COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1794

                                   Konkoly Observatory
                                   Budapest
                                   1980 May 27


             THE BINARY SYSTEM BS DRACONIS


The binary system BS Draconis was observed at the Cluj Observatory from March
3, 1972 to August 18, 1974. The observations in B and V have been made with a
50-cm Newton telescope equipped with unrefrigerated 1P21 photomultiplier.

The mean light curve in V obtained from 498 points is given in Fig. 1, where
the observations have been represented by crosses. This curve has been used to
determine the elements.

                         [FIGURE 1]

A preliminary solution (Model 1) has been obtained using a Horak-type model;
for rectification the Fourier development has been derived: l=0.9805+0,0065
cos Theta-0.0046 cos 2 Theta+0.0010 sin Theta-0.0026 sin 2 Theta. The results
are given in Table I. The preliminary solution has been improved using a Wood
model. First taking into account the equal amplitude of the two minima and the
spectroscopic results it was assumed that the mass ratio q=1. The results
(Model 2) are given also in Table I and are plotted in Fig. 1 (full line).
Then q has been computed (Model 3), and the value obtained is very close to 1,
i.e. q=0.99. From the three models, model 2 seems to be the best solution,
giving the smallest (O-C)_2. During the principal minimum there is a total
eclipse, while during the secondary - an annular eclipse.

Table I

Variable parameters  Model 1    Model 2       Model 3

i deg               90.0197   89.783+-0.006   90.000+-0.008
r_1                  0.1035   0.1099+-0.002   0.1096+-0.002
k                    1.1111   1.0581          1.0625
T_2(eq) deg          6379     6443+-32        6442+-34
q                    -        -               0.9920

Constant parameters

T_1(eq) deg          6500     6500           6500
u_1=u_2              0.6      0.6            0.6
beta_1=beta_2        -        0.25           0.25
w_1=w_2              -        0.5            0.5
n_1=n_2              -        5              5
q                    -        1              -

Auxiliary parameters

a_1                  0.1036   0.1101         0.1098
b_1                  0.1035   0.1099         0.1096
c_1                  0.1034   0.1098         0.1094
a_2                  0.1156   0.1166         0.1167
b_2                  0.1148   0.1163         0.1164
c_2                  0.1146   0.1161         0.1162
T_1(pol) deg         -        6509           6509
T_2(pol) deg         -        6453           6453
L_1(ap)              -        0.0305         0.0303
L_2(ap)              -        0.0329         0.0329
L_1(norm)            0.4667   0.4809         0.4790
L_2(norm)            0.5332   0.5191         0.5210
                     0.0346   0.0219         0.0220

The complete solution, including the light curve in B, will be published
elsewhere.


D. CHIS, C. CRISTESCU, G. OPRESCU, M.D. SURAN, I. TODORAN
Center of Astronomy and Space Sciences, Bucharest and Cluj
and
V. POP
University Babes - Bolyai
Cluj