october observing

From: Joe Patterson <*jop_at_astro.columbia.edu*> Date: Thu, 17 Oct 96 08:33:25 EDT · jop_at_astro.columbia.edu

Hi CBAers,                                              Oct 17, 1996.

     Update on the October observing campaign.  The target stars have
been S-193 (=Peg-2) in the evening and WX Ari in the morning.  We have
had a streak of good weather at Braeside Observatory (AZ), and I've
just analyzed the data. WX Ari shows a large (0.35 mag full amplitude)
signal at 0.1395 d, but that is inconsequentially different from
Porb (obtainable from Pspec).  So now I think this star is of only
minor interest to us.  I'm taking it off the "campaign" list.  A hit
every few weeks will enable us to track Porb to high accuracy, which is
worth doing.

     The news on S-193 is more interesting.  The light curves are very
complex, and I only hope that we can patch together enough data from
disparate longitudes to really unravel them.  It looks to me like the
main photometric signal occurs at 0.1779 d, with another probable
signal at 19 min (maybe coherent, more likely not).  But there is a lot
of other hash too, around Porb, Porb/2, Porb/3.  Looks a lot like BZ
Cam.  I think it is possible that we will be able to sort this stuff
out, if we can do a good job over the next month (our last shot for the
year).  The Braeside observations have used a V=14.19 (B-V=0.88) comp
star 1.5 arcmin NE of the variable, while the European observations
have used a 12.0 mag star (GSC 1134 736) about 5.5 arcmin SE of the
variable.  Either star is OK, select one based on your aperture and
field size.  Try to get long time series on this star in the evening
sky.

     As most of you know, YY Dra has erupted.  We are pow'f'l curious
to know about periodic signals at 4.5 min, 9 min, and around 4 hrs
(Porb).  The timing could hardly be worse (spending all night below the
pole) -- but because these outbursts are quite rare, it would be
awfully nice if we could jump to action!  I think this is top priority
if you can get it; short integrations are best 'cause of the 9/4.5 min
pulsations known to be present at quiescence.  I recommend the V=11.84
(B-V=0.52) comp star 90" N (and slightly W) of the variable.

     At this moment, it looks like we might not get anything from North
America.  Dave Harvey is down for repairs, Bob Fried goes clunk (well
his telescope anyway) at that dec, and Dave Skillman is afflicted with
a mix of mechanical and horizon ills.  Europe is more promising.  Japan
would be really great and would extend the longitude range wonderfully.
Anyway the enterprise is a most worthy one, and do what you can.

     Other targets.  The season has definitely ended on RX1940-10.
V1974 Cyg definitely needs a few potshots to maintain phase through
about December 1.  FO Aqr and AO Psc have received practically no
attention this year and are getting lonely.  BG CMi has now returned to
the morning sky and could very much use a couple of early-season
visits.

     Now that WX Ari has been debunked, I think it's good to go after
another SW Sex star.  I recommend AY Psc (in Downes and Shara; notice
there's just one really obvious comp star, NW of the variable).  It
eclipses, and hences offers a geometrical diagnostic of the origin of
the superhump light (if we find superhumps).  DW UMa, another eclipsing
SW Sexer, was so incredibly interesting last spring (negative superhump
and large-amplitude manifestation of the precession itself) -- let's
see if we can find a fall partner for it.  So I think this should be
our standard morning target now - or even all night - assuming you
can't observe YY Dra, which I imagine is true for most people.

     Oh yes, one more thing.  AH Eri.  Too faint (17-18) at quiescence,
but would be very interesting to study in outburst.  Juicy reports of a
42 minute period.  A close watch on this guy would be nice.

Best o'luck!

                 joe