COMMISSION 27 OF THE I. A. U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                              Number 2469

                                                       Konkoly Observatory
                                                       Budapest
                                                       6 February 1984

                                                       HU ISSN 0374-0676



            PERIOD CHANGE OF THE ECLIPSING BINARY IM AURIGAE


  Photoelectric observations and improved elements of this binary were
reported by Gudur et al. (1982). These elements were as follows:

         Hel Min JD = 2438327.7922 + 1.2472906 * E
                              +-11         +-3      (1)
  We obtained two new photoelectric minima with the 48 cm Cassegrain telescope
of the Ege University Observatory. These new minima are given in Table I
together with all collected photoelectric ones published up to date. The
O-C values in this table were computed with equation (1).

                     Table I
               Times of minima of IM Aurigae
JD Hel         Min     O-C       E        Reference
2438327.7867   I     -0.0055    0       Kondo,1966
    345.873    II    -0.0050   14.5          "
    380.803    II     0.0010   42.5          "
    385.788    II    -0.0030   46.5          "
    700.7403   I      0.0083   299           "
    769.3316   I     -0.0014   354      Margoni et al.1966 
  40515.5465   I      0.0067   1754     Dworak,1974
  42749.4434   I      0.0062   3545     Dworak,1976
  44517.4706   II    -0.0009   4962.5   Gudur et al.1982
    567.3674   II     0.0043   5002.5        "
    569.236    I      0.0020   5004          "
    893.5270   I     -0.0027   5264          "
    931.5674   II    -0.0046   5294.5        "
  45018.2548   I     -0.0042   5364     This paper
    261.4702   I     -0.0104   5559          "


  The O-C values in Table I are plotted in Figure 1. As it can be seen from,
the figure, the O-C values of recent minima show a rapid decrease. This is
probably due to the abrupt change in the period after 1980. Therefore, we
recalculated the light elements of the system by the method of weighted least
squares using only four primary minima obtained by us. These new light
elements are as follows:


        Hel Min I JD = 2444893.5267 + l.2472681d*E
                                +-2        +-12        (2)



                              [FIGURE 1]

 Figure 1   The O-C values computed with the elements given by equation (1)

                              [FIGURE 2]

          Figure 2   The O-C diagram obtained from equation (2)


The O-C values computed with the equation (2) are shown in Figure 2. These
new light elements can be used with sufficient accuracy in prediction of
the times of minima for the near future.





            O. GULMEN, C. SEZER and N. GUDUR
            Ege University Observatory
            Bornova-Izmir-Turkey





References:

Dworak, T.Z.: 1974, Inform.Bull.Var.Stars, No. 916
Dworak, T.Z.: 1976, Inform.Bull.Var.Stars, No. 1081
Gudur, N., Gulmen, O. and Sezer, C.: 1982, Inform.Bull.Var.Stars, No. 2098
Kondo, Y.: 1966, Astron.J., 71, 46 [BIBCODE 1966AJ.....71...46K ]
Margoni, R., Mammano, A., Biolchini, R. and Bartolini, C.: 1966, 
  Inform.Bull.Var.Stars, No. 131