COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1688

                                    Konkoly Observatory
                                    Budapest
                                    1979 October 16





            NEW ELEMENTS FOR AP LEONIS



    The eclipsing binary AP Leonis was discovered by Strohmeier
and Knigge (1961) and was observed by H. Mauder (1967) during the
years 1966-67 and the photometric and geometric elements were 
determined.
    In 1978 and 1979 we have observed AP Leonis through B and
V-filters with 50-cm telescope of Bucharest Observatory. Using
the observations in B obtained in. 1978, the photometric and 
geometric elements have been calculated; the approximate solution
resulted from  Horak-type model (1970), while the improved 
solution was obtained with a Wood model (1972). It was confirmed
that an annular type of eclipse occurs at primary minimum and a
total type eclipse during the secondary minimum. The results are
given in Table and in Fig. 1 where the observations (normal
points) are represented by crosses.

                   Table
Adjusted parameters       Fixed parameters
i = 83.131+- 0.01      T_1(eq)       = 6000dK
r_1= 0.5866 +- 0.04          q       = 0.211
k = 0.534+- 0.03       beta_1=beta_2 = 0.25
T_2(eq) = 6161+-217dK  x_1=x_2       = 0.6
                       w_1=w_2       = 0
                       n_1=n_2       = 5.0

       Auxiliary parameters
a_1= 0.6355            a_2= 0.3395
b_1= 0.5980            b_2= 0.2851
c_1= 0.5263            c-2= 0.2631
T_1(pol)=6608dK        T_2=(pol)=6586dK
L_1(app)=0.862         L_2(app)=0.215
L_1(norm)=0.800        L_2(norm)=0.200


    The coefficients x_1, x_2 and the temperature T_1 correspond
to the spectral classes dG0 + G2 of the stars: The mass ratio
was fixed at the value obtained in a first approximation. Six
iterations were necessary for the convergence of the solution
with the model by Wood.

                        [FIGURE 1]
                        [FIGURE 2]

    Comparing our observations with those by Mauder (Fig.2 where
points are Mauder's observations, while circles and crosses are
ours) one can see a change in the secondary maximum. The difference 
in magnitude between the values obtained in 1966-67 and
1978-79 is about 0.06.
    The work concerning the interpretations of the observations
in V filter is in progress as well as new improvements of model.
More observations are needed in the future in order to determine
more precisely the features of the light curve and the physical
conditions in the system.



                            C. CRISTESCU
                            G. OPRESCU
                            M. D. SURAN
                    Center for Astronomy and Space
                             Sciences




References:
Horak, T.B., 1970, A.J. 75, 10, 1116 [BIBCODE 1970AJ.....75.1116H ]
Mauder, H., 1967 Ver.Bamberg, VII, No. 61
Strohmeier, W., Knigge, R., 1961, AN, 286, 133 [BIBCODE 1961AN....286..133S ]
Wood, D.B., 1972, Goddard Space Flight Center, X-110-72-473