(cba:news) Stars of Aug-Sep 2000

[Joe Patterson]

Dear CBAers,

I'm finally back from many travels of summer 2000.  Here's some news of
target stars.

The DV UMa paper is scheduled for the December 2000 issue of PASP.  It
seems likely that IY UMa = Takamizawa will appear in the same issue
(possibly the next).  The paper on V751 Cygni (primarily 1999 data, some
1993 and 2000) will be submitted next week - it was a classic negative
superhumper, and we found all the relevant periods (P-orb, P-sh, and the
beat period which we identify as the wobble period of a tilted accretion
disk).

So much for northern stars.  We're ending the V751 Cyg campaign now,
mission accomplished.

The campaign on V1494 Aql is going very well, with lots of work from NZ
keeping aliases under great control.  But the star's waveform appears to
be stable, so I'm inclined to let it relax some more from its 1999
classical nova eruption, and revisit it again NEXT YEAR.  So those are the
two major campaigns going now - let's end 'em both.

The main star I want to promote now is V1315 Aql.  I think there's about a
month left in the Aquila observing season, and if we can get Europe-North
America-Australasia coverage, we can solve the outstanding quiestion.  In
the last campaign we got a nice superhump period, but cycle count
ambiguity made it uncertain whether it was positive or negative (the peaks
in the power spectrum were even-steven).  This can be resolved in 2 weeks
of vigorous campaigning.

And after that it'll be time for another campaign on UU Aquarii!  Decently
equatorial and bright stars for family fun.  I see that charts aren't
yet up on the CBA site (Jonathan, any chance?), but they're in Downes and
Shara (Feb 1993 PASP) and their coords are:

V1315 Aql = KPD 1911+1212  19 13 54.6  +12 18 2.3 decent looking comps to
                                                  the SW and NW
UU Aqr  22 09 5.8  -3 46 18.5   the close companion immediately to the
                                south (and slightly W) looks best

Finally the V803 Cen story is worth some exultation.  For 3.5 years I've
been working to measure Porb and Psh in this helium star.  We've had some
good campaigns but could just not get a precise measure.  I chalked
it up to bad luck - that this star, unlike all the others, just has too
sloppy a clock and hence resists efforts to nail down the period.  That
may be true to some extent, but the May 2000 campaign (data from Fred
Velthius, Jennie McCormick, Robert Rea, Maria Marsh, Brian Warner, Claire
Backman, and in the pipeline from Stan Walker) has clarified the
matter.  The superhump period is very close to Porb - just 0.4% longer.
This indicates a very, very low mass secondary - about 0.017+-0.005 Mo.
This is "the oldest known CV", where the secondary has been whittled down
to practically nothing (the pure helium content indicates that the
whittling has long ago reached the stellar core).

What a wonderful star mister Centauri has turned out to be!

Oh yes, there is also a far northern star I'd like borealites to start
watching.  This is GD 552, or "Cep 1" in the Downes and Shara catalog.
It's about 16.5, basically a dark-sky target, but virtually nothing - make
that nothing - is known about its photometric activity on long (eruption)
and short (nightly) timescales.  It's my other candidate "substellar"
secondary in the CV zoo.  It's better suited to Oct-Nov coverage, but who
knows when the star might erupt and/or shake some periods at us.

So - prime target V1315 Aql.  Happy non-trails... (background lilt of
cowboy music) to you, da-dah, da-dah, da,dah.


          joe