(cba:news) superhumping stars...
jop at astro.columbia.edu
Thu Jan 19 09:44:40 EST 2006
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...
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)
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
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
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