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 218 (February 16, 1996) MONITORING OF 1813+49 AM HERCULIS FOR INTERNATIONAL OBSERVING CAMPAIGN 1996 marks the 20th birthday of the discovery of AM Her, a magnetic cataclysmic variable. In celebration of this birthday an international campaign has been organized to obtain multiwavelength observations of AM Her using space-borne telescopes, such as the International Ultraviolet Observer (IUE), Hubble Space Telescope (HST), ROentgen SATellite (ROSAT), and Infrared Space Observatory (ISO), and possibly the x-ray satellite SAX, as well as ground-based photometric and spectroscopic observations. Dr. Boris Gaensicke, Universitaetssternwarte Goettingen, Germany, writes, "It would be very helpful, especially for the planning of satellite-based observations, to keep track of the optical magnitudes of AM Her. I would therefore like to ask if it would be possible to communicate [to] us on a weekly basis the brightness of AM Her." He continues, "AM Her shows an erratic variability, ranging from fluctuations in a few days to prolonged low and high states (up to years). This may seem in contrast to many of the dwarf novae displaying a more (or less) regular outburst pattern. "However, the variability in dwarf novae is thought to be mainly due to the dynamics of the accretion disk, while the variability in AM Her stars should reflect directly changes in the mass-transfer rate from the secondary. Alas, the behavior of AM Her is known in detail only at optical wavelengths, thanks to the effort of many amateur astronomers around the world. "When the last call for proposals for the IUE arrived, we thought that the last episode of this space veteran offers a unique chance for an extended UV monitoring of AM Her. Once this monitoring was decided, it became clear that any observation at other wavelengths would highly profit from the detailed knowledge of the accretion history in the system. "Up to now, we [have] obtained for this project weekly IUE observations from mid-February to mid-October, nine ROSAT pointings from up to the beginning of May, two sets of HST observations planned to cover low and high states, and infrared observations with ISO. We hope for additional coverage with the new Italian-Dutch x-ray satellite SAX, and for optical spectroscopy and photometry from several sites. "Some of our scientific aims are 1) to determine changes in the mass transfer rate over the nine months of IUE coverage; 2) to probe the thermal response of the white dwarf to changes in the accretion rate; 3) to search for contamination of the white dwarf by the metal-rich accreted material; 4) to derive the mass of the white dwarf and the secondary from radial velocity measurements; and 5) to determine the field structure and the accretion geometry..." In order to monitor AM Her effectively, Dr. Gaensicke and his colleagues have asked us to keep a close eye on this star and keep him informed regularly throughout the year, particularly as they are estimating the frequent IUE exposures. The first HST observations will take place this summer, and then they will wait until the brightness state of AM Her changes. Below is the preliminary schedule of IUE, ROSAT, and HST observations. IUE: Feb. 18, 25 Mar. 01, 06, 11, 16, 21, 26, 31 Apr. 05, 15 then UV monitoring continues at ~ weekly intervals up to mid-October ROSAT: Feb. 25 Mar. 06, 16, 26 Apr. 05, 15 plus some additional slots to be scheduled HST: July 1996 ISO: still to be determined SAX: still to be determined Please monitor AM Her closely, and communicate your observations regularly to AAVSO Headquarters. Presently, AM Her is in its high state, where it has been for several years. If its state changes, i.e., if it goes into its down state, please call in your observations immediately so that we may alert the astronomers involved in this international campaign. Accompanying are AAVSO preliminary 'd' and 'f' scale charts of AM Her. MONITORING OF THE CATACLYSMIC VARIABLE 0523-03 V1159 ORIONIS Dr. Paula Szkody, University of Washington, has asked our assistance in monitoring the interesting dwarf-nova type cataclysmic variable V1159 Ori during her coordinated campaign, which will involve three satellites, X-ray Timing Explorer (XTE), ROSAT, and IUE, and possibly the Extreme Ultraviolet Explorer (EUVE). V1159 Ori is a very interesting dwarf nova. From the superhumps that were observed in 1992 during a long outburst, and from the orbital period measured in 1992, it is classified as an SU UMa-type dwarf nova. However, it is a peculiar SU UMa star in that it has very frequent narrow outbursts (every two to three days) and also very frequent superoutbursts (about every 44.5 days). J. Bortle described the strange behavior of this star in the section titled "Bizarre Stars" in the Observer's Forum of AAVSO Newsletter No. 16, page 16, 1995. Accompanying is an AAVSO 'e' scale preliminary chart of V1159 Ori. Please monitor this star closely and telephone, fax, or email your observations to AAVSO Headquarters so we may assist Dr. Szkody. In addition, those who have email may send a copy of their observations to Dr. Szkody at szkody@astro.washington.edu. FLUCTUATIONS OF 0059+53 NOVA CASSIOPEIAE 1995 N Cas 95 (see AAVSO Alert Notices 213, 214, and 217) has been very closely monitored by our observers. This interesting nova showed a slow rise in brightness starting JD 2450022, from mean visual magnitude 8.7 to 8.5, then a much faster rise starting JD 2450059 from 8.5 to 7.2 on 2450068. This rise was followed by a rapid decline over 2450071 and 2450072 from 7.1 to 8.0. The slow decline continued to about magnitude 9.5 until JD 2450114. Since then the star has been brightening slightly and showing oscillations, as indicated by the following observations reported to AAVSO Headquarters by observers around the world: Feb 1.0118 UT, 9.5, J. Bortle, Stormville, NY; 3.0236, 9.2, R. Hays, Worth, IL); 3.81, 9.5, M. Zanotta, Milano, Italy; 3.9979, 9.4 (M.A. Komorous, London, Ontario, Canada; 4.0535, 9.4, W. Dillon, Missouri City, TX; 4.0646, 9.3, Hays; 4.883, 9.1, G. Poyner, Birmingham, England; 4.9340, 9.0, G. Gliba, Chagrin Falls, OH; 5.0264, 9.1, Hays; 5.0757, 9.0, Dillon; 5.1118, 8.9, P. Collins, Scottsdale, AZ; 5.9764, 9.2, Gliba; 6.0896, 9.3, Hays; 6.9806, 9.4, P. Dombrowski, Glastonbury, CT; 6.9917, 9.5, Bortle; 7.0424, 9.4, J. McKenna, Upper Montclair, NJ; 7.1486, 9.4, R. Royer, Lakewood, CA; 7.9833, 9.3, Gliba; 8.1028, 8.9, Collins; 9.1049, 9.0, Collins; 11.0924, 9.3, Gliba; 11.1326, 9.4, T. Burrows, Novato, CA; 12.0049, 9.0, Gliba; 12.0785, 9.2, A. Dill, Wichita, KS; 12.1215, 9.3, Burrows; 12.9896, 9.3, Dombrowski; 13.0132, 9.3, Bortle; 13.1201, 9.2, Burrows; 13.1618, 9.3:, Dillon; 13.9799, 8.8, Gliba; 13.9861, 8.6, Dombrowski; 14.0222, 9.0, Bortle; 14.0431, 8.9, McKenna; 14.2014, 8.8, Dillon; 14.87, 8.5, Zanotta; 15.09, 8.5, Zanotta; 15.1361, 9.2, Dillon. Accompanying are revised AAVSO 'b' and 'd' scale preliminary charts for N Cas 95. Please continue to monitor this star closely, and phone, fax, or email your observations to AAVSO Headquarters. It is interesting to note that the overall optical behavior of this nova has been and continues to be quite similar to that of HR Del, whose light curve we published in AAVSO Alert Notice 213. REQUEST TO MONITOR 2138+43 SS CYGNI The brightest northern hemisphere dwarf nova, SS Cyg, continues to be of interest to astronomers observing with various spacecraft. Throughout 1996, several satellites will be monitoring SS Cyg, namely IUE (during an anomalous, symmetrical outburst), XTE, and HST. We have been asked by astronomers at Space Telescope Science Institute, Lawrence Livermore National Laboratory, Goddard Space Flight Center, and the IUE stations in Vilspa, Spain, and in Germany to continue to monitor SS Cyg closely and to inform them of the start of outbursts from now until the end of the year. Please monitor SS Cyg and phone, fax, or email your observations to AAVSO Headquarters, particularly when you see the star brightening, i.e., growing brighter than magnitude 11.5, so we may inform the astronomers interested. REQUEST TO MONITOR 0207-63 WX HYDRI Astronomers at the Space Telescope Science Institute will be observing WX Hyi with HST in the second half of 1996. They have asked us to monitor WX Hyi closely all year long in order to have good coverage of its behavior. We ask our southern hemisphere observers please to monitor WX Hyi closely throughout the year, and report their observations to AAVSO Headquarters. REQUEST TO MONITOR 0324+43 GK PERSEI We have been asked to monitor GK Per closely (see AAVSO Alert Notice 211) and to inform astronomers in England as soon as it starts to brighten. GK Per, which shows minor outbursts every 2-1/2 to 3 years, is now overdue for a minor outburst. Thanks to all of you, it is being very closely monitored. The following recent observations indicate that it has been showing some activity, which may be a prelude to a minor outburst: Jan 15.1438 UT, 13.1, J. McKenna, Upper Montclair, NJ; 16.1618, 13.1, McKenna; 19.1417, 13.0, W. Dillon, Missouri City, TX; 21.0528, 13.2, J. Bortle, Stormville, NY; 26.0257, 13.1, Bortle; 29.1347, 13.2, McKenna; Feb 1.0278, 13.1, Bortle; 04.912, 13.0, G. Poyner, Birmingham, England; 7.0042, 13.1, Bortle; 11.1861, 12.9, T. Burrows, Novato, CA; 13.0188, 13.0, Bortle; 13.1097, 13.1, McKenna; 13.899, 13.1, Poyner; 14.0278, 13.0, Bortle; 15.1493, 12.9, Dillon. We once again remind observers to keep a close eye on GK Per and to call in your observations, particularly if you see it brighter than magnitude 12.7. The last outburst of this nova occurred in July 1992. FOLLOW-UP ON INTERNET SERVICE Following up on our warning of possible Internet service interruption (see AAVSO Alert Notice 217) due to the US federal budget impasse, we are happy to inform you that our network connection was NOT affected, and we continue to have very satisfactory connection to the Internet, and we thank NASA Astrophysics and NASA Science Internet for this. We invite our observers who have access to the Internet to visit our home page, where we have recently posted new light curves, including those of AM Her and N Cas 95, and some charts. We will continue to do this periodically. We welcome suggestions and recommendations from our observers and readers. CHARTS AVAILABLE ON AAVSO FTP SITE AND AAVSO HOME PAGE We have prepared electronic copies of the AAVSO charts of AM Her, V1159 Ori, and N Cas 95 mentioned in this Alert Notice. They are available from our FTP site: ftp.aavso.org (198.116.78.2), in /pub/alert218 They have also been placed on our home page: 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