(cba:news) VX For superhumps

[Joe Patterson]

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 at mweb.co.za>
To: cba-news at cbastro.org <cba-news at cbastro.org>
CC: Vsnet-Alert at Ooruri.Kusastro.Kyoto-U.Ac.Jp 
<vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp>

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