COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1184

                              Konkoly Observatory
                              Budapest
                              1976 October 5



       ACTIVE AND INACTIVE STATE OF AM Her = 3U 1809+50


   The preliminary results of the observations on 700 Sonneberg
archiv plates from years 1928-1976 show that the variable star
AM Her, the optical candidate for the high galactic latitude X-
-ray source 3U 1809+50, exhibits two different states in its
long-time light curve. During the first of them (we call it 
active state) is AM Her approximately m_pg~12.8m bright and shows
probably small amplitude light variations of 0.3m in the time
scale of approximately 200 days or more. During the inactive
state AM Her is roughly m_pg~ 14.2m faint. The inactive state was
found in the following intervals:
J.D. 2427150-7310, J.D. 2428200-8450, J.D. 2430700-0900,
J.D. 2431300-1620, J.D. 2432800-3500, J.D. 2439020-9230 and
J.D. 244 1570-1700.
   The Figures show two selected parts of the long-time 
variations of AM Her on our plates.
   The existence-of two different states of AM Her is similar
to the other high latitude X-ray source HZ Her=Her X-1. Probably
these variations are caused by a mechanism like that in the
HZ Her system, i.e., the X ray heating and reflection effect.
The short-time variations (eclipsing light curve) with very
broad secondary minimum as compared with the primary one of
AM Her (Cowley et al., IAUC 2984) are similar to the HZ Her 
inactive state light eclipsing variations (Wenzel and Hudec, IBVS
No. 1082), too. Thus, the optical behaviour of AM Her supports
strong evidence to the identification AM Her=X-ray source
3U1809+50. However, the orbital period of AM Her system is
only 186 min. (Cowley et al., IAUC 2984) as compared with HZ Her
(1.700175 day; Wenzel and Hudec IBVS No.1082) and so the light
curve obtained from the plates (expos. from 30 to 180 minutes)
cannot show the detailed short-time eclipsing variations, but
only the mean brightness with smaller variations.

                    [FIGURE 1]


R. HUDEC                           L. MEINUNGER
Astronomical Institute of          Central Institute for Astrophysics
Czechoslovak Academy of Sciences   of Academy of Sciences
Observatory Ondrejov,              of GDR, Observatory
Czechoslovakia                     Sonneberg, GDR