Report from the trenches...

From: Joe Patterson <*jop_at_astro.columbia.edu*> Date: Mon, 27 Sep 2004 18:45:48 -0400 (EDT) · jop_at_astro.columbia.edu

Dear CBAers,

Well, actually it's the mountaintop... but you know what I mean.  In a
long streak of unrelentingly beautiful skies, the body feels like it has
been beat up and left in the trenches.  Good for the soul, though, and
good for science.

We (Jonathan is here with me) have been observing with the MDM 2.4 m on
Kitt Peak.  We've spent most of our time on HS2311+3905, a strange 16th
magnitude CV that is a cornucopia of periods, mostly noncommensurate and
apparently independent.  There's something at 3.1 hours, 1.35 hours (very
likely orbital), 23 min, 11 min, 5 min, and 1.1 min - plus a slew of
harmonics.  Gracious!  And a daunting challenge for interpretation.  Some
of these signals are likely to signify pulsation of the underlying white
dwarf, and maybe even ALL of 'em are.  Anyway, those matters are far down
the road.

Our run ends tomorrow.  This object will be a challenge for you... but so
far, Tonny and Lew have submitted data sets that appear to be pretty good
- definitely revealing the larger amplitude signals.  It will very
important to track them through the (northern) fall, to see which ones
have long-term coherence.  Nice target for scopes of sufficient aperture.
Open wide! - leave those filters safely wrapped inside their shipping
containers.

But ASAS0025+12 is surely the star of the season.  We still have almost no
data from half the planet (Europe, Africa, Asia) - but with many
consecutive nights of 11 hour coverage, alias problems have melted away
and the power spectrum revealed in all its glory. Probably second only to
WZ Sge in the quality of its time series.  Like all DN, the light curve is
dominated by very strong signals at the superhump frequency wsh and its
harmonics.  But because the coverage is so good, you can also see
"sidebands" flanking all the superhump frequencies - i.e. at wsh+W,
2wsh+W, 3wsh+W, etc., where W is a constant interpretable as the
precession frequency itself (so wsh+W is the underlying orbital
frequency). I consider this really, really valuable - because when you
know both the superhump and orbital periods, you can learn the mass ratio
of the binary (the difference between Psh and Po is a measure of the
secondary's gravitational perturbation).  One of the hardest things to
know about a CV!

The perpetrators have been mostly the usual suspects: Lew, Major Tom, Bob
Rea, Dave Messier, Brian, Donn, and some potshots from Arto Oksanen, Peter
Nelson, Alon Retter, Michael Koppelman, Gianluca Masi - plus really
beautiful data from Michael Richmond and Anthony Kroes.  If you've been
observing the star and would like to receive the full data, ask.  Within a
few weeks we plan to institute whereby you can retrieve the raw data
yourself, with a password (Jonathan will announce this when it's ready).
If you'd like the processed data now, just write me.  This has been
spliced, and normalized to acount for observatory differences.  It's the
best version to use for period-finding.  ASAS0025 is a nice object for
learning about period-finding, because it's kind of... well, GAUDY!

Should be a good target for at least a week, maybe much longer.
Southerners, don't be scared by the declination - we can really use
coverage from Australia and Africa.

Berto and Greg Bolt have obtained enough data on DV Sco to suggest
superhumps, but the star sets so early that period-finding is tricky.
Southerners able to observe this star VERY SOON (within a few days I hope)
may be able to get enough coverage to patch together a global time series
and determine a unique period.  Try!

LD 317 has come back into the sky.  We had a good campaign last year,
revealing signals at Porb and two fast periods near 35 minutes.  It's
getting a little crowded out by the celebrities now transiting near local
midnight... but we sure as hell want to do a good campaign on it this
year, and this could be a good time to start.

Don't have time to discuss other stars.  Getting dark soon... and
naturally it's clear.

joe