COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       Number 972

                                     Konkoly Observatory
                                     Budapest
                                     1975 March 11


           PERIOD INCREASE IN RW PERSEI CONFIRMED

    The purpose of this note is to present a new time of primary
minimum for the Algol-type eclipsing binary RW Persei which confirms
the period increase suspected by Baldwin (1974).
    The time was derived from differential UBV photoelectric 
observations obtained at Dyer Observatory on four different nights in 1970.
One of these nights was on the falling branch, the other three on the
rising branch. There was relatively little overlap, and this occurred
only about 0m.3 down from maximum light; thus the derived time is in
principle vulnerable to any asymmetry which might have been present
in the light curve. With the tracing paper method the time of minimum
was determined to be JD(hel.) = 2,440,898.3330 +- 0d.0005. Here the 
error is that indicated by examining the three colors separately, but
the real uncertainty could be somewhat more.

    The O-C residual based on the ephemeris
                   JD(hel.) = 2,429,217.587+13d.198454 E
is +0d.114 at E = + 885. This value fits very nicely in the O-C 
diagram of Baldwin and thus confirms the suspected period increase, which
is supposed to have occurred around 1960. Baldwin's suggested provisional 
new ephemeris
                     JD(hel.) = 2,429,217.274+13d.19894 E
yields an O-C residual of only -0d.003 at E = +885, which is not large
enough to call for a refinement of his period at this time.


                                     DOUGLAS S. HALL
                                     TILMAN STUHLINGER
                                     Dyer Observatory
                                     Vanderbilt University
                                     Nashville, Tennessee 37235
                                     U.S.A.
References:
Baldwin, B.W. 1974, I.B.V.S. No. 910