(cba:news) Nova Pyx 05

[Joe Patterson]

Dear CBAers,

Oops, I've gotten very sluggish with messages!  Been writing up some of
our work for final publication -- of which, more in the next note.  Here I
wanted to advise on Berto Monard's discovery of superhumps in the newly
reported "nova" in Pyxis. Namely, at

9 18 58
-29 42 36     (2000)

Sorry I do not have a more accurate position.  Can anyone provide one? And
Berto, can you post a picture of the field?  Reportedly it is close to
(possibly coincident with) the northern component of a close double.

The 4 hour light curve Berto sent me shows pretty much textbook
superhumps, so this must be a newly recognized dwarf nova -- with P~0.063
days.  It's about 13.4, with about 0.1 mag superhumps.  Very, very
tempting target for immediate, long, and energetic coverage with
time-series photometry!  Mainly for southerners, of course, but I hope
some southern USA people can jump in there too, because they fill an
important gap between Africa and AU/NZ.

The main southern target has been QU Car.  Time to put it to bed for the
season.  Although it's a bright star, the time-series analysis is tricky,
because the long Porb (11 hr) means that the most likely timescales of
variability are convolved with atmospheric extinction effects.  This can
be separated out with care, but it'll take a couple months to see what we
have.   he usual southern mainstays have kept the faith on this: Berto,
Bob Rea, Jennie, Bill Allen, Tom Richards, Peter Nelson.

I've just submitted a long paper reporting observations of several stars,
spanning about a thousand hours.  This was an exciting thing to finish --
not only because it represents so much work (of yours), but because it
finally achieved a breakthrough I've been groping for since 1998 (at
least).  Namely, to establish a CV secondary-star mass-radius relation
through observations of superhumps.  The idea is this.  Superhumps come
from precession, and precession is driven by the gravitational force from
the secondary.  So the precession *rate* gives information on the mass of
the secondary... and the orbital period separately gives the density of
the secondary, so you get out a mass-radius pair.  You have to *calibrate*
the relation since none of the objects involved (secondary, disk, white
dwarf) are just point particles.  But that's what I've been trying to
do... and I think I finally succeeded.

It's a big collaboration, with these CBA authors: Harvey, Fried, Rea,
Monard, Cook, Skillman, Vanmunster, Bolt, McCormick, Krajci, Jensen, Gunn,
Butterworth, Foote, Bos, Masi, Warhurst.  Mostly CBAers from the 1998-2001
era - since these observations have been ripening on the vine for a while.
Jonathan will be sending paper or pdf copies to authors in a few days (I
think).

More general CBA note to follow in a few hours.

Remember: NOVA PYX!  (really a dwarf nova, but I like that name...)

joe