(cba:news) stars for april

Joe Patterson jop at astro.columbia.edu
Tue Apr 5 10:07:50 EDT 2005

Dear CBAers,

Plenty of activity in CBAland recently.  The coverage on N Pyx 05
(actually a dwarf nova, name not yet assigned) has been excellent, but the
star is now too faint for most of you - so I recommend you sweep it off
the stage.  The power spectra of the spliced shows not only the main
superhump signal (at 15.94 c/d) but also the little fine-structure peaks
separated by 0.28 c/d, which reveals the precession frequency.  When we
get coverage this good, we can usually measure nu-orb (in this case
15.94+0.28=16.22) even without waiting for observations at quiescence.
Kudos to the usual Southern hotshots on this one: Berto, Jennie, Bob Rea,
Tom Richards, Greg Bolt, Bill Allen, Alex Liu (though Alon Retter).

Boreal regions have had a nice show too, courtesy of RX0532+62, another
newly-popped-up dwarf nova.  This one's pretty strange. We caught the
"normal max" just prior to the supermax, and have now tracked it for 20
consecutive days.  Superhumps started to develop on the declining branch
of the normal max, which I think has never been seen before (though
excuses could be found for it). The superhumps came on like gangbusters
(American slang for "big and irresistible"), but have now - several mag
below max - become hard to spot amid the very large rapid flickering in
the star.  Very annoying, this flickering... if we could find some pattern
in it, it would be a fascinating thing to study - but so far I haven't
managed to find anything.  I'm inclined to suggest that we give up on this
star; but it has tossed some surprises at us, and maybe has one more.
If you're feeling lucky, keep it up!

But my general feeling is that it's time for a major house cleaning.
Delete YY Dra, N Pyx 05, and maybe RX0532+62.  In the south, I recommend
starting a campaign on CP Puppis - a famous old nova which we've never
attacked in a serious way.  Good target for the dark of the Moon.
Later in the night, V391 Hya (a little brighter at 14.3) is a good target
- we still haven't managed to find a period in this 14th mag novalike.
I'm inclined, for the reasons stated by Berto yesterday, to regard the new
star in Serpens as a likely nova, not dwarf nova - and hence not likely to
be a good target for photometry now.  I could be wrong in one or both of
these... but that's my current feeling. ("Not good" basically means
"unlikely to yield a periodic signal", by the way.)

In the north, I recommend BK Lyn as primary campaign target, but also
would love to see time series on RX0625+73 and BG CMi.\


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