COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 2735

                                       Konkoly Observatory
                                       Budapest
                                       27 May 1985

                                       HU ISSN 0374 - 0676



    OPTICAL BEHAVIOUR OF THE POLAR ST LEONIS MINORIS = CW 1103 + 254


   ST LMi belongs to the group of AM Her type stars (Liebert and Stockman,
1984) and is a cataclysmic variable binary system containing a strongly
magnetic white dwarf primary. Its finding chart is given by Shore et al.
(1982).
   The star was measured and inspected on 69 blue-sensitive plates (ORWO-
ZU21+GG13+BG12) from 43 nights taken with the 50/70/172 cm Schmidt camera of
Sonneberg Observatory covering the time interval between 30 May 1983 and
24 April 1985. On 16 nights more than one plate per night were obtained. The
exposure time of the plates amounts to 20 minutes.
   The identification chart is shown in Figure 1 and the sequence of the
comparison stars in B is listed in Table I. The magnitudes of these stars
were obtained on two plates by linking them to the UBV sequence of the Coma
region given by Argue (1963).

                            Table I

          Comparison     mB          Comparison     mB
           star                        star

            a        14.61mag          e          16.57mag
            b        15.07             f          16.88
            c        15.49             g          17.10
            d        16.22

   The long time-scale light curves in B from the seasons 1983/84 and 1984/85
are shown in Figures 2 and 3. Similarly to other AM Her objects, two different
states of the brightness behaviour of ST LMi 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 mB~15.75mag.
On the contrary, the mean brightness of the low and inactive state of the star,
which was observed in the time interval between 3 December 1983 and 15 December
1983, amounted to mB~16.65mag.
   Both the light curve in the low state and that of the high state are
influenced by occultation light changes. In order to study these influences,


                              [FIGURE 1]
                              [FIGURE 2]
                              [FIGURE 3]

                              [FIGURE 4]


all observations of the high state were reduced to one common epoch by means
of the preliminary orbital elements:

           Min. Hel. = 244 5769.531+ 0.079 090d E
The result is given in Figure 4, where the individual observations (small
dots) and the mean magnitudes (large dots) are plotted against the phase.
More observations are needed to make statements about the behaviour of the
occultation light changes in the low state. Besides, it is noticeable that
the period of the occultation light changes corresponds to that given by
Liebert and Stockman (1984).

  The individual observations will be published in MVS.




                             W. GOTZ

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

References:
Argue, A.N., 1963. Mon. Not. R. astr. Soc., 127, 97. [BIBCODE 1963MNRAS.127...97A ]
Liebert J., and Stockman, H.S., 1984, Preprint No. 441 of Steward Obs. [BIBCODE 1985ASSL..113..151L ]
Shore, S.N., Foltz, C.B., Wasilewski, A.J., Byard, P.L., and Wagner, R.M.,
    1982, P.A.S.P., 94, 682. [BIBCODE 1982PASP...94..682S ]