COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2677


                                   Konkoly Observatory
                                   Budapest
                                   1 March 1985

                                   HU ISSN 0374 - 0676


        AK Her - NEW V LIGHT CURVE AND PERIOD CHANGE

 Photoelectric observations of the W UMa - type eclipsing binary AK Herculis
were carried out on three nights of May 16/17, May 17/18, June 29/30, 1983.
The observations were made at Cracow Astronomical Observatory with the 50 cm
reflector equipped with EMI 9789 QB photomultiplier. The Schott filter GG-11
in V region was used. The comparison star was BD+16d3123 and BD+16d3124 served
as a check star. The comparison star was the same as used most often in previous
investigations (Binnendijk, 1961; Woodward and Wilson, 1977; Bookmyer and
Kaitchuck, 1979). Two hundred observations in V light in the sense of variable
minus comparison are shown in Figure 1. A slight phase shift of secondaries to
value 0.502 can be seen.

                               [FIGURE 1]

   Times of minima obtained from these data with the Kwee and Van Woerden
   (1956) method are given in Table I.

             Table I
JD Hel        O-C days   Min type
--------------------------------
2440000+
5471.38030   +0.0139       I
      +-18
5472.43500   +0.0147       II
      +-31
5515.43033   +0.0148       II
      +-32
--------------------------------

The O-C values computed from the ephemeris published by Barker and Herczeg
(1979)

           J.D.Hel.Min.I = 242 3573.7060 + 0.42152227d E

are plotted versus epoch in Figure 2. All points following J.D. 2433000 refer
to photoelectric data.

                          [FIGURE 2]

As the (O-C) diagram illustrates, a satisfactory light-time representation is
possible as was suggested in the past (Herczeg and Schmidt, 1959; Rafert, 1982).
A new period obtained for these data by a least squares fitting is equal to
65.95 years with an amplitude 0.0147d. The computed residuals from this sinusoid
are shown in the lower part of Figure 2. The observations of AK Her covers
only 80 years, so the problem of multiplicity of system is still open (Woodward
and Wilson, 1977; Panchatsaram and Abhyankar, 1982).
 From 29 photoelectric minima observed since 1976 we can find new linear
elements :

     J.D. Hel.Min. I = 244 2665.3091 + 0.42152202d*E
                                +-93         +-19
The relative period change in the manner of sudden period changes is
 DeltaP/P ~ - 6.10^-7.
 The author would like to thank Dr. M. Winiarski for help during his stay
in Cracow and the Astronomical Observatory for granting telescope time.





                             ZBIGNIEW GLOWNIA

                             Laboratory of Astronomy
                             Silesian University
                             ul. Uniwersytecka 4
                             40 007 Katowice
                             Poland





References:

Barker, L.A., Herczeg, T.J., 1979, Pub. A.S.P. 91, 247 [BIBCODE 1979PASP...91..247B ]
Binnendijk, L., 1961, A.J. 66, 27 [BIBCODE 1961AJ.....66...27B ]
Bookmyer, B.B., Kaitchuck, R.H., 1979, Pub. A.S.P. 91, 234 [BIBCODE 1979PASP...91..234B ]
Herczeg, T.J., Schmidt, H., 1959, Zs. f. Ap. 47, 196 [BIBCODE 1959ZA.....47..106S ]
Kwee, K.K., Van Woerden, H., 1956, B.A.N. 12, 327 [BIBCODE 1956BAN....12..327K ]
Pantschatsaram, T., Abhyankar, K.D., in Binary and Multiple Stars as Tracers
     of Stellar Evolution eds. Z. Kopal and J. Rahe, Dordrecht, 1982 [BIBCODE 1982ASSL...98...47P ]
Rafert, J.B., 1982, Pub. A.S.P. 94, 485 [BIBCODE 1982PASP...94..485R ]
Woodward, E.J., Wilson, R.E., 1977, Ap. and Space Sci. 52, 387 [BIBCODE 1977Ap&SS..52..387W ]