(cba:news) Stars for February

Joe Patterson jop at astro.columbia.edu
Tue Feb 13 10:38:48 EST 2007

Dear CBAers,

   U Gem has dropped to quiescence now, there to remain, presumably, for
another 80 days or so.  I hope you can keep up occasional coverage for
the duration.  We'd like to study the hump eclipse and eclipse structure
throughout the inter-outburst cycle.  Because U Gem presents a uniquely
favorable geometry for studying the mass-transfer bright spot (spot
eclipsed but not the white dwarf and inner disk), this star can yield
detailed information on variations in hot-spot brightness and location.

   If you do try to keep vigil on U Gem, try to keep the integrations
pretty short (30 s?) to cleanly resolve ingress and egress... and I
recommend white light to raise signal-to-noise.  It's vital to use the
same comparison star always; but if you used one in eruption and it's
now too bright, then select another - making sure that you tell me.

   We do not, however, need nightly coverage on U Gem.  Just keep
hammering away a couple times a week... and then we'll increase the
frequency when we can smell the next outburst.

   In the south, Bob Rea has been keeping a solitary vigil on WX Pyx.
This is 17th mag but still a fine target for a 14", since it's a large-
amplitude DQ Her star.  We have a good ephemeris for 2007... and can now
wait about 60 days before obtaining a little late-season coverage to
jump the cycle count back to 2006 (and thereby secure it for a decade).
We can also back off RR Pic - Grant Christie got some data which will
secure its cycle count.
   The two top southern objects now are T Pyx - we only need a 2-3 week
observation, but it needs to be dense (a dozen long-duration time series
would be great!) - and Swift 0732-13 ("Pup").  Remember the latter?  We
had a very extensive campaign last year, and proved it's yet another DQ
Her star.  The light curve looks very flat, but this is caused by a very
nearby reddish star diluting the light of the CV.  This doesn't much harm
the rapid pulsation we seek to study, though.

   In the north, I recommend three of the new targets for this year:
Aur = RX0636+35
Gem = RX0704+26
Lyn = SDSS0804+51

All DQ Her stars which we've been endeavoring to follow closely during
the season.  The U Gem eruption forced a hiatus - but let's get back on
track.  They're all pretty close to 16th mag and have large-amplitude
fast pulsations.

   Olde Whiteface has wheeled out of the way again, Venus has reappeared
with gusto, and even Mercury popped up to say hello last week.  (Us
borealites haven't seen it much in the last decade; all the good
elongations are southern.)  Great time to be observing!


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