COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 580

                                 Konkoly Observatory
                                 Budapest
                                 1971 September 15


     HDE 302013 - A NEW SHORT-PERIOD VARIABLE STAR


          
HDE 302013 is at 11h49.8m, -55d38' (1971), about 8' S and
5' E of the open cluster NGC 3960;, a finding chart is given
            in Figure 1. Variability was detected during
            a programme of photoelectric UBV observations
            of the cluster. Magnitudes range from V=10.24,
            B-V=0.20, U-B=0.22 at maximum to V=10.64,
            B-V= 0.34, U-B=0.21 at minimum. These colours
[FIGURE 1]   
            are compatible with the HDE spectral type of
            A5, which is confirmed on a spectrogram by
            M.S. Bessell, the analysis of which will be
            published elsewhere. It therefore appears
            very unlikely that the star could be a member
            of NGC 3960, Which has a reddening of E(B-V)~
            0.35 and brightest red giants at V~11.6.


                     [FIGURE 2]

     A light curve is shown in Figure 2, derived only
from observations made on one night (filled circles). The
star seems to be a short-period cepheid (RRc) of the halo
population. The variability is apparently regular; scattered
observations made between March and August 1971 can all be
fitted to the above light curve with a uniquely determined
period of 0.22135d, the maximum of Figure 2 occurring at
HJD = 2441107.028. The isolated observations are shown as
crosses in Figure 2.
      The nearly sinusoidal shape of the light curve, and
the suggestion of a bump shortly before maximum, favour the
interpretation that the star is a short-period halo cepheid
(RRc) with the very short period of 5.3124 hours. Further
observations will be required next season to confirm this.
We are indebted to M.S. Bessell and R.S. Stobie for valuable
discussion, and to K.C. Freeman and B.A. Peterson for some of
the observations used to determine the period.


                  R.S. CANNON and O.J. EGGEN
           Mount Stromlo and Siding Spring Observatories
               Research School of Physical Sciences
                The Australian National University