likely to be superhumps (meaning with a period slightly longer than the precise Porb). I'm attaching Berto's announcement. So it's an SU UMa, case closed. That's pretty significant too; in the star's only historical outburst (1990) the star was first suspected to be a supernova, mostly because of its presence in Fornax, where galaxies are numerous and eruptive variables are rare. The spectrum showing zero-redshift features proved it was galactic, but my failure to find periodic humps with quite good data over 1 week was puzzling.

And it's still puzzling, unless Rod caught it well after the outburst started. If any of you have information or an educated opinion - or even an uneducated opinion - as to when the present outburst really began, I'd love to hear it.

I think it's very likely to be a full-bore, certifiable, card-carrying WZ Sge star. Every piece of evidence suggests that, except this latest (so far weak) indication that superhumps appeared practically at the start of outburst. (That's why estimating the true start is quite important.) Anyway, this should be a great, great target for time-series photometry as long as it stays bright - which I expect to be two weeks or more.

joe


-------- Original Message --------
Subject: [vsnet-alert 11476] VX For
Date: Wed, 16 Sep 2009 11:23:20 +0200
From: Berto Monard <bmonard@xxxxxxxxxx>
To: cba-news@xxxxxxxxxxx <cba-news@xxxxxxxxxxx>
CC: Vsnet-Alert@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx <vsnet-alert@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>

Timeseries photometry with unfiltered CCD of VX For at CBA Pretoria on the night 15-16 Sep 2009 show modulations with amplitude around 0.2 and period around 1.5h. The mean magnitude was 12.9CR.

Astrometry vs UCAC2 determines VX For at position 03 26 45.72 -34 26 24.6 (2000) This is exactly the same value as in the 2006 D&S catalogue.

For photometric comparison I have used a star at position 03 26 57.8049 -34 28 00.090 with a derived R magnitude 13.2 .

This star is an easy target for southern observers.

Regards,

Berto Monard / CBA Pretoria