(cba:news) Stars for October

Joe Patterson jop at astro.columbia.edu
Wed Oct 18 08:34:01 EDT 2006

Dear CBAers,

Time to replace the menu of stars, as the Sun rolls eastward.

EF Tuc has received good coverage, mainly from Berto and David Moorhouse.
It looks like a tough nut to crack - there's a good candidate period near
3.5 hours, but this doesn't agree with well with last year's (indecisive)
result.  Some more analysis is needed here, so for now - and probably for
the year - we should sweep EF Tuc off the table.

The main northern star of the month has been IGR0022+61 = "Cas".  And a
damn interesting one too.  Lots of coverage from Bart Staels, Tom, Bob
Koff, and Dave Messier.  Beautiful 9 minute period in this star, with a
whopping 0.2 mag amplitude!   Almost certainly this signifies the white-
dwarf rotation, with the orbital period still not specified.  With ~40
runs so far this year and sufficient period constraint to count cycles back
to last year, it's time to quit.  Some more work on the analysis, and/or
a little spectroscopy, is very likely to yield Porb too.  (The early odds
favor 2.7 hours.)

I propose replacing these S/N principal targets with two others: BW Scl
and HS2331+39 = "And".  We've been getting occasional coverage of each...
mainly from Bob Rea and Lew Cook.  Now it's time to kick the campaigns to
a higher gear, and observe 'em pretty intensively during the present
dark run.  Both are bellwether stars for the theory of late evolution of
CVs.  And both somewhat challenging around mag 16.5 or so.

An easier northern target is V709 Cas, at mag 15.0.  Despite its very
favorable sky location, we've not had a lot of success with campaigns on
this star - it usually gets squeezed out by other priorities.  The star
has a fast period (313 s), and it would be great to time that signal over
the course of the next month or so.  You have to make sure your cycle time
(integration plus readout) is less than 90 s, and preferably less then
60 s.  AO Psc is a similar story, only here the star is essentially
equatorial (2254-03), and the star is a more relaxing V=13.6, P=858 s.
AO Psc is a star you can truly grow to love!

Finally I wanted to proffer a couple of odd stars which we have never
observed, and have hardly been observed by anyone.  These are "Cep" =
HS0229+80 and "Oct" = LB9963 = 0250-87.  Obviously bookended near the
celestial poles, which in part explains why they're unlikely targets of
equatorial telescopes.  Both about 14th mag, and both likely, but not
certain, to be CVs.  I dunno what they are - but you might be able to
find out.  If you're trying to figure out how to observe stars in such an
awkward place, consider the possibility of mis-aligning your telescope -
it'll cause some other havoc but might get the job done.

By the way I rolled the dice and got married (second time) two weeks ago.
Beautiful fall day in Central Park, very memorable.  I even wrote some
poetry for it and there was even astronomy - though nothing about variable
stars - in it.  Not as extreme as the first time, though, when I got
strangely fascinated by neutrinos while writing the ceremony.  Maybe that
was an omen for a marriage with very low cross-section.

Happy observing!


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