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 204 (March 22, 1995) A VERY SUCCESSFUL ASTRO-2 MISSION COMPLETED Space shuttle Endeavour landed on March 18, 1995, after a very successful ASTRO-2 Mission. This is a brief report on the mission for the observations of variable stars, particularly cataclysmic variables (CVs). Thanks to your enthusiastic response and dedicated monitoring of variable stars in the observing program of the ASTRO-2 mission, we provided continuous updates, quite often three times in 24 hours, to the scientists at Marshall Space Flight Center on the behavior of these stars. I want to share with you some of the e-mails I received from the ASTRO-2 Science Team during the mission, updating us on its status: March 2 - " As I write this, we are 1hr 30 minutes into the flight and all looks well..." March 4 - "... We got our first observations of CVs this morning. VW Hyi was still in quiescence...we see the WD {white dwarf}... we also have a short spectrum of YZ Cnc {at minimum}... Overall things are going very well... continued thanks..." March 8 - "We obtained excellent observations of SS Cyg and U Gem this morning. Both are quite different from what we observed with Astro-1, presumably due to the fact that they are much further along from outburst than then. ...The reports you have been sending have been extremely useful.. Continued thanks" March 9 - "Our observation of WX Hyi last night {fading from maximum} was quite interesting, with very high energy lines present. It is important to get good continued magnitudes for it -- as we wait for VW Hyi. Thanks..." March 9 - " We have just begun the first two LONG (3000 seconds) AM Her exposures with HUT {Hopkins Ultraviolet Telescope} on the Astro-2 Mission! The data are coming in in real time, and they look great!!... Thanks again for all your work..." March 10 - "Our observations today of AM Her {at bright state} and EM Cyg {at maximum} were quite spectacular. We observe Z Cam and WX Hyi tomorrow..." March 11 - ".. our coordinated observations with ASCA {x-ray satellite) on Z Cam were successful. While ASCA was recording 0.2 counts/s, HUT was recording 2500 counts/s..." March 11 - "We should have observed EF Eri {at minimum state} this morning and WX Hyi once again this evening. We are awaiting for EM Cyg to start down before observing it again -- and for VW Hyi (or U Gem) to go off. All is well here..." March 13 - "Can you give me an indication of what you think EM Cyg is likely to do - i.e. is it likely to start going down soon. We observed it for the second time last night. The HUT spectrum looked similar to the one we observed 3 days ago {at maximum}. Thanks..." March 14 - "Thanks for the information. I hope it goes down {it did!}. It looks like the end of science operations for Astro will be Thursday night and the shuttle will return to earth on Friday afternoon {it returned one day later due to weather}... Thanks again..." March 15 - "Thank you for the information about EM Cyg {started to fade}. We are going to observe it tomorrow, which will be the last CV observation for Astro-2. Shutdown for the experiment is tomorrow night. Please communicate to everyone how valuable their help has been for us... Here is a complete list of the CVs we observed, in no particular order: "SS Cyg, U Gem, VW Hyi, EF Eri, AM Her, EM Cyg, WX Hyi, Z Cam, EX Hya, and YZ Cnc. "It's pretty impressive... Best regards and thanks again..." The above sampling of e-mails speaks for itself of your significant contributions to this mission. Besides the cataclysmic variables, variable star targets ASTRO-2 monitored included symbiotic stars and a few of the recent novae. Again, your observations helped in the satellite scheduling of these objects - as William Blair, a mission scientist, said, "That's crucial information for us. It's driving the way we're planning observations, what we want to do with these targets." For your interest, accompanying this Alert Notice are AAVSO light curves of 12 of the ASTRO-2 target cataclysmic variables, including observations reported to the AAVSO by you through March 19-20, two days after the end of the mission. Your efforts were VERY MUCH appreciated by the whole ASTRO-2 Science Team and by the NASA ASTRO-2 Program Scientist, so much so that NASA arranged a phone interview for me with an Associated Press editor to give information on the contribution of amateur astronomers to this mission. A very nice article was prepared and released by the Associated Press which was published on March 9 in different parts of the country; a copy of the article as it appeared in the Boston Globe accompanies this Alert Notice. After the publication of the article, both the public affairs people at Marshall Space Flight Center and we at AAVSO were contacted by several reporters who wanted to interview the amateur astronomer(s) in their community who were contributing to ASTRO-2. Several observers have already been contacted by the press. If an article about you has appeared in your local newspaper, we would very much appreciate receiving a copy for the AAVSO archives. In addition, NASA arranged for a reporter-and-videographer team to visit the AAVSO to film a story on how we at the AAVSO were coordinating this project. Also, our member Bill Dillon, who lives near a NASA Center, was interviewed as to how he was doing his observing for the ASTRO-2 mission. These interviews were combined into a program, which was aired on NASA-Select television several times, starting on Sunday, March 11. Later the NASA ASTRO-2 Program Scientist wrote: March 13 - "I was delighted by the Mission Update story Sara Moquin and Mike Arrington put together on AAVSO. It is at least a small testimony to the high regard in which this particular mission, and NASA Astrophysics, in general holds the contributions of AAVSO and its dedicated membership..." All of this acknowledgment is truly a testimony to the important role that you, our observers, played in the success of the observations of variables for this Mission. If you have a photograph of yourself with your telescope and/or observatory please send us a print for our records. We would like to make a collage of these photographs for this and future missions and observing programs. Please continue to monitor the following CVs that were observed with the ASTRO-2 so that we can provide a complete set of data for before, during, and after the mission to the Science Team for the correlation of the satellite data: 0139+37 AR And 0804+28 YZ Cnc 0640-16 HL CMa 0207-63 WX Hyi 0814+73 Z Cam 0829+53 SW UMa 0219+27 RW Tri 1247-28 EX Hya 1004-69 OY Car 0309-22 EF Eri 1813+49 AM Her 1325-54 BV Cen 0409-71 VW Hyi 1934+30 EM Cyg SUPEROUTBURST OF 1051+50 CY URSAE MAJORIS The dwarf nova-type cataclysmic variable (SU UMa subclass) is having a superoutburst, as indicated by the following observations: Mar 13.874, <13.2, G. Poyner, Birmingham, England; 18.044, <13.2, P. Schmeer, Bischmisheim, Germany; 18.974, <13.2, Poyner; 19.892, 12.3, Schmeer; 19.897, 12.4, Poyner; 20.025, 12.3, Schmeer; 20.814, 12.2, Schmeer; 20.948, 12.1, Schmeer; 21.136, 13.3, M. Adams, Fort Davis, TX; 21.85, 12.7, L. Jensen, Farum, Denmark; 21.969, 12.3, Schmeer; 22.845, 12.4, Schmeer. 3—3  Š The last superoutburst of CY UMa was in the end of March to the beginning of April 1993, when it reached magnitude 11.9 at maximum. Please use the accompanying AAVSO "e" scale chart in making your observations. We note that the sequence by S. Fujino, Japan, on a finder chart provided to us by Patrick Schmeer, Germany, is significantly brighter than that of AAVSO's. The AAVSO photovisual sequence was obtained by Charles Scovil, extrapolating from the photoelectric magnitudes of the Guide Star Photoelectric Catalog (Lasker et al. 1988, ApJ. Suppl., 68, 1), which should not be confused with the Guide Star Catalog on CD-ROM. Below are the magnitudes from the finder chart by the AAVSO and by Fujino: AAVSO magnitude Fujino magnitude Compass direction 115 --- N --- 137 N 147 140 NE 148 139 SE 135 129 SE --- 132 SE 123 --- SE 156 146 SW 140 136 SW 108 --- SW --- 116 SW 132 124 W --- 150 NW 144 137 NW We welcome comments from observers on both sequences. We are very concerned about the inhomogeneity of the magnitude sequences used among observers around the world. It becomes extremely difficult to compile observations from observers who do not use the same sequence. We try hard to have a sequence that is satisfactory, however, we do not claim that AAVSO sequences are the best. We are in the process of having a rigorous evaluation of our Preliminary Chart sequences. Again, we welcome comments from our observers, who are the ultimate judges on the quality of the sequences. OUTBURST OF 0203+56A UV PERSEI The dwarf nova-type cataclysmic variable (SU UMa subclass) UV Per has undergone and is beginning to fade from a short outburst, as indicated by the following observations: Mar 7.863, <14.9, G. Poyner, Birmingham, England; 8.808, <14.9, Poyner; 10.080, <14.1, T. Vanmunster, Landen Belgium; 11.032, 18.1 CCDV, R. Zissell, S. Hadley, MA; 11.133, <14.1, Vanmunster; 12.819, <14.9, Poyner; 13.851, <14.3, Poyner; 18.808, <15.2, Poyner; 19.393, <15.6, Poyner; 20.833, <13.5, P. Schmeer, Bischmisheim, Germany (via G. Poyner); 20.911, 13.9, B. Worraker, Didcot, England (via G. Poyner); 21.104, 12.6, M. Adams, Fort Davis, TX; 21.78, 12.3, L. Jensen, Farum, Denmark; 21.80, 12.5, M. Verdenet, Bourbon-Lancy, France; 21.801, 12.8, L. Szentasko, Budapest, Hungary; 21.809, 12.9, J. Pietz, Erftstadts, Germany; 21.816, 12.3, Schmeer; 21.83, 12.8, Verdenet; 22.000, 12.7, J. McKenna, Upper Montclair, NJ; 22.840, 13.5, Schmeer. The last outburst of UV Per, a superoutburst, occurred in late May - early June 1994, when it reached magnitude 11.8 at maximum (please see AAVSO Alert Notice 186). Please use the AAVSO "f" scale chart that was distributed with AAVSO Alert Notice 186 to monitor UV Per. We again note that the sequence on this chart was revised in 1981, and that observers should NOT use the pre-1981 UV Per charts. Also, when reporting your observations to AAVSO Headquarters, please indicate which chart (including date of issue) and which comparison stars you are using. REMINDER -- MONITORING 0749+22 U GEMINORUM U Gem continues to be at minimum since its outburst in August-September 1994. This is the longest minimum with no observing gaps since 1984. Several astronomers with observing programs using EUVE and HST are awaiting the next outburst. Please continue to monitor U Gem closely and inform us as soon as you observe it brightening, i.e., magnitude 13.5 and brighter. U Gem has fairly deep (0.5 magnitude) eclipses of the "hot spot" on the accretion disk by the cool companion. Dr. B. Paczynski of Princeton University, who strongly recommends that visual and particularly CCD observers monitor the eclipses, recently wrote, "The eclipses last only about 10 minutes. Their width varies by a factor of almost 2 with time: they are widest right after the eruption, and gradually narrow down with time, being the narrowest just before the eruption. This change is believed to be caused by the change in the geometrical size of the accretion disk ... It would be very interesting to find out what is the eclipse now, over 200 days since the last eruption." Magnitude estimates of the eclipses should be made every minute and recorded to four places of the decimal of the JD. The eclipses have the following elements (J. Smak 1993, Acta Atronomica, 43, 121): HJD Primary Minimum = HJD 2437638.82627 + 0.1769061898 * E, (+/- 8) (+/- 30) where E is the cycle number. In addition to the eclipses, U Gem has a "hump," a photometric feature with an amplitude of 0.7 magnitude that lasts half of the orbital period and peaks at phase 0.85, where phase 0.00 is the middle of the eclipse. Dr. Paczynski also suggests that observers monitor these "humps," particularly while U Gem begins its rise. The humps disappear when the system brightens to magnitude 12 and re-appear again after the outburst when U Gem becomes fainter than magnitude 12. The hump is believed to be due to the "hot spot" created by the stream of material from the cool companion colliding with the outer edge of the accretion disk. Dr. Paczynski writes further, "...little is known about the stability of this 'hump,' yet it provides a direct measure of the amount of energy released in the stream-disk collision. It is not known is it constant between the eruptions, is it constant from year to year, and in particular, how does it look ... now, when U Gem has not erupted for over 200 days." CORRECTION TO AAVSO ALERT NOTICE 196 - 2110+13 EF PEGASI The location of the close companion to EF Peg should read 5.34 arcseconds away at position angle 112 degrees (Howell et al. 1993, Publ. Astron. Soc. Pacific, 105, 579). We thank Patrick Schmeer for bringing this correction to our attention. Observers are welcome to use our charge-free number (800-642-3883) to report observations. The answering machine is on nights and weekends for your convenience. We also encourage observers to send observations by fax at 617-354-0665 or by e-mail through the Internet at aavso@cfa.harvard.edu. Again, on behalf of the ASTRO-2 Science Team and all of us at Headquarters, my sincerest thanks to you for your dedicated efforts and valuable observations. Good Observing! Janet A.Mattei Director