THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS 25 Birch Street, Cambridge, MA 02138 USA BITNET: aavso@cfa SPAN: cfa::aavso INTERNET: aavso@cfa.harvard.edu TeL 617-354-0484 FAX 617-354-0665 AAVSO ALERT NOTICE 197 (January 27,1995) OBSERVATIONS OF CATACLYSMIC VARIABLES FOR ASTRO-2, EUVE, VOYAGER, AND ASCA SATELLITES The NASA satellite Astro-2 is scheduled to be launched from the space shuttle on March 1, 1995. We have been invited to participate in this mission and play a key role in its success. Astro-2 is a follow up to Astro-1, which was launched from the space shuttle in December of 1990, and to which we made significant contributions in the observations of cataclysmic variables. The Hopkins Ultraviolet Telescope. (HUT), part of Astro-2, will be observing cataclysmic variables both in outburst and in quiescence during the mission, and for the first time, three other satellites - Extreme Ultraviolet Explorer (EUVE), Voyager, and the Japanese ASCA - will be observing these stars simultaneously with Astro-2 during these times. Thus, this will be the first time that cataclysmic variables will be observed simultaneously from x-ray through extreme ultraviolet and far ultraviolet to ultraviolet wavelengths. The instruments aboard the satellites are ideal for studying the structure and evolution of the disk and winds in dwarf novae through outburst, the boundary layer in cataclysmic variables, and the temperature, size, and accretion column of the white dwarf component of magnetic cataclysmic variables like AM Her. We have been asked to monitor closely the stars chosen for this mission and listed below, and to inform the astronomers involved as soon as any of these stars go into outburst. 0058+40 RX And 0409-71 VW Hyi 1247-28 EX Hya 0139+37 AR And 0749+22 U Gem 1813+49 AM Her 0207-63 WX Hyi 0804+28 YZ Cnc 1934+30 EM Cyg 0219+27 RW Tri 0814+73 Z Cam 2138+43 SS Cyg 0309-22 EF Eri The highest priority targets are VW Hyi, WX Hyi, and YZ Cnc, although the others may also be observed. We have been in communication with the astronomers involved with this mission for the past several months, and we have provided extensive observations for use in mission simulations. We will be giving the astronomers an update on the behavior of these stars on February 21. Please monitor these stars closely from February 13 to March 17, and call in your observations, using the charge-free number (800-642-3883) at AAVSO Headquarters, or send email to aavso@cfa.harvard.edu. Early observations are needed for the updates, and particularly after the satellite is launched on the shuttle on March 1. The day-to-day observations of these stars will be crucial to schedule the observations with Astro-2 and the other satellites. We will be in close communication with the astronomers from mid- February to the end of the mission. If you need charts for any of the stars below, please let us know, and we will send them to you at no charge. You, our observers, played a major role during the Astro-1 mission in the observations during the outburst of Z Cam. Through your early alerts and close monitoring, a very interesting set of observations was obtained on this star, in that astronomers detected forbidden oxygen VI lines that indicated a much hotter disk (see AAVSO Newsletter 8, July 1991). Your contribution to the forthcoming Astro-2 mission is even more important and is truly vital! Astro-2, EUVE, Voyager, and ASCA will be pointed to observe the stars that YOU inform us are in outburst or in quiescence, so your contribution is absolutely crucial, and your timely communications are anxiously awaited. REMINDER REGARDING OUTBURST OF 0749+22 U GEMINORUM Please continue to monitor U Gem closely, and call in or email your observations to AAVSO Headquarters when it goes into outburst, so that observations can be scheduled with the Hubble Space Telescope for the quiescent period following the outburst. The answering machine at AAVSO Headquarters is on during nights and weekends for your convenience. Many thanks for your observations and vital astronomical contributions to variable star research. Good observing! Janet A. Mattei Director