[vsnet-alert 1447] DI UMa rises again

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

                         DI UMA ERUPTS

    The beginning of this dwarf nova's superoutburst was caught by
J. Kemp on January 31.3 UT, during a 11.3 hr observation.  The light
curve is at our website (http://vsnet.astro.columbia.edu/~cba).  Thus
the star should stay bright (15-15.5) and superhumping for the next
6-10 d.  We face a poor weather forecast in Arizona, and would love
to collaborate with CCD or photoelectric observers at other sites,
in order to track the superhumps.  By splicing together data from
several sites, we hope to overcome problems with cloud and daylight.
The superhump amplitude is usually about 0.15-0.20 mag, and the
period is about 80 minutes.

     With a favorable declination and meridian crossing now
occurring near local midnight, the star's circumstances are ideal for
an intense campaign.  Basically we want a time series, as long as
possible, of differential photometry with respect to any comparison
star you like (but the one 20 arcsec north of DI UMa is a nice choice).
Unfiltered or V-band data would be fine.  The star's 2000 coordinates 
are: 9h 12m 16.24s, +50d 53m 53.6s.  A chart is available at our website.

     If you can manage to get any data, we'd love to hear from you!
(Or even if you can't, but are just generally interested in the
enterprise.)
                                        
Joe Patterson, Jonathan Kemp
jop@astro.columbia.edu
jonathan@astro.columbia.edu

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