(cba:news) QR And, V378 Peg, VZ Scl
jop at astro.columbia.edu
Wed Nov 6 08:13:30 EST 2013
A few stars to update their status on our menu.
QR Andromedae. Job done. We have enough eclipse timings to measure the
rate of orbital-period change, which is very fast (timescale of 2x10**6
years). Just like T Pyx and V Sge, and possibly a *universal* signature
of supersoft binaries. We'll be trying this with a few others over the
next year, and test the hypothesis.
V378 Peg. I think we have enough. The star still exhibits the same
(exact) period seen by Ringwald and Kozhevnikov. Unfortunately we don't
have really decisive evidence of what Porb is... and almost certainly
that will require spectroscopy. (Ringwald published a spectroscopic P,
but the baseline was only 1 day, just not enough to clarify the matter.
We don't need more photometry now. The path forward now is probably
to guilt some spectroscopist to invest a few nights in studying the
VZ Scl. Wow. Josch Hambsch and Bob Rea invested some serious time in
this one, and the 3-week record revealed an obvious 3.3 hour negative
superhump. Wow - another high-Mdot "SW Sexer" coughs up its photometric
secrets (which it has been hiding for 40 years). It's now desirable to
make an intense effort for ~2 more weeks, to sharpen up the period, look
for harmonics, and the very-low-frequency (~4 d) signal usually
accompanying negative superhumps. It would be really good to get
coverage from some of the missing longitudes: Australia, Africa, and
(southern) Europe. With the deep eclipses exhibited by VZ Scl, it might
also be possible to trace the changing *shape* of the disk as a function
of "precession phase". We've never quite succeeded in this, but it
seems like it should be possible, for sufficiently big superhumps.
I hope to give similar status reports on other targets in a few days.
Berto has been observing ES Cet and a new dwarf nova, CSS
J024354.0-160314. The first is worth observing throughout the observing
season; the second, for at least a week. For those of you who don't
know the CRTS website, you'll be delighted to discover it. Among other
goodies, it supplies a finder chart and historical light curve.
Beautifully designed, and the source of all the CSS stars that are
starting to become an important part of the CV world.
Can someone clarify MASTER OT2348+25, the candidate helium star? How
bright is it now? If it's still doable, it's definitely the priority
target in the evening sky.
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