COMMISSION 27 OF THE I. A. U.
      INFORMATION BULLETIN ON VARIABLE STARS
                  Number 1786

                              Konkoly Observatory
                              Budapest
                              1980 May 16


        REVISED PHOTOMETRIC ELEMENTS OF Y Leo

Table

lambda     7900
i          85.3+-.2
r_h        .218+-.006
k          1.281+-.030
a_h        .220
b_h        .219
c_h        .217
a_c        .327
b_c        .275
c_c        .254
T_h (eq)   8800
T_h (pol)  8860
T_c (eq)   4400+-40
T_c (pol)  4490
u_h        .38
u_c        .55
beta_h     .25
beta_c     .08
w_h        1
w_c        .5
L_h        .911
L_c        .089
q          .3
epsilon    1.27

The light variations of the Algol-type eclipsing binary Y Leo has been studied
photoelectrically by Johnson in 1960 in four wavelength regions (UBV and
infrared). Struve (1945) obtained a single-lined radial velocity curve.

We solved the (most complete) infrared lightcurve of Y Leo obtained by Johnson
(1960) by means of WINK Wood's model (1972, 1973-1978). In the table we list
our new photometric elements (for the explanation of the symbols see
Mardirossian et al.(1980)). The chief variable parameters are the orbital
inclination angle i, the unperturbed radius r_h of hotter component, the ratio
k=r_c/r_h of the unperturbed radii, and the temperature T_c of the cooler
component. The temperature T_h of the hotter star was taken equal to 8800degK
according to the spectral type type A3 and Flower's (1977) temperature scale.
The mass ratio q=M_c/M_h was taken to be equal to 0.3; this value was estimated
from Struve's (1945) mass function f(m)=0.038 M_sun together with the
assumption that the primary obeys the empirical mass-spectrum relation typical
of main sequence stars (M_h=2.6 M_sun).

Our photometric elements appear to be in substantial agreement with those
computed by Johnson (1960) by means of Russell and Merrill's (1952) method. Y
Leo is confirmed to be an ordinary semidetached system, practically free of
complications. The temperature of the lobe filling secondary favours an early
K spectral type.


G. GIURICIN, F. MARDIROSSIAN, and F. PREDOLIN
Osservatorio Astronomico di Trieste
via G.B. Tiepolo 71
I-34131 Trieste (Italy)

References:

Flower, P.J., 1977. Astron. Astrophys. 54, 31 [BIBCODE 1977A&A....54...31F ]
Johnson, H.L., 1960, Astrophys. J. 131. 127 [BIBCODE 1960ApJ...131..127J ]
Mardirossian, F., Mezzetti, M., Predolin, F., and Giuricin, G., 1980, Astron.
   Astrophys. Suppl. 40, 57 [BIBCODE 1980A&AS...40...57M ]
Russell, H.N.,and Merrill, J.E., 1952, Princeton Contrib. 26 [BIBCODE 1952deeb.book.....R ]
Struve, O., 1945, Astrophys. J. 102, 74 [BIBCODE 1945ApJ...102...74S ]
Wood, D.B., 1972,  A Computer Program for Modeling Non-Spherical Eclipsing
   Binary Systems, Greenbelt, U.S.A.
Wood, D.B, 1973-1978, WINK Status Report No. 1-9, priv. com.