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 239 (June 6, 1997)


OUTBURST OF 2328+48 Z ANDROMEDAE

The prototype of the symbiotic class of variable stars, Z And, is undergoing
an outburst, the first such since September 1985 (see AAVSO Alert Notice 78),
when it brightened to visual magnitude 9.1 and was above minimum for
approximately 290 days.  Following the 1985 outburst, Z And had shown
smaller-scale oscillations, until the beginning of the current outburst in
mid-May.  Recent observations of Z And reported to the AAVSO include:

Mar 29.8130, 10.8, M. Moeller, Timmendorfer Strand, Germany; 30.5063, 10.9,
G. Hanson, Cave Creek, AZ; Apr 8.4847, 11.0, Hanson; 11.8, 10.7, H. Marx,
Korntal-Munchingen, Germany; 16.4896, 10.8, Hanson; 21.1, 10.7, M. Fonovich,
Plomin, Croatia; 28.4694, 10.9, Hanson; May 8.4646, 10.9, Hanson; 9.110, 10.7,
G. Poyner, Birmingham, England; 11.117, 10.7, Poyner; 12.048, 10.7, Poyner;
14.042, 10.7, Poyner; 15.074, 10.7, Poyner; 20.071, 10.6, Poyner; 25.063, 10.6,
Poyner; 26.073, 10.2, Poyner; 26.358, 10.1, R. Modic, Richmond Heights, OH;
27.1667, 10.3, J. Bortle, Stormville, NY; 27.4458, 10.2, Hanson; 28.363, 10.1,
Modic; 29.4417, 10.0, Hanson; 30.045, 10.0, Poyner; 31.033, 9.7, Poyner;
31.093, 9.9, P. Schmeer, Bischmisheim, Germany; Jun 1.081, 9.8, Schmeer;
2.008, 9.8, Poyner; 3.4375, 9.8, Hanson; 4.364, 9.7, Modic; 6.342, 9.8, Modic.

The accompanying light curve of Z And shows 10-day means of the observations
in the AAVSO International Database for the interval JD 2445000 - 2450600
(January 1982 - June 1997).  11,854 observations contributed by 312 observers
from around the world were used to create the 10-day means shown.  We thank
each observer for his or her contribution.

Also accompanying are AAVSO 'b' and 'd' scale charts for Z And.  Please use
these charts to make your estimates of Z And and report your observations to
AAVSO Headquarters.  Please be sure to indicate the comparison stars you used.
If you use a non-AAVSO sequence to make your observations, be sure to identify
it when you report your observations.


REQUEST TO MONITOR 2138+43 SS CYGNI

Astronomers in England have informed us of their plans to observe the dwarf
nova cataclysmic variable SS Cyg with the BeppoSAX broadband x-ray satellite
when the star has its next outburst.  Our assistance has been requested to
monitor SS Cyg very closely and inform the astronomers as rapidly as possible
when SS Cyg begins to brighten, so they may trigger the satellite observations
in time to catch the star early in its outburst.

Please monitor SS Cyg closely, and telephone, fax, or email your observations
to AAVSO Headquarters, particularly when you see the star brightening, i.e.,
becoming brighter than visual magnitude 11.5.


REQUEST TO MONITOR 1813+49 AM HERCULIS

Astronomers in England are scheduled to use the x-ray satellite Rossi X-ray
Timing Explorer (RXTE) to observe the magnetic variable AM Her in its high,
optically bright state.  Since AM Her is presently in its low, optically faint
state, our assistance has been requested to monitor AM Her and to inform the
astronomers when the star returns to its high state.

Please keep a close eye on AM Her and telephone, fax, or email your
observations to AAVSO Headquarters, especially when you see the star
brightening to visual magnitude 13.8 or brighter.


CHARTS AVAILABLE ON AAVSO FTP SITE

Electronic copies of the AAVSO charts and light curve of Z And mentioned in
this Alert Notice are available from our FTP site:

           ftp.aavso.org (198.116.78.2), in /pub/alerts/alert239

The charts, along with the light curve of Z And, 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