(cba:news) new at the cba web site

Jonathan Kemp jk at cbastro.org
Tue Aug 21 16:23:34 EDT 2001

Dear CBAers,

I just wanted to let you know about some new features that we've recently
introduced at the CBA web site.

First, after introducing an approximately real-time display of recently
submitted data sets, we have now introduced a similar automated sorting of
data sets by station (for full-fledged, frequently-contributing members)
and by object!  The latter is still a bit under development with a few
objects yet to be added, but please feel free to take a look.  If you wish
to resubmit past data to the archive, please contact me (Joe and I have
dug out our much of our old CV photometry dating back to late 1997 and
have entered it into the archive).

Second, we have inaugurated a product review section that features
articles by CBA members on those products which might be of greatest
interest to our members.  The first feature in this section is a piece by
Tonny Vanmunster (CBA Belgium) on the wonderful new AIP4WIN software which
may be an appropriate answer for future CBA data reduction needs.  We also
eagerly solicit additional contributions to this section on other products
which might be of interest to other CBA members (Meade/Celestron
telescopes, SBIG/Apogee CCDs, The Sky, CCDOPS, MaxIm DL, MuniPack, EZPhot,
Hellier's book, etc.).

Third, we have included a preprint for the recently submitted article on
HP Librae (abstract below).

Please pay us a visit and let us know what you think!


CBA Hilo


Superhumps in Cataclysmic Binaries. XXI. HP Librae (= EC 15330-1403)

J. Patterson, R. Fried, R. Rea, J. Kemp, C. Espaillat, D. Skillman,
D. Harvey, D. O'Donoghue, J. McCormick, F. Velthuis, S. Walker, A. Retter,
Y. Lipkin, N. Butterworth, P. McGee, & L. Cook

Publications of the Astronomical Society of the Pacific
submitted, August 2001

We report photometry of the helium-dominated cataclysmic variable HP
Librae during 1995-2001.  The main photometric signal varies between
1118.89 and 1119.14 seconds, on a timescale of a few years, and displays a
waveform characteristic of "superhumps".  After subtracting the main
signal, we found a weak residual signal at 1102.70+-0.05 s, which we
interpret as the underlying orbital period of the binary.  The full
amplitude of this putative orbital variation is just 0.005 mag, the
weakest orbital signal yet found in a CV.  The 1119 s signal of HP Lib is
a superb match to the well-studied 1051 s superhump of AM CVn, the "mother
of all helium CVs".

The superhump shows no change in amplitude or waveform on any timescale,
and no essential change in period on timescales shorter than ~3000 cycles.
Such great stability makes the star a promising test case for detailed
studies of the underlying spiral structure in the disk, the likely cause
of superhumps.  Comparison of orbital and superhump periods for the family
of AM CVn stars supplies evidence that these stars are evolving towards
longer orbital period.

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