COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1082
                   

                                 Konkoly Observatory
                                 Budapest
                                 1976 January 15



                 INACTIVE STATE OF HZ Her


   At Sonneberg Observatory there exist a number of 90 cm 
astrograph plates of the inactive state of Her X-1= HZ Her in the
time intervals 1934 April 15 to August 7 (J.D. 2427543...7657)
and 1937 April 6 to 1940 June 8 (J.D. 2428630...9789), This 
communication includes the results of a more thorough investigation
of that state, than has been given in Mitt. Verand. Sterne Sonneberg 
6, p. 61 ff, because it had turned out in the meanwhile that
those plates are the only material which can lead to a rather precise 
light curve of the inactive state (this is the state in which
HZ Her exhibits brightness variations of only small amplitude, 
unlike to the "normal" active state where a reflection effect of
large amplitude is present). HZ Her has been in an active state for
the past 17 years.
   From our material we find that the light curve of the inactive 
state is a pure eclipsing one, reflection effect or ellipsoidal
variations being completely absent. The amplitude of this eclipsing
light curve is m_pg = 19.60m - 15.15m; in the normally active state
the range is roughly 12.90m - 14.80m and depends on the 35 day cycle
phase.
   Primary and secondary minima of the inactive curve are of nearly 
equal depth, but the secondary minimum is very broad, 0.3p,  as
compared with the primary one (0.1p).  This is an evidence for the
existence of absorbing matter - the accretion disk - around the  X-
ray star, the disk being not self-luminous, but absorbing.
   Our inactive light curve shows an asymmetry:
The center of the secondary minimum is situated approximately  at
phase 0.56 of the 1.7d variation. This asymmetry can be explained
by either an asymmetric shape of that absorbing accretion disk  or
by an excentric orbit of the system.
    Processing of the series of observations on Sonneberg 
astrographic plates yields the following most probable elements:

       Primary min. = 244 1397.584 + 1.700175d . E

The inactive light curve does not show any evidence for the 35d
X-ray, cycle, shape and amplitude of the light curve being 
independent of the 35d phase, unlike the variations in the normal
active state.
    The change from the inactive to the active curve and vice
versa occurs in the course of a few days.


                           [FIGURE 1]

           The inactive state light curve of HZ Her:
           (triangle) - J.D. 242 7543 ... 7657
           (circle) - J.D. 242 8630 ... 9789


WOLFGANG WENZEL                          RENE HUDEC

Central Institute for Astrophysics       Astronomical Institute of
of the Academy of Sciences of GDR,       the Czechoslovak Academy
Sternwarte Sonneberg GDR                 of Sciences,
                                         Observatory Ondrejov
                                         Czechoslovakia