(cba:news) stars for jan-feb

[Joe Patterson]

Dear CBAers,

Time for a revisit of targets...

It's a good time to take TT Ari off the rolls.  The star appeared to flash
its negative superhump throughout the season; the latter appeared for the
first time in 1997, and has presumably been going strong ever since.  This
long baseline will furnish the data for a nice study of period stability.
I had hoped that the positive superhump would accompany, which would then
give us the opportunity to study *simultaneous* period changes in both
types - this would be a very valuable discriminator among candidate
models. It'll take close analysis to be sure; but so far it appears that
the positive SH was too bashful.  V603 Aql is I guess the ideal star for
this experiment - but then becomes mostly a project for australites, since
the short summer nights hamper sensitivity in period studies (in Aquila)
for us northerners.  We'll fire that project up in May.

So exit TT Ari. Now let's talk FS Aur. The coverage has been really great,
led by Major Tom and Captain Bob.  I have a moderately long-term ephemeris
- 4 years - describing this mysterious 3.4 hour photometric wave
(mysterious since the binary period is 1.4 hours).  To my surprise, no
other signals appear in the time series - CVs are usually pretty sassy in
all the hard-to-understand structure in the power spectrum they shake at
you.  Anyway, I think the best strategy is to take it off the menu NOW,
then fire it up again for a brief reprise in March/April - the extra 60
days of baseline will establish the period sufficiently well to bridge to
next season, and quite possibly backwards to encompass all known light
curves.

So exit FS Aur too.  The star I'd like to promote for northern coverage
during the next month is BZ CAM.  This star tortured us in 1994, with its
3.2 hour waves which were not quite periodic yet not quite nonperiodic
either.  It's an all-night target for all northerners, and at magnitude
12.7 is suitably bright for everybody.  I hope we can get very long light
curves for a few weeks, which should be sufficient to decode even a fairly
complex spectrum of periodic signals.  I'm really counting on our friends
in Europe, since I know from experience that this star does not readily
yield its secrets to fixed longitudes!

Late in the night, for all hemispheres, HV Vir is the star of choice.
We're getting decent coverage, but limited by the season of course since
Virgo doesn't rise high enough till ~2 am.  Definitely a great target as
long as it remains decently bright - since it only outbursts once a decade
or so.

TX Col remains the best evening object for southerners.  Some very nice
data coming from Fred and Jennie, and also Greg Bolt from Perth (of TU Crt
fame... but in CBA quiescence for about 4 years).  Dave Buckley and his
crowd are doing photometry and spectroscopy from SAAO this week, so this
is absolute prime time to fill out the campaign with worldwide data.

Finally there's BH Lyn.  We tried this one 5 years ago, and got some
beautiful data but too limited in longitude to measure periods without
ambiguity (except for the eclipse period, which is obvious!).  Nicely
placed for northerners at 0822+51, and decently bright (14.5 out of
eclipse).  Bob Fried has gotten a few nights to kick off the campaign -
let's keep it going!

As for the other stars, let's:
(1) keep BK Lyn on the menu as secondary (good last target of the night
    once HV Vir gets too faint)
(2) kick RZ LMi temporarily off (people are having too much trouble with
    it)
(3) keep EC0511-79 on, in the hope that someone will actually observe it!

Good luck!


            joe