UU Aqr and Z And, New Heroes

From: Joe Patterson <*jop_at_astro.columbia.edu*> Date: Thu, 14 Sep 2000 08:27:41 -0400 (EDT) · jop_at_astro.columbia.edu

                                                             9/14/2000

Dear CBAers,

     Reports on the company campaigns first...

     DV UMa and IY UMa both coming out in Dec 2000 PASP.  Final copies
up on the web within a week, replacing the first versions (no big
changes though).  Copies in the mail to collaborators today.

     V751 Cyg submitted to PASP a few weeks ago, waiting for referee.
Beautiful standard-issue negative superhump.  Some possibly interesting
results on flickering.  Up on the web shortly.

     UU Aqr is a roaring success.  The 1998 campaign gave a surprising
result, with superhumps at a period apparently 16% longer than Porb.
That was a record (the old record was 10%).  But the signal was
somewhat weak, drifted in frequency, and possibly subject to aliasing
(the campaign was almost entirely from NZ, with Marc Bos, Stan Walker,
and Bill Allen).  Ergo, we needed more data.  All the more so because
this was a (candidate) *positive* superhump in a long-period eclipsing
system, and eclipses often enable us to learn the mass ratio from
independent evidence.  For years I've been trying to establish an
empirical correlation between epsilon (the fractional period excess of
Psh over Porb) and the mass ratio.  I think I've got it for small
epsilon, but my calibrators run out at Porb=2.06 hrs - so great is my
zeal to obtain a point at Porb=3.9 hrs!

     The response to the 2000 call for UU Aqr data was fast.  Bob
Fried, Lasse Jensen, and Lew Cook sprang to action, no surprise there.
So did Fred Velthius, Jenny McCormick, and Robert Rea (CBA-Pakuranga
and CBA-Nelson); these Kiwis are less well known to our group, but have
been stunning me all year with the quality and quantity of their data.
So did Neil Butterworth, finding breaks in a long cloudy spell in
Australia.  And Jerry Solomon, a first-time CBAer who works at the
"Center for Computational Biology" at Caltech -- I dunno what that is
but it sure sounds interesting (I hope he will tell us in a Fall
newsletter -- yea, verily, it will happen).

     When I spliced the first 9 days together and removed eclipses, an
obvious positive superhump appeared with eps = 7%.  This vaults UU Aqr
into top priority for the next 30-40 days.  We need that time to
increase frequency resolution and look for other stuff (higher
harmonics, frequency drift, possible orbital and negative-superhump
signals).  At 13th mag and near the celestial equator, this star should
receive a lot of attention from us.

     I still dunno what to think of the 1998 result with eps = 16%.
It may be interesting that this signal is displaced in frequency from
nu-orb by exactly (within errors) twice the displacement in 2000.  On
the other hand, it may just signify that I spend too much time punching
calculator buttons.

    Oh yeah, the AO Oct campaign is also (I think) over.  Data from
Marc, Fred, and Jenny defined Psh pretty well, and our South African
friends (Brian Warner, Claire Blackman, Patrick Woudt) got both
quiescent and superoutburst photometry.  Should lead to an epsilon for
this interesting star.

    Other campaigns in progress.  We need pulse timings (2-3 hr
observations, very careful absolute timing please) of the DQ Her stars
that are in season now (AO Psc, FO Aqr, V709 Cas, V405 Aur).  And we
need frequent shots at Cep 1 = GD 552.  No eruptions in history yet for
this star, but any definition of outburst activity or periodic signal
would be precious.

    Finally there is Z Andromedae.  Jeno Sokoloski obtained a large
batch of outburst photometry 3 years ago, and found stable 28 minute
pulses in the B light curve.  It just went up again, to 10th magnitude,
and will probably stay bright throughout the season.  Since most of you
observe unfiltered with red-sensitive CCDs, I was somewhat doubtful
that this weak signal would be detectable.  But Dave Skillman's first
night gave a reasonably clear detection.  So.... for northern
smallscopers, Z And is a very good target throughout the fall.  Watch
for saturation though.  If you happen to have a B filter, that would
probably give you an advantage (Bob, this would be a good target for
BVI or some such thing, especially since you can get to 1% in such a
short time).

    That's the lot.  Pretty good September menu.  In a few weeks we'll
start a strong push for VY Scl, which is now running around 12.8 and
which is a fine candidate for superhumps.  Any australites inclined to
get an early start, that would be mighty nice.

    By the way, Jonathan visited New York this week and tuned up all
our CBA machinery.  Things work a lot better now!

          joe