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Alert Notice 231: Rare bright outburst of 1137+72 DO Draconis (= YY Draconis)

THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
25 Birch Street, Cambridge, MA 02138 USA
INTERNET:  aavso@aavso.org
Tel. 617-354-0484       FAX 617-354-0665

AAVSO ALERT NOTICE 231 (October 17, 1996)

RARE BRIGHT OUTBURST OF 1137+72 DO DRACONIS (= YY Draconis)

We have been informed by G. Poyner, Birmingham, England, that the dwarf nova
cataclysmic variable DO Dra has gone into a bright outburst, and was at visual
magnitude 12.7 on Oct 16.784 UT.  T. Vanmunster, Landen, Belgium, confirmed the
outburst with his CCD observation of magnitude 12.0 on Oct 16.787 (CVC Circular
112).

Other recent observations of DO Dra include:  Oct 15.7660, <14.3, G. Poyner,
Birmingham, England; 15.824, <12.4, M. Gill, Solihull, England; 16.956, 11.1,
Gill.

This star has been in the AAVSO observing program since January 1984.  Bright
outbursts of DO Dra have been recorded in the AAVSO International Database in
March 1988 and September 1990, when the star reached magnitudes 10.1 and 9.7 at
maximum, respectively.  The duration of each of these two outbursts was five
days.  Several minor brightenings, when DO Dra reached 14.0 - 14.5, have also
been reported (see AAVSO Alert Notice 184).

The infrequency of bright outbursts suggests that DO Dra might possibly be an
SU UMa type dwarf nova, although the durations of the previous two bright
outbursts were too short to qualify them as superoutbursts.  Please monitor the
current outburst of DO Dra closely.  Observers with CCDs are strongly
encouraged to observe this star every 3 to 5 minutes for several hours in
search of small-amplitude oscillations or superhumps, the signature of SU UMa
stars.  Such photometry would also be very valuable to help ascertain the shape
of the light curve of the bright outburst maximum and decline, information not
well known because of the scarcity of observations during bright outbursts.

Accompanying is a revised AAVSO preliminary "e" scale chart of DO Dra.  Please
use this chart to observe DO Dra and report your observations to the AAVSO by
email, fax, or telephone.  Please note that there are several different sets of
comparison stars for DO Dra in circulation, so it is *essential* to indicate
the source, the issue date, of the chart and the comparison stars you have used
in making your magnitude estimates. Without this information it will be
impossible to have a homogeneous data set for DO Dra.

CHARTS AVAILABLE ON AAVSO FTP SITE

Chart links are obsolete; 11/2013 create charts using VSP at http://www.aavso.org/vsp

Electronic copies of the revised AAVSO chart of DO Dra mentioned in this Alert
Notice are available from our FTP site:

              ftp.aavso.org (198.116.78.2), in /pub/alert231

The chart may also be accessed through our Web site at the following address:

                         http://www.aavso.org

The answering machine at AAVSO Headquarters is on nights and weekends for your
convenience.  Please call our charge-free number (800-642-3883) to report your
observations.  If you are cut off when you telephone in your observations,
please wait a few minutes and call back to complete your call.  We have learned
that if someone calls to leave observations on the answering machine and while
they are speaking someone else calls, the first person may be cut off.  We
also encourage observers to send observations by fax to 617-354-0665 or by
e-mail through the Internet to observations@aavso.org.  We would appreciate it
very much if you would report your observations in Universal Time.

Many thanks for your valuable astronomical contributions and your efforts.

Good observing!

Janet A. Mattei
Director

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