COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1336

                                  Konkoly Observatory
                                  Budapest
                                  1977 September 9




                   FO VIRGINIS



FO Vir is catalogued as RR ? in the Third Supplement to the
Third Edition of the General Catalogue of Variable Stars (1976)
and a period of 0.6 +- days is suggested. From 11 April to 2 July
1977, I have made 325 visual estimates of this variable and  I
have been able to determine 6 maxima, listed below:

Max. hel.          n    O-C
J.D.2443249.428   32   + .010
        250.558   34   - .004   
        259.418   24   - .006
        277.424   23   - .012
        285.455   15   + .014
        307.455   18   - .001

These times of maxima exclude the period value of about 0.6 and
suggest one close to 0.29 day; this is also confirmed by  the
daily light-curves. From the 6 maxima, an ephemeris can be calculated:

      Max = J.D. hel. 2443271.718 +0.28590 E        (1)
                          +- .013 +-.00017
and the O-C values of the third column are referred to it. The
second column lists the number of estimates to determine each
maximum. Notice that the phases predicted by (1) were actually
observed during the 20 nights of observation.
Using (1), a mean light-curve is obtained. A M-m value of 0.36
period can be derived and the shape of the curve suggests that
FO Vir is a RRc variable.



                                   E. PORETTI

                                      GEOS
                                   12 rue Bezout
                                   F-75014 Paris
Reference:

GEOS Circular NC 165, July 1977