(cba:news) GW Lib, SDSS1339+48, V4743 Sgr, and OT2138+26

Joe Patterson jop at astro.columbia.edu
Sat May 22 00:58:40 EDT 2010

Dear CBAers,

Time for some spring cleaning. Unless it goes steadily faint again, we 
can leave CR Boo for the season.  The campaign on OT2138+26 is going 
well (good coverage from Bill Stein, Tom, Bill Goff, and Enrique)), but 
the unfavorable placement of Pegasus in May creates problems.  We 
*really* could use some coverage from other longitudes - while hanging 
onto our existing ones!

Helena (Uthas) is still at Kitt Peak, along with several Columbia 
students, and is carrying out a campaign on a CV with a pulsating white 
dwarf: SDSS1339+48 ("UMa" in Downes catalog).  I would *love* to get 
some CBA coverage on this star.  It has a very long period 
("superorbital"), which probably will require multi-longitude 
observation to break the alias.  In addition, the pulsations are 
probably stable enough to reveal fine-structure effects (beating of 
closely spaced signals, etc.) if we could get such data.  I think that 
at least some CBAers can get good data on this 17.5 mag star - the light 
curve will be no beauty, but the power spectrum should show the 
pulsations.  We especially want European coverage, of course!  Let's see 
if Arto or Enrique rise to the challenge.

I admit the waxing Moon is no friend to this enterprise.  But periodic 
signals have a way of shining through... and anyway, our interest in 
this star will go on at least a few weeks.

In the same vein, we're also campaigning on GW Lib, brighter at 16.5. 
Clobbered by the Moon on certain nights because of its zodiacal 
location, but happily southern and brighter.  An excellent target for 
southern telescopes, for two reasons: the pulsations, and the mysterious 
"2.1 hour" signal of unknown origin.  Our previous campaign showed that 
it's actually a 4.2 hour signal (with most power at the first 
harmonic)... now we want to go on it a while to test for stability. 
These mysterious superorbital periods are still a total mystery in CVs 
(about 10 of them).

Finally there's V4743 Sgr.  We need one more season on this, or possibly 
just one more month, to complete our study over an 8-year baseline. 
It's back - I hope some southerners can help us wrap this one up.

If you'd like to receive any of our data on these various targets, 
please ask!  We don't yet have any automatic system for this, but are 
developing one.  In the meantime, try the old-fashioned way!


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