[vsnet-alert 5811] CR Boo & V803 Cen campaign

[Joe Patterson <jop@astro.columbia.edu>]

                    CR BOOTIS and V803 CENTAURI

     We have started a photometry campaign on the helium dwarf novae CR
Boo and V803 Cen, designed mostly to trace the extremely rapid up-and-down
excursions of these stars.  Right now both stars are in "cycling states",
in which they go back and forth between about 13.4 and 14.6, with a period
somewhere in the range 18-24 hours.  Naturally this is a really awkward
period to study, unless you have observers spread around at various
longitudes.  Also, the nature of this variation is still not known; it
could be just a spectacularly short dwarf-nova recurrence period, or some
(other) kind of disk oscillation not yet found among the more familiar   
hydrogen-rich CVs.  For these reasons, we eagerly seek observations of
these two fascinating helium stars over the course of our campaigns (about
3 more weeks).

     The expected range of ~1.2 mag means that visual observers can
effectively contribute.  CCD observers who are able to obtain long time
series (sequential JD, delta-magnitude) photometry can do even better,
because such observations will accurately trace the sinuous waves in the
light curve, and also the small superhumps on a ~25-minute timescale that
are characteristic of these two stars.

     Can you join us in this enterprise?  The stars are at

          V803 Cen  13 23 44.51  -41 44 30.4  2000
          CR Boo    13 48 55.29  +07 57 34.8  2000

and charts with suggested (CCD) comparison stars are at the cba website
(http://cba.phys.columbia.edu/charts).  Unfiltered or V-band observations
are fine, and a different comp star is also OK as long as you identify it.
   
I'll be episodically sending out the processed light curve to campaigners,
and I hope you can join us!

         Joe Patterson  (for the CBA campaign)
         CBA-New York
         jop@astro.columbia.edu
         212-854-3276

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