(cba:news) stars for nov-dec

[Joe Patterson]

Dear CBAers,

BW Scl has come down from its plateau, and is now at 14.6 - 2 mag 
brighter than quiescence.  Some echoes may happen soon - it's a bit 
surprising that they haven't happened yet.  On the other hand, it's the 
first outburst ever, so maybe it's erroneous to "expect" the echoes. We 
are getting superb coverage from Josch Hambsch, and good support from 
Berto and Bob Rea.  Keep it up for a few weeks; the superhumps are going 
strong and flashing some interesting (though not yet decipherable) effects.

A popular northern star this season has been RX2133+51 ("Cyg"), with Tom 
and Enrique as the main perpetrators.  It's a DQ Her star, and the 9.5 
min pulsations come in like gangbusters (American expression).  But 
there's another strong signal, at 3.56 c/d.  This is a country mile 
(another American expression) separated from the known orbital frequency 
of 3.36 c/d.  It's the usual signature of a *negative superhump*.  But 
it's occurring in a binary of unprecedentedly long Porb (surprise #1), 
and it's FULLY COHERENT (in phase, not merely period) over our 500-day 
baseline (surprise #2).  This is fascinating to me.  We never have 
really studied the negative-superhump phenomenon for dependence on Porb 
- and maybe it obeys a quite different law from the positive guys.

This suggests a few new targets for study.  One is V378 Peg (PG2337+30). 
  It's bright, still in season, and Fred Ringwald's recent preprint 
seems to prove that it has negative superhumps.  And to suggest that 
they may be phase-coherent over a very long interval.  This is a 
wonderful target for us northerners.

TV Col (2A0526-328), a 5.5 hr binary reported to have a 6.3 hr 
photometric period.  (A + superhump, of course, but that would be mighty 
interesting at Porb = 5.5 hr.) We've made a few efforts to 
confirm/reject this period, but they haven't been decisive.  With better 
representation in the Southern hemisphere (hoping for help from Arto or 
Josch at the Atacama telescope farm), let's give it a really good effort 
now!

And one more, along these lines.  There's a fascinating paper by Schwarz 
et al. (2007, A&A, 473, 511) on RX J0524+42, also called "Paloma".  It 
seems to have a raft of periods around 2.5 hours.  Now this target is 
near V=17.5, but the amplitudes of variation are quite large (up to 1 
mag), and I think it qualifies as CBA-eligible.  At least for those with 
a little extra by way of aperture or courage.  This paper has been 
strangely ignored (by me, too)... but it's pretty damn fascinating! 
J2000 05 24 30.52, +42 44 50.4.

A few stars to retire.  (1) RX2133 - we have enough now.  (2) BY Cam - 
for about a month; we have GREAT coverage, from Enrique and Bob Koff, 
but we can postpone for 4-6 weeks, then resume to get a very accurate 
period (or [periods?). (3) RX0636+35 - also for 1-2 months, then resume 
to narrow down that period.

For DQ Her pulse maintenance, the good stars to do now are: DQ Her, 
IGR0023+61, V1062 Tau, and WX Pyx.  A touch more RX0704+26 would be nice 
too.

Can anyone get a time series on T Pyx yet?  Chop down those trees, and 
give it a try!

joe