(cba:news) superhumping stars...

[Joe Patterson]

Dear CBAers,

Just a quick note about present programs.  V1193 Ori has been a total
winner, with very powerful (negative) superhumps raging throughout the
last 3 weeks (Jennie, Tonny, Greg Bolt, Bart Staels, David Boyd)... and
even more so in November, when Alex Liu's data showed the damn thing at
0.38 mag full amplitude!  That's a new record for an average amplitude
over a long time span (2 weeks).  Our data follow this signal quite well,
and I think we can fondly wave the star off into the western horizon.
A superb job by both the star and its attendant humans.  Superhump at
0.1589(2) d and orbit at 0.1658(d) - the latter courtesy of John
Thorstensen, Holly Sheets, Fred Ringwald, and the Dartmouth Orbit Police.

The other evening star we've been struggling with is SDSS 0407-06 = Eri.
This eclipsing star also shows powerful negative superhumps, first founf
by Ak et al. (2005).  But the star dove into a semi-low state about 12
days ago; it looked like CBA coverage would no longer be productive,
although Bob Rea's lightcurves suggested a very large amplitude signal.
Anyway, the cba-chatters may have noticed that Tom Krajci found the star
back at ~15.5 a few days ago, so I hope we can squeeze out another 10-12
days of coverage while evening moonlight isn't too bad.

I've also forwarded this (probably) important IAU Circular.  The He II
emission makes me think of a supersoft binary - like V Sge - and it may be
a good target for small southern scopes.  But watch for saturation at
V=8.8!  By the way, be sure and check the referenced website by Sebastian
Otero.  This is a very interesting star!

More on northern and post-midnight stars in a day or two...

joe


                                                  Electronic Telegram No. 370
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS at CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT at CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html


HD 109962
     F. Walter, Stony Brook University; H. E. Bond, Space Telescope
Science Institute; and A. Pasten, Cerro Tololo Interamerican
Observatory, report that a spectrum obtained with the SMARTS 1.5-m
telescope spectrograph of HD 109962 (= NSV 19448) on Jan. 16.2 UT
shows He II 468.6-nm emission (equivalent width -0.29 nm)
superposed on the star's F2 V spectrum.  As described by S. Otero
(http://ar.geocities.com/varsao/NSV_19448.htm), HD 109962 is an
eclipsing binary with a period of 0.89 days that additionally shows
outbursts of about 0.8 mag and duration about 40 days occurring about
once a year, according to ASAS-3 data, with the latest outburst
having begun in late December 2005.  The He II emission suggests a
transient source of ionizing radiation, perhaps a compact object in
an eccentric orbit accreting in the stellar wind.  Observations at
all wavelengths, including x-ray and ultraviolet, are strongly
encouraged.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2006 CBAT
2006 January 19                  (CBET 370)               Daniel W. E. Green