THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS 25 Birch Street, Cambridge, MA 02138 USA INTERNET: email@example.com WORLD WIDE WEB: http://www.aavso.org Tel. 617-354-0484 FAX 617-354-0665 AAVSO ALERT NOTICE 241 (October 10, 1997) REQUEST TO MONITOR 2138+43 SS CYGNI FOR OBSERVATIONS WITH HST, EUVE, AND RXTE 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. CHARTS AVAILABLE ON AAVSO FTP SITE Electronic copies of the AAVSO charts of SS Cyg mentioned in this Alert Notice are available from our FTP site: ftp.aavso.org (18.104.22.168), in /pub/alerts/alert241 or ftp.aavso.org (22.214.171.124), in /pub/charts/cyg/ss_cyg The charts 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 firstname.lastname@example.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 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 email@example.com.