COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 2851

                                         Konkoly Observatory
                                         Budapest
                                         21 January 1986

                                         HU ISSN 0374 - 0676




          OPTICAL BEHAVIOUR OF THE POLAR AM Her IN 1985



  In linking to the sequence of comparison stars given by Hudec and Meinunger
(1977) the star was measured on 115 blue-sensitive (ORWO-ZU 21 + GG13+ BG12 )
and 10 photovisual (ORWO-RP1+ GG14) plates from 42 nights taken with the
50/70/172 cm Schmidt camera of Sonneberg Observatory covering the time interval
between 16 February and 5 December 1985. On 29 nights more than one blue
plate per night was obtained. The individual observations will be published
in MVS, Sonneberg.
  In addition, 12 B-V colour indices on 8 nights could be derived. They
complete the colour- magnitude diagram (m(B) - B-V) given by Gotz (1984b) and
are in agreement with the behaviour shown there. The individual colour indices
are listed in Table I.

     Table  I:

J.D.hel.
244....         B         B-V

6175.456       15.55m     0.52m
6175.501       15.25      0.35
6200.408       15.60      0.50
6200.448       15.45      0.40
6327.337       15.47      0.32
6327.358       15.50      0.35
6328.345       15.55      0.35
6328.366       15.55      0.35
6374.238       15.05      0.50
6385.243       15.34      0.39
6386.259       15.45      0.63
6387.282       15.35      0.45

  The long-time light curve in B and V (open circles) is given in Figure 1.
As in the series of other years (1982, 1983, 1984 - see Gotz, 1982, 1984a)
two different states of brightness behaviour of AM Her can be seen there.
But most of the observations are from the low state which is characterized
in 1985 by two long-lasting minima of 55d and more than 120d, respectively.
The observations of the high state which is caused by X-ray heating are starting


                            [FIGURE 1]


from the mean brightness B =~ 14.0m on the way down to the low state 
in two cases.
   The occultation light changes from the high state observations superimposed 
on the long-time behaviour of AM Her are in agreement with the improved 
orbital elements given by Gotz (1984b).





                               W. GOTZ

                       Zentralinstitut fur Astrophysik
                       der Akademie der Wissenschaften
                               der DDR
                          Sternwarte Sonneberg





References:

Gotz, W., 1982, IBVS, No. 2226.
Gotz, W., 1984a, IBVS, No. 2459.
Gotz, W., 1984b, IBVS, No. 2649.
Hudec, R. and Meinunger, L., 1977, MVS, 7, 194.