(cba:news) stars for february

Joe Patterson jop at astro.columbia.edu
Mon Feb 17 13:45:47 EST 2014



Dear CBAers,

  Three feet of snow outside now, in the Catskill Mountains.  Two in New
York City.  More coming tonight.  An amazing winter of snow and cold.
I've actually destroyed two snow shovels through overuse; I didn't think
it was possible to wear out a snow shovel.  A foot of ice on the astronomy-
department roof - and me trying to teach an observational astronomy class.
Tough on the old bones.

  I'm sure Joe U and all the upper-Midwest folks have similar stories.
But hope springs eternal, and let's overhaul our target menu.

1. V745 Sco has declined to show short-term variability, and it seems
likely that it's in the T CrB class, where we don't learn much from
photometry.  I could be wrong... but with so poor a sky position, I think
we should take V745 off the list.

2. HZ Puppis.  With Berto and Peter Nelson coming through (also Gordon Myers
and Bob Rea), the daily aliasing is now clear, and we have a great one-month
baseline.  A few runs scattered over the next two months will improve the
period and lay the groundwork for a long-term ephemeris (bridging the
always-troublesome yearly gaps).  But it needs no more than that... especially
since it competes with two more important old novae.

3. CP Puppis.  Time for another all-hands-on-board effort on CP Pup, for the
next three weeks.  A lotta nice data during the last two years, but the
conclusion from it is so unusual as to make me still uncomfortable (a new
kind of superhump - not orbital, not common, something new which doesn't
obey any known mathematical relation).  One more season would conquer
my discomfort!

4. T Pyx.  Back on the menu as a secondary target.  Maybe 5-10 nights from
now until May, when it disappears.  This should enable us to see whether 
the period now (post-eruption) has resumed its steady increase, or has
stabilized.

3. V902 Mon, a new DQ Her star.  We have great data, but it's all from
Enrique; we *really* need coverage from other longitudes!

4. V406 Vir.  Oh yes!  An excellent candidate for a period-bouncer - a
binary that has entered its final phase of evolution and is increasing its
P_orb.  Regardless of whether that's true, the star has a large-amplitude
signal with a period near 8 hours - far in excess of its 1.5 hour P_orb.
No one has a clue about what this is.  Is it stable?  Is it related in some
not-yet-measured way to P_orb?  These matters are *our* responsibility.
The star is mear magnitude 17, and thus within reach of most of our scopes
on good nights.  It's vital to get several longitudes in the act, too -
because the period is so long.  

5. AM CVn.  Easy target for CBAers.  We skipped 2013, and intended to make a
big push in 2014 to nail down the long-term P_orb change - which will be
compared with the predictions from gravitational-radiation theory.  (GR
expels angular momentum, and thus should shorten P_orb at a fixed rate.)
Now it's 2014, and let's do it.  AM CVn's light curve - pretty flat - wins
no prizes for beauty, but it does permit an accurate solution for the phase
of the orbital variation.

6. I've finished the long-term period solutions for several IPs, which
won't need any more coverage: BG CMi (thanks Shawn!), DQ Her, DW Cnc, V405
Aur, V418 Gem, V647 Aur.  Stars still needing that coverage are: V667 Pup,
EX Hya, WX Pyx, HT Cam, MU Cam.

7. In November we carried out major campaigns on BY Cam and RX0524+42
("Paloma") - and then left them to resume coverage in February (in order to
get the longest possible 2013/4 baseline).  Time to do so.

8. V355 UMa and ER UMa.  Enrique, could you clarify the status of these?
I'm inclined to recommend V355 UMa as a major target now, or starting in a
few weeks - whaddayathink?

   There's the menu.  I hope to see a whole bunch of you at the SAS/AAVSO/
CBA meeting in June!

joe p

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