COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                          NUMBER 75


                                         Konkoly Observatory
                                         Budapest
                                         20 November 1964

                ON THE NATURE OF VARIABLE STARS
                      IN M 67 AND NGC 188

      The discovery of ultra-shortperiod variables in old
galactic clusters M 67 (N. Kurockin, 1960a, 1960b) and NGC 188
(C. Hoffmeister, 1964a, 1964b) is extremely interesting. The presence
of these stars in old galactic clusters is perhaps typical. According
to the discoverers these variables are RR Lyrae-type or RR Lyrae-
similar stars.
      Recently photometrical investigations of the stars in M 67
(O. J. Eggen, A. R. Sandage, 1964) and NGC 188 (A. R. Sandage, 1962)
have been published. The colour excesses E (B-V) in M 67 and NGC
188 are very small (0m.05 and 0m.06 respectively).
      The variable S 8280 (C. Hoffmeister, 1964b, P = 0d.15 is
identical with the star No 114 (Ring II) in NGC 188. It has (B-V)_0=+0m.87
and M_v=+4m.8.
      The variable SVS 1284 (N. Kurockin, 1960b, P = 0d.13) is
identical with the star Vanderlinden 687 (H L. Vanderlinden, 1945) of
spectral class GO (Trumpler) and M_v=+3m.2. This variable is also
identical with the star III-33 on Eggen and Sandage's map.
      It is also significant that the variable SVS 1277 (N. Kurockin
1960a, P=0d.15) near M 67 has M_v=+3m.6 and spectrum K0 (G. Herbig,
1961).
      All these variables are situated on the upper boundary of the
main sequence and there is no similarity of their position in the HRD
to that of ordinary RR Lyrae stars or dwarf RR Lyrae stars. Very
probably all these variables belong to the W Ursae Majoris type and it
is necessary to double their periods.

      The presence of W UMa variables in old galactic clusters is
very surprising. The search for these variables in old galactic and
globular clusters is extremely desirable.

     We should like to thank Prof. Dr. C. Hoffmeister for 
identification map of the variable stars in NGC 188.


     REFERENCES

O. J. Eggen, A. G. Sandage, ApJ 140, 130, 1964. [BIBCODE 1964ApJ...140..130E ]
G. Herbig, private communication, 1961.
C. Hoffmeister, MVS Bd. 2, Heft 3, 1964a.
C. Hoffmeister, Inf. Bull. V. S. 67, 1964b. [IBVS 67]
N. Kurockin, Astr. Circ. USSR, 210, 1960a. [BIBCODE 1960ATsir.210...25K ]
N. Kurockin, Astr. Circ. USSR, 212, 1960b. [BIBCODE 1960ATsir.212....9K ]
A. R. Sandage, ApJ 135, 333, 1962 [BIBCODE 1962ApJ...135..333S ]
H. L. Vanderlinden, Medd. Univ. Gent, No. 10, 1945.

Sternberg State Astronomical Institute
Moscow, 11 Nov. 1964


                              Y. N. EFREMOV
                              P. N. KHOLOPOV
                              B. V. KUKARKIN
                              A. S. SHAROV