COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 753

                                   Konkoly Observatory
                                   Budapest
                                   1973 January 5




  THE VARIATIONS OF THE  LIGHT CURVE OF HZ HERCULIS IN THE
                       35-DAY CYCLE


      The features of the light curve of HZ Her at different phases
of the 35d variation in X-ray emission were investigated. 318 plates
(1907-1972) of the Sternberg Institute and photoelectric observations 
of Lyutiy et al.(1972) were used. According to H. Gursky (1972)
X-ray maxima were observed on JD 2441330.2  and JD 2441400. It
was found that the bright optical maxima were usually observed at.
the middle and at the beginning of the 35d cycle. Using the X-ray
observations and the brightest optical maxima the following 
elements of the 35d cycle were obtained:

      Min X-ray = 2441347.86 + 35.396d.E

      The phases psi of the 35d cycle were then calculated and the
light curves with P=1.70017d for different intervals of psi were 
constructed. These light curves are essentially different for different  
psi's. The maximal amplitudes (12.8m-15.1m pg) are observed at

                       [FIGURE 1]

psi = 0.95-0.15 (left part of the Fig.) as well as in the middle of
the 35d cycle at psi = 0.55-0.65 (12.8m-15.0m pg). At the phases psi=0.25-
-0.55 the light curve becomes more flat, its minimum is more broad
and the range is 13.2m-14.6m pg (right part of the Fig.). There are
probably more narrow phase intervals where the amplitude is still
smaller.
    Therefore the X-ray maximum (psi = 0.5) coincides with the minimal
light amplitude i.e. minimal reflecting effect as it was suggested
by Cherepashchuk et al. (1972) and Lyutiy et al.(1972).   
    There are also humps on the light curves moving systematically
with psi. The detailed data are to be published in "Variable Stars"
Vol. 18, No. 5 1973.
    I am grateful to Yu.N. Efremov, B.V. Kukarkin, B.V. Komberg  and
R.A. Sunyaev for helpful discussion.

Moscow, December 1972.

                                  N. KUROCHKIN


References:

Cherepashchuk A.M., Efremov Yu.N., Kurochkin N.E., Shakura N.I.,
   Sunyaev R.A., 1972, IBVS No. 720.
Gursky H., 1972, Preprint.
Kurochkin N.E., 1972, Astr.Circ. USSR, No. 717. [BIBCODE 1972ATsir.717....1K ]
Lyutiy V.M., Sunyaev R.A., Cherepashchuk A.M., 1972, Preprint.