COMMISSION 27 OF THE I. A. U.
                  INFORMATION BULLETIN ON VARIABLE STARS
                              Number 2459

                                                    Konkoly Observatory
                                                    Budapest
                                                    10 January 1984

                                                    HU ISSN 0374-0676



           THE LONG TIME BEHAVIOUR OF THE POLAR AM Her IN 1983



 The star was inspected on 92 blue-sensitive plates (ORWO-ZU 21 + GG 13 +
BG 12) from 36 nights taken with the 50/70/172 cm Schmidt camera of Sonneberg
Observatory covering the time interval between 1983 March 9 and 1983 November
6. The exposure time of these plates varies between 9 and 30 minutes, but
most of the plates are exposed 20 minutes. In 21 nights more than one plate
per night were obtained.
 The used sequence of comparison stars in B is given by Hudec and Meinunger
(1977). It is remarkable that concerning its brightness in 1983 AM Her has
steped over the limits of this sequence given by the comparison stars
q (m_B = 12.79m) and e (m_B = 15.44m).
 The long time light curve in B is shown in Figure 1. There, the estimations 
on individual plates are plotted by dots. The mean magnitudes from
nights with more than on plate are marked by circles.


                           [FIGURE 1]


 As in the series of the year 1982 (Gotz, 1982) two different states of
the behaviour of AM Her can be seen in Figure 1. Most of the time in 1983
the star spent in the active state which is characterized by increased
brightness caused by X-ray heating. In this phase where the influences of the
occultation light changes could be confirmed again a flare was observed on



July 12, 1983. There, the brightness of AM Her increased from m_B = 13.74m
(J.D. hel. 2445528.407) to m_B = 12.33m, delta m^b = -1.41m, within delta t = 0.024d. On a
plate in V (ORWO-RP1 + GG 14), which was exposed 29 minutes later than the
maximum plate the brightness of the star is V = 13.10m. From both plates a
colour index of B - V = -0.77m results. The inactive state of the star with
a brightness lower than m_b = 15.0m was observed at the end of the given series.
The change from the high to the low state started within 1d between 1983
October 4 (m_B = 14.16m) and October 5 (m_B = 15.05m).

  More details about the behaviour of AM Her, especially concerning the
occultation light changes will be published in Mitt.Verand. Sterne (Sonneberg).





                    W. GOTZ

              Akademie der Wissenschaften
              der DDR, Zentralinstitut fur
              Astrophysik, Sternwarte
              Sonneberg





References:

Hudec, R., Meinunger, L., 1977, MVS 7, 194
Gotz, W., 1982, IBVS No. 2226