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 242 (November 3, 1997) SUPEROUTBURST OF 2110+13 EF PEGASI We have been informed by Thomas Burrows (Novato, CA) and Patrick Schmeer (Bischmisheim, Germany) that the dwarf nova type (SU UMa subclass) cataclysmic variable EF Peg is in superoutburst, as indicated by the following observations: Nov 1.93 UT, <13.0 (P. Schmeer); 2.1868, 11.4 (Burrows); 2.713, 11.1 (Schmeer); 2.750, 10.8 (Schmeer); 2.760, 10.7 (Schmeer); 2.835. 10.7 (Schmeer); 3.0771, 11.2 (G. Hanson, Cave Creek, AZ); 3.1604, 10.9 (R. Royer, Lakewood, CA); 3.1750, 11.2 (Hanson); 3.1951, 11.6 (Burrows); 3.2076, 11.3 (Hanson); 3.779, 11.2 (E. Broens, Mol, Belgium); 3.795, 11.3 (E. Muyllaert, Oostende, Belgium). The last two superoutbursts of EF Peg were in October 1991 and January 1995 (see AAVSO Alert Notice 196) and they were both first detected by P. Schmeer. Both superoutbursts lasted about three weeks. The orbital period of the system was estimated to be 2.05 hours from the observed superhump period of 2.09 hours during the 1991 superoutburst (see S. Howell et al. 1993, P.A.S.P., 105, 579). EF Peg has a close companion about 5 arcseconds away at position angle 305 degrees. In making a magnitude estimate, observers are recommended to use high magnification and to be particularly careful of this companion. When reporting observations of EF Peg during outburst, please indicate whether your estimate is a combined magnitude or not. Please monitor the current superoutburst of EF Peg, using the accompanying "f" scale (5"/1mm) AAVSO preliminary chart, and report your observations to AAVSO Headquarters. This chart has been been posted on our ftp site; see below for details. When reporting observations please indicate the source and the date of the chart, as well as the magnitude of the comparison stars used. Observers, particularly those using CCDs are encouraged to search for superhumps (small amplitude, periodic oscillations during superoutburst) by observing EF Peg every three to five minutes for several hours. Please report the time of your observations to four decimal places of the day. Also posted on our ftp site is AAVSO Alert Notice 196 which gives details of the Jan. 1995 superoutburst of EF Peg, together with the history of the comparison star magnitude sequence of the AAVSO chart. We congratulate Tom and Patrick on their detection of this outburst of EF Peg! REQUEST TO MONITOR 0749+22 U GEMINORUM FOR OBSERVATIONS WITH EUVE and RXTE We are collaborating with astronomers from Lawrence Livermore National Laboratory in the observations of U Gem in an exciting observing program that will involve the Extreme Ultraviolet Explorer (EUVE) and the Rossi X-ray Timing Explorer (RXTE). These satellites have been scheduled to observe U Gem as a target-of- opportunity object as soon as it starts to go into its next outburst. The investigating astronomers have requested that we inform them immediately when U Gem starts to brighten so that they can cover the rise to maximum with the satellites, particularly with the EUVE which observed U Gem at maximum during its December 1993 outburst. The aim in the forthcoming observations is to observe the rise to maximum in order to fill in the gap. Thus, the early notification of the outburst is crucial. Please monitor U Gem closely, and inform us immediately by phone, fax, or email when it starts to brighten, i.e. becomes brighter than 13.5. Once U Gem goes into outburst, please send in your observations daily so we may keep the astronomers informed of the star's behavior. The success of the observing run 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 chart of EF Peg mentioned in this Alert Notice are available from our FTP site: ftp.aavso.org (198.116.78.2), in /pub/alerts/alert242 or ftp.aavso.org (198.116.78.2), in /pub/charts/peg/ef_peg 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. We also encourage observers to send observations by fax to 617-354-0665 or by e- mail through the Internet to observations@aavso.org. Many thanks for your valuable astronomical contributions and your efforts. Good observing! Janet A. Mattei Director