TY Vul and V1084 Her (RX1643+34)

From: Joe Patterson <*jop_at_astro.columbia.edu*> Date: Tue, 22 Jun 2010 16:10:12 -0400 · jop_at_astro.columbia.edu

Dear CBAers,

Richard Sabo just sent me a night of data on TY Vul - clear, strong 
superhumps at a period about 2 hours.  First time ever!  Fire at will.

Lots of northern dwarf novae peppering the predawn summer sky.  Best to 
pick one and stick with it, usually.  I'll try to keep everyone posted 
on the ups and downs of each.

Speaking of which... two other stars I failed to report on a few days 
ago.  A few of you (led by Bill Goff) have tackled our hardest target 
star, sdss 1339+48.  Bill's observations do show the pulsations, which I 
wondered about.  But they, along with the big-telescope data which 
preceded it, also show that the pulsations are not stable over baselines 
greater than a few days.  In fact, I suspect that this is true of all 
the GW Lib stars.  It means that long campaigns don't reap uniquely 
valuable rewards - revealing tiny rates of period change, for example. 
So let's put sdss1339 aside.

And for the same reason... let's resurrect V1084 Her = RX1643+34.  I've 
now analyzed all 2010 data on this bright novalike - and was somewhat 
amazed to find the negative superhump at *exactly* the same frequency as 
in 2001.  Generally one doesn't expect disk precession to show a good 
clock; none of the others do.  So now this object is (somewhat) uniquely 
curious, and it's bright enough to be a good target for maybe 2 more 
months.  Good northern evening target, or all night if you'd like a 
bright target.  Try to use star #2 of Mickaelian et al. 2002 as your 
comparison (V=12.97).

V1084 Her is near V795 Her in brightness, coordinates, and reason to 
observe.  You'll probably want to pick one or the other... but the more 
sure winner right now is V1084.

joe
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