COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 949

                                      Konkoly Observatory
                                      Budapest
                                      1974 December 6


            REQUEST TO FLARE STAR OBSERVERS

    We are planning an extensive series of X-ray observations of the flare star UV-Ceti
(1950 r.a. = 01h36m25s, 1950 dec = -18deg12.7') with the Astronomical Netherlands Satellite
(ANS) during 3-8 January 1975. The Smithsonian X-ray experiment on ANS will observe in
the 1-30keV energy range with 1 sec time resolution and spectrum recording every 4 seconds.
Flares could be detected to at least the limit ~ 5 x 10^-10 erg/cm^2sec in the 1.5keV-7keV band.
In addition, the soft X-ray (0.25keV-8keV) experiment on ANS will be observing with comparable 
sensitivity and time resolution. On 5 and 6 January it will be possible for the third ANS
experiment, a uv telescope (1500-3000 A), to also observe the star. The satellite can maintain 
pointing (within an arc minute) on the star for about 15 minutes during each 98-minute
orbit.

    We urgently request all possible optical observers to search for flares during this
period. We hope observers will record data with high time resolution for as long as possible
while the star is visible after local sunset. Due to the satellite orbit, especially long observations 
are possible over Asia and Australia. Observers can obtain a list of approximate
ANS observing times by 20 December upon notifying either Dr. J. Grindlay at the Center for
Astrophysics or Dr. J. Heise, Laboratory for Space Research, Beneluxlaan 21, Utrecht,
Netherlands (telex no. 47224).

    During a similar observing program on YZ-CMI in 1974 October, it is very likely that
we detected an X-ray flare. Unfortunately there was no coincident optical or radio observation
at that particular time. We hope it will be possible for many observers to monitor UV-Ceti
and communicate times of any flares to us.





                                             JONATHAN. E. GRINDLAY
                                             Center for Astrophysics
                                             Harvard/Smithsonian Observatories
                                             60 Garden Street
                                             Cambridge, MA 02138
                                             Telex no. 921428