COMMISSION 27 OF THE I.A.U.
               INFORMATION BULLETIN ON VARIABLE STARS
                            Number 1475

                                                      Konkoly Observatory
                                                      Budapest
                                                      1978 September 25


          CONCERNING VARIABLE STAR 7 IN M13

Variable star 7 in the globular cluster M13 = NGC 6205 was
suggested not to be a physical member of the cluster by Kadla
(1966, Iz. Pulkova Observ. 24, 93) based on her proper motion
study of M13. Non-membership seemed to be supported by the rather
short period of 0.2388d found for the star by Arp (1955, Astron.J.
60, 317). However, Ibanez and Osborn (1973, IBVS 769) found that
the associated period of 0.312393d apparently satisfied the available 
observational data somewhat better.
   New B and V photographic observations have been obtained
at the Michigan State University Observatory and the U.S. Naval
Observatory, Flagstaff Station. These new observations confirm
that the longer period is superior. Combining all the observational 
material for Variable 7, a best value for the period of
0.3126626d was found. There was no evidence for a period change
during the time covered by the observations.
   Furthermore, the new observations allow the B and V characteristics 
of the variable to be determined. The results are:

                             B       V      B-V

         Mean magnitude   15.14    14.86    0.28
         Total amplitude   0.31     0.26    0.05

These values make the star somewhat redder and fainter than found
by Demers (1971, Astron.J. 76, 445) and place it just redward of
the red edge of the horizontal branch in Sandage's (1970, 
Astrophys. J. 162, 841) HR diagram for M13. This strongly suggests 
cluster membership. In addition, Cudworth 1978, (152nd meeting of the
AAS in Madison, USA) has recently reported that a new astrometric
study yielded a proper motion for the variable consistent with
cluster membership. These results make it virtually certain that
Variable 7 is indeed a physical member of M13.
   The observational data and a complete discussion of this
work will be published elsewhere along with our results for the
other RR Lyrae stars of the cluster.


                             WALTER BISARD and WAYNE OSBORN

                             Physics Department
                             Central Michigan University
                             Mt. Pleasant, Michigan 48858,
                             U.S.A.