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               Tel. 617-354-0484       FAX 617-354-0665

               AAVSO ALERT NOTICE 241 (October 10, 1997)


We are collaborating with astronomers from Lawrence Livermore National
Laboratory in the observations of SS Cyg in an exciting observing program that
will involve the Hubble Space Telescope (HST), Extreme Ultraviolet Explorer
(EUVE), the Rossi X-ray Timing Explorer (RXTE), and ground-based telescopes.
From now until the end of December 1997, these three satellites have been
scheduled to observe SS Cyg as a target-of-opportunity object during a maximum.
One of the goals of this observing run is to carry out a multiwavelength search
for very small-amplitude and very short-period oscillations of the white dwarf.

A similar campaign on SS Cygni was carried out in 1996 (see AAVSO Alert Notices
221 and 230 for information on this campaign).  This campaign and its exciting
results are summarized in the Annual Report of the Director in Volume 25,
Number 2, of the Journal of the AAVSO (in press).

In order to be able to carry out this year's campaign, the investigating
astronomers have requested that we inform them when SS Cyg starts to go into
outburst, i.e., brightens, and to continue to keep them informed throughout
the outburst so that the satellites may be scheduled to observe SS Cyg.
Certain satellite observations, due to scheduling constraints such as those
for HST, will or will not be scheduled based on whether the outburst is a
narrow or wide one, so timely notification of the onset of the outburst
and up-to-the-minute information on the behavior of SS Cyg throughout the
outburst are essential.

Presently, SS Cyg is at minimum, at approximate visual magnitude 12.0,
according to observations received at the AAVSO.  Its last outburst occurred
in September 1997, when it began to brighten on September 5, reached magnitude
8.3 on September 7, and returned to minimum on September 25.

AAVSO "b", "c", "d", and "e" scale standard charts for SS Cyg have been posted
on our ftp site; see below for details.  Those needing paper copies of these
charts should contact AAVSO Headquarters.

Please monitor SS Cyg closely, and inform us immediately by phone, fax, or
email when it starts to brighten, i.e., becomes brighter than 11.5.  Once SS
Cyg goes into outburst, please send in your observations daily so we may keep
the astronomers informed of the star's behavior and they may schedule satellite
observations.  The success of these observations very much depends on your
observations and the early alerts and continuous information we can provide to
our colleagues.


Electronic copies of the AAVSO charts of SS Cyg mentioned in this Alert Notice
are available from our FTP site:

  (, in /pub/alerts/alert241
  (, in /pub/charts/cyg/ss_cyg

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


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  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

Note:  We have received inquiries about the fact that we have not issued an
AAVSO Alert Notice since June.  The Alert Notice traditionally has been used
to inform the astronomical community of discoveries, requests for observations, unusual
stellar activity, and any item that requires the distribution of charts.
We continue to issue the Alert Notice to announce discoveries, requests for
observations, items requiring charts, and very unusual stellar behavior (such
as the outburst of a recurrent nova).  We began issuing the electronic
publication AAVSO News Flash last year to inform observers of stellar activity.
If you would like to subscribe to the News Flash (free of charge), please send
an email to

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484