COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1152

                               Konkoly Observatory
                               Budapest
                               1976 July 14


          ON THE PERIODIC VARIATION IN PERIOD
               OF SIX RR LYRAE TYPE STARS


    We have found periodic fluctuations of the O-C residuals
in the following RR Lyrae type stars:
             RV CrB    -Pi~= 18400d
             RR Gem    -Pi~= 25600d
    The change of the O-C residuals for three other stars
(RW Dra, SZ Hya, SV Eri) also indicates a possible periodicity
in period variation.
    For RV CrB and RR Gem preliminary calculations have been
made assuming that these RR Lyrae type stars are components of
binary systems. However, this attempt of interpretation cannot
be considered satisfactory as the mass sum of the components of
suspected binary systems amounts to as high as: m_1+m_2 = 10^2-10^3
of the Sun's mass.
    Similar variations in period might be caused by dynamic
factors.
    In figures below the graphs of the O-C fluctuations
through the following time intervals are given:
          RV CrB - J.D. 2417800-2442800
          RR Gem - J.D. 2415000-2442800
          RW Dra - J.D. 2417400-2442700
          SZ Hya - J.D. 2415000-2442800
          SV Eri - J.D. 2414000-2441700


                            B.N. FIRMANYUK

                      Odessa Astronomical Observatory

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