COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       Number 910

                                       Konkoly Observatory
                                       Budapest
                                       1974 July 19


  A SUSPECTED PERIOD INCREASE IN THE ECLIPSING BINARY RW Per

   The purpose of this note is to draw attention to a possible
period change that has occurred in the eclipsing binary RW Per.
Spectroscopic observations of RW Per were made at the Dominion 
Astrophysical Observatory on March 19, 1974 with the hope of observing
circumstellar emission lines during totality. According to the 
ephemeris of Woodward (Harvard Bull. 917, 7, 1943), as listed by 
Kordylewski (Rocznik Astronomiczny Observatorium Krakowskiego, 1973),
mid-eclipse was predicted to occur at 04:12 UT March 19. Two 
spectrograms were obtained:

Plate Number         Time of mid-exposure (UT)   Exposure Time (min.)
   76046                      04:10                      63m
   76047                      05:39                     113m

On the first plate there was an A-type spectrum, with no evidence
of any lines of the secondary, while on the second plate the 
prominent hydrogen lines were weaker, and metallic lines from the 
secondary component had begun to show up. From this spectroscopic 
evidence, it appears that the eclipse was 3 to 5 hours later than 
predicted.
   Hall (Mass Loss From Stars, pp. 171-83, 1969) has listed all available 
times of primary minimum for RW Per. The corresponding (O-C)
diagram, based on Woodward's ephemeris, reveals that the four most
recent times of minima deviate systematically from the course of the
earlier ones. These four times are listed below and are plotted in
the following (O-C) diagram. The time of minimum estimated 
spectroscopically has also been included as a vertical bar in the diagram
and it is apparent that it confirms the trend in the residuals.
The following ephemeris is based on a least-squares fit to the
four photometric times of minima:

   T_{min} = JD 2429217.274 + 13d.19894.E

Certainly this new ephemeris is only a provisional one, and times of
minima are needed in the future in order to confirm it. If it proves
to be correct, then it can be concluded that a period increase off
magnitude Delta-P/P ~ 4 x 10^(-5) occurred at E ~ + 700.

          Recent times of Minima for RW Per

Heliocentric JD   Epoch   (O-C)                Reference
2400000.+                  days
38456.53          +700   +0.025     Kordylewski (IBVS No.46,1964)
39063.684         +746   +0.050     Hall (Mass Loss From Stars,171,1969)
39076.883         +747   +0.051     Hall (Mass Loss From Stars,171,1969)
39802.822         +802   +0.075     Hall (Mass Loss From Stars,171,1969)


                         [FIGURE 1]


University of Victoria                  BARROW W. BALDWIN
P.O. Box 1700, Victoria,
B.C., Canada.