COMMISSION 27 OF THE I. A. U.
	  INFORMATION BULLETIN ON VARIABLE STARS
		      Number 2649


			 	   Konkoly Observatory
				   Budapest
				   27 December 1984

				   HU ISSN 0374 - 0676

	THE OPTICAL BEHAVIOUR OF THE POLAR AM Her IN 1984



  On the base of the sequence of comparison stars given by Hudec and Meinunger
(1977) the star was measured on 160 blue-sensitive (ORWO-ZU21+GG13+BG12) and
on 17 photovisual (ORWO-RP1+GG14) plates from 53 nights taken with the 50/70/172
cm Schmidt camera of Sonneberg Observatory covering the time interval between
1984 March 3 and 1984 November 29. In 37 nights more than one plate per night
were obtained.
  The long time light curve in B and V are shown in Figure 1. Like in the
series of the years 1982 and 1983 two different states of the brightness
behaviour of AM Her can be seen there. Concerning the active state, which is
characterized by increased brightness caused by X-ray heating it is remarkable
that the mean brightness amounts to B~14.0m +-0.5m. This brightness behaviour which
is similar to that of the series 1982 and 1983 is situated about 1.2 mag below
the known maximum brightness obtained from sky patrol plates and known from
the long time light curve of former years given by Hudec and Meinunger (1977).

  Numerous plates are obtained in the low state of the star. They permit to
study the occultation light changes in that state.
  A relationship given in Figure 2 was found between the measured B magnitudes
and the derived colour indices B-V. The diagram, where increasing brightness
goes with decreasing colour index contains also the data of the flare, which
was observed in 1983 (Gotz, 1984a) and in its lower part photometric 
observations published by Mazeh, Kieboom and Heise (1983).

  The circles drawn in Figure 2 represent mean colour indices from more than
one determination per night while colour indices (B-V) which which were derived from
nearly synchronous observations of our own series (B) and visual estimations
given by Verdenet (1982-1984) are marked by crosses. But up to now the given
relationship is still incomplete especially in the lower ranges of brightness.

  In order to study the influences of occultation light changes to the overall
light curve, all observations were reduced by means of the improved orbital
elements.
                          [FIGURE 1]
                          [FIGURE 2]
                          [FIGURE 3]
                          [FIGURE 4]

	Min_hel=244 5406.576+0.12892737d*E   (Gotz, 1984b)
the one common epoch.
  The result is given in Figure 3, where the mean magnitudes B obtained 
separately from all observations of the high and the low states plotted against
the phases. The number of observations used from each state are drawn in.
From Figure 3 it can be seen that in the low state the minimum phase is 
displaced to ph=0.35.

   The behaviour of the colour indices caused by the occultation light changes
is shown in Figure 4. There, the mean colour indices (B-V)_occ obtained reducing
the observational data to B=14.5m by means of the given colour magnitude
relation are plotted against the phases. The result is nearly in agreement
with that given by Priedhorsky and Krzeminksi (1978). After that the largest
colour indices can be expected at the phase ph~0.30 while the lowest values
are attributed to the minimum phase.





		       W. GOTZ
		       Akademie der Wissenschaften
		       der DDR, Zentralinstitut fur
		       Astrophysik, Sternwarte Sonneberg




References:

Hudec, R., Meinunger, L., 1977, MVS 7, 194
Gotz, W., 1984a, IBVS No. 2459
Gotz, W., 1984b, MVS 10, 69
Mazeh, T., Kieboom, K., Heise, J., 1983, IAU-Circ. No. 3892 [BIBCODE 1983IAUC.3892....2M ]
Verdenet, 1982-1984, AFOEV
Priedhorsky, W.C., Krzeminski, W., 1978, ApJ 219, 597 [BIBCODE 1978ApJ...219..597P ]