(cba:news) fuel for borealites, mainly
jop at astro.columbia.edu
Mon Oct 24 07:45:53 EDT 2011
Nearly all northerners are excluded from the BW Scl excitement this
month (and next). But the nights are long and clear in many parts of
the northern CBA world, so here are some juicy targets.
Two prime evening guys. Now that BW Scl has erupted, I'm thinking again
of GD 552 = Cep 1. A very, very similar star, also with no eruptions in
history. Same quiescent brightness (16.6). BW Scl is extra-tantalizing
because it shows MANY periodic signals in quiescence (probably most due
to WD pulsation). But we haven't done a really good study of GD552 -
let's do it now! It's still in prime position, and should reward very
Plus RX2133+51 = "Cyg". We've had very good coverage the last two
years, started by David Boyd, and fervently continued by Enrique, Tut,
Tom, Bob Koff, Etienne Morelle, and Jim Jones. I just finished the
analysis, and behold, what strange beast is slouching towards Cygnus!
It's a fine DQ Her star, beautiful detection and 9.5 minute pulse
timings, sideband pulses at w-W, all very nice. Five year baseline now
for Pdot studies. There's an "orbital" signal too, and it's at 6.729(1)
hours. Uh-oh... the "known" Porb, from spectroscopy and the separation
between the spin signals, is 7.17(2) hours. The nature of the new
signal is unknown, but it's emphatically present in 2010 and 2011, and
there's a tentative indication that it maintains phase coherence during
the two years (together, not just separately). Coherence would make it
a little harder to just mutter "negative superhump". (Although, at this
point, it *is* what I mutter.)
Unless memory fails me, it's the first superhump which has shown up at
such long Porb. We've definitely been biased in our searches towards
stars which "should" show superhumps. It's a lot harder to work on the
long periods - but it may well be a good choice as next-world-to-explore.
Two morning stars I highly recommend are RX0636+35 (Aur) and RX0704+26
(Gem), both fine DQ Her stars needing work for pulse maintenance. They
too have long Porbs, and that's food for thought.
Under good conditions, VY Scl is also food for thought. It's now in a
faint state (17). Our several studies at maximum light were quite
unproductive; but there's a pretty good chance that this star will
finally cough up its secrets at quiescence - if the (mainly southern)
humans can take care of their business. Long time series needed, to
cover the range of periods that might be expected.
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