THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS 25 Birch Street, Cambridge, MA 02138 USA Tel. 617-354-0484 Fax 617-354-0665 http://www.aavso.org * * * AAVSO NEWS FLASH * * * Subject: 1803+05 V426 OPH CHANDRA OBSERVATIONS No. 968 XMM OBSERVATIONS - T LEO and AB DRA May 22, 2002 0006-12 WW CET REMINDER - RXTE OBSERVATIONS 0939+52 ER UMA 1841+37 AY LYR 1017-49 V383 VEL 1953+77 AB DRA ---------------------------------------------------------------------------- NOTE: We would like to inform our observers that the AAVSO Validation File was updated May 20. The updated file and lists of changes made have been posted on our website. (http://www.aavso.org/validation.stm) Please be sure to update your copy of the AAVSO Validation File. ---------------------------------------------------------------------------- 1803+05 V426 OPH REQUEST TO MONITOR FOR CHANDRA OBSERVATIONS Our colleagues, astronomers at the University of Washington, will be observing V426 Oph with the Chandra X-Ray satellite on May 30, starting at 22:00 UT, with a duration of 45 ksec (12.5 hr). The following description of the project was provided by our colleagues: The primary goal of the Chandra observations of V426 Oph is to obtain a high resolution X-ray spectrum of this dwarf nova. This will help us to determine temperature and density information for the inner accretion disk and also help us infer the path followed by accreting material in the transition zone between the inner disk and the white dwarf. We can also construct X-ray light curve(s) by looking at the summed photon detections as a function of time during the observation. As far as the goal of the ground-based observations, on one level it will be useful for us just to know the mean brightness level of the system to get an idea of the accretion state, so a few observations per night for a few nights on either side of the Chandra observation would be useful. On another level, CCD time-series observations at high time resolution will be useful for comparing rapid variability in the optical to any such behavior we might observe in the X-ray. We ask that both visual and CCD observers keep a close eye on V426 Oph leading up to and following this observing run, but particularly during the Chandra observations. CCD observers are particularly encouraged to observe with a V filter as frequently as possible (at least every three minutes) during the observing run. ---------------------------------------------------------------------------- XMM OBSERVATIONS - T LEO and AB DRA As mentioned in News Flash No. 950 and 962, our colleagues at the University of California in Santa Barbara have been/will be observing a number dwarf novae using the X-ray Multi-Mirror (XMM) satellite. They have asked us for help in monitoring the variables optically. Two new variables have recently been added to their list. The dates of observation are listed below: Object Start of Observation (UTC) Duration ====== ========================== ======== T Leo JUN 01 08:40 7.2 hrs AB Dra JUN 02 20:40 3.5 hrs Please keep a close eye on these variables for as long as you can on the dates of their observation. In addition, please monitor these objects closely before (starting now) and after the XMM observations so that the visual light curve can be correlated with the X-ray data. CCD observers are strongly encouraged to monitor the above targets with V filters. ---------------------------------------------------------------------------- 0006-12 WW CET - REMINDER TO MONITOR FOR RXTE OBSERVATIONS As mentioned in AAVSO Alert Notice 295, astronomer Dr. Darren Baskill of Leicester University, Leicester, UK, will be observing the dwarf nova WW Ceti with the Rossi X-ray Timing Explorer (RXTE) from May 10 through August 9, 2002 for a duration of 3,000 seconds each day. He has requested the assistance of AAVSO observers to monitor WW Cet simultaneously with his X-ray campaign so that the visual and X-ray data may be correlated. For a more detailed description of the project, including information on recommended frequency of observation and RXTE observing timetables, please see both AAVSO Alert Notice 295 and Dr. Baskill's web page dedicated to this observing run.(http://www.star.le.ac.uk/~dbl/xtewwcet.html) ---------------------------------------------------------------------------- 0939+52 ER URSAE MAJORIS The dwarf nova type (SU UMA subclass) cataclysmic variable ER UMA appears to be in outburst, as indicated by the following observations: AAVSO Observer AAVSO Observer UT Mag. Initials UT Mag. Initials MAY 18.9259 <14.0 MGH MAY 21.0957 12.9 TSC MAY 20.8700 14.76 CCD DRG ---------------------------------------------------------------------------- 1017-49 V383 VELORUM The dwarf nova type cataclysmic variable V383 VEL appears to be in outburst, as indicated by the following observations: AAVSO Observer AAVSO Observer UT Mag. Initials UT Mag. Initials MAY 19.5550 <15.0 PEX MAY 21.3829 12.7 SRX ---------------------------------------------------------------------------- 1841+37 AY LYRAE The dwarf nova type (SU UMA subclass) cataclysmic variable AY LYR appears to be in outburst, as indicated by the following observations: AAVSO Observer AAVSO Observer UT Mag. Initials UT Mag. Initials MAY 21.9306 <15.6 RMQ MAY 22.2437 14.4 SXN MAY 22.1916 14.0 TDB ---------------------------------------------------------------------------- 1953+77 AB DRACONIS The dwarf nova type (Z CAM subclass) cataclysmic variable AB DRA appears to be in outburst, as indicated by the following observations: AAVSO Observer AAVSO Observer UT Mag. Initials UT Mag. Initials MAY 18.0249 14.5 RMQ MAY 21.9416 12.7 RMQ ---------------------------------------------------------------------------- We thank the following contributors for the data that they have provided for this News Flash: DRG - R. DIETHELM, SWITZERLAND SRX - R. STUBBINGS, AUSTRALIA MGH - H. MCGEE, ENGLAND SXN - M. SIMONSEN, USA PEX - A. PEARCE, AUSTRALIA TDB - D. TAYLOR, CANADA RMQ - M. RESZELSKI, POLAND TSC - S. TRACY, USA Please monitor these and other variable stars closely and phone-in, fax, or e-mail your observations to the AAVSO. Good observing! Janet A. Mattei, Director Rebecca Pellock, Technical Assistant ____________________________________________________________________________ Symbols may include: < = fainter than magnitude given (variable not seen) : = uncertain CCDV = Charge-coupled device with (V) filter If you would like to contribute to AAVSO NEWS FLASH, please send observations of unusual variable star activity to: observations@aavso.org Those who wish to subscribe (free of charge) or unsubscribe to NEWS FLASH may do so by visiting the following web page: http://www.aavso.org If you would like data from the AAVSO International Database for research purposes, please send your request to: Janet Mattei, AAVSO Director, at aavso@aavso.org An archive of past issues of the News Flash is available at the following web page: http://www.aavso.org/newsflash/ We look forward to including your observations in future editions of AAVSO NEWS FLASH! ____________________________________________________________________________