COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                   Number 2226

                                Konkoly Observatory
                                Budapest
                                1982 November 11

                                HU ISSN 0374-0676





   SOME REMARKS ON THE CLOSE BINARY X-RAY SOURCE AM Her





  In studying the long time behaviour the star was inspected
on 56 blue-sensitive plates (ORWO-ZU 21 + GG13 + BG 12) taken
with the 50/70/172 cm Schmidt camera of Sonneberg Observatory
covering the time interval between 1982 April 15 and 1982 
September 24. The exposure time of these plates varies between 5
and 30 minutes. In 11 nights more than one exposure per night
were obtained. The used sequence of comparison stars in B is
given by Hudec and Meinunger (1977).
  The long time light curve in B is shown in Figure 1.


                         [FIGURE 1]


There, the plotted estimations from Schmidt plates (.) are
supplemented and completed by observations on blue-sensitive
sky patrol plates (o) of Sonneberg Observatory and by visual
observations (+) published by Verdenet (1982), Mattei (1982)



and Magalhaes (1982) and reduced to B according to the statements
of Patterson and Price (1980) and Szkody (1978).
  In the long time light curve of Figure 1 two different states
of the behaviour of AM Her can be seen. The low state could be
observed from 1982 April 15 to 1982 April 27; according to the
light curve it could not have lasted longer than 4 weeks and
was thus extremely short. This state is identical with the inactive 
state of the system which is characterized by minimum
brightness of AM Her at about B = 15.3m. In this state the amplitude
of the occultation light curve is very small.
  The high and active state of AM Her is closely combined with
the increase of brightness caused by X-ray heating. In such
phases the star can keep a maximum brightness of approximately
B ~ 13.0m with variations of about 0.5 mag on the average (Hudec,
Meinunger). In the given long time light curve the high state
is characterized by a broad band of observations between B ~ 13.5m
and B ~ 14.4m beginning at 1982 May 13 after the low state. Also
remarkable is the well pronounced decline from the high to the
low state.
  In order to study the influences of occultation light changes
to the overall light curve, in particular at the high state, all
observations, were reduced by means of the orbital elements

      min.hel. = 244 5180.440 + 0.12892774d. E
                        
to one common epoch.
  The result is given in Figure 2 where the magnitudes mB are
plotted against the phases. The activity of the orbital period,
given by Szkody, Raymond and Capps (1982), can be confirmed
evidently at the high state. The mean occultation light curve
in B (marked by circles) is in conformity with that given by
Szkody (1978). In the low state, however, no periodical 
variation can be seen in our observations because of their small
amplitude and of the long exposure times of the plates used.


                         [FIGURE 2]


  More details about the behaviour of AM Her in the past year
will be published in MVS. We thank Mr. Boller, guest student at
our observatory, for taking a series of plates at the Schmidt
camera.

            W. GOTZ

            Akademie der Wissenschaften 
            der DDR Zentralinstitut fur
            Astrophysik, Sternwarte
            Sonneberg


References:

Hudec, R., Meinunger, L., 1977, MVS 7, 194
Magalhaes, A.M., 1982, IAU-Circ. No. 3698 [BIBCODE 1982IAUC.3698....1M ]
Mattei, J.A., 1982 IAU-Circ. No. 3689 [BIBCODE 1982IAUC.3689....2M ]
Patterson, J., Price, C., 1980, PASP 93, 71 [BIBCODE 1981PASP...93...71P ]
Szkody, P., 1978, PASP 90,61 [BIBCODE 1978PASP...90...61S ]
Szkody, P., Raymond, J.C., Capps, R.W., 1982, Ap.J. 257, 686 [BIBCODE 1982ApJ...257..686S ]
Verdenet, M., 1982, IAU-Circ. No. 3693 [BIBCODE 1982IAUC.3693....3V ]