COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                    Number 3128


                                     Konkoly Observatory
                                     Budapest
                                     8 January 1988

                                     HU ISSN 0374-0676





         COORDINATED MULTIWAVELENGTH OBSERVATIONS OF YY Gem


  From 4-6 March 1988 a coordinated programme of observations of
the eclipsing binary flare star, YY Geminorum, is planned
involving IUE, GINGA (X-rays) and various ground-based
facilities. The principal objectives of this programme are (1)
to provide data on the surface structure of the two components of
YY Gem by the techniques of rotational modulation and eclipse
imaging, and (2), to observe flares over as many different
wavelength regions as possible. This project presently involves
the following institutes: Armagh Observatory, the Institute of
Astronomy at the University of Catania, the Joint Institute for
Laboratory Astrophysics of the University of Colorado, the
Rutherford-Appleton Laboratory, Oxfordshire, the Laboratoire de
Physique Stellaire et Planetaire du CNRS and the Institute for
Astronomy of the University of Hawaii.

  The purpose of this circular is to solicit observations from
ground-based telescopes around the world during the period 19:00
UT 4 March to 19:00 UT 6 March 1988, with particular emphasis on
the eclipses at the following times:

           primary               secondary

                               4 March UT=15:06
         5 March UT=00:52      5 March UT=10:38
         5 March UT=20:29      6 March UT=06:10
         6 March UT=15:56

   Optical eclipses last approximately 2.15 hours.

   YY Gem is a ninth magnitude companion of the bright star Castor
from which it is separated by approximately one minute of arc.
In order of preference, suggested comparison stars are the
following: SAO 60181, SAO 60182 and SAO 61217.

  We welcome the participation of any observer who can
contribute either photometric or spectroscopic observations.
Interested observers are requested to contact the undersigned and
to notify us of their telephone and telex numbers and/or BITNET.





                        C.J. BUTLER

                        Armagh Observatory,
                        College Hill,
                        ARMAGH,
                        BT61 9DG,
                        N. Ireland.



            Tel. (94) 861 522928 Telex 797937 ARMOBS G
            BITNET address CJB @ UK.AC.RL.STAR