COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 392
 
                              Konkoly Observatory
                              Budapest
                              1969 October 17

     A SPECTROSCOPIC STUDY OF THE ECLIPSING BINARY
                  R CANIS MAJORIS

      It is well known that the main feature of this
close binary system is that both components have too small
masses compared with those expected from their luminosities
or spectral types; it is also well known that the period
has abruptly shortened around 1914 and it is still
shortening. The results obtained from former observations
do not agree well and there is no reason to prefer any one
of the available orbits.
      Spectroscopic observations of this binary has been
done at the Observatory of Merate by the writer from January
1966 at a dispersion of 34 A/mm, and a new set of elements
has been derived from 17 plates without undertaking a least
squares solution. The results are the following ones:

      K = 26.0       a seni = 0.406 x 10^6
      V_0 = -45.5      f(m) = 0.0021
       
eccentricity assumed = 0.00. A new orbit has also been 
computed from all the 81 observations available, covering about
40 years, from the year of the sudden change of the period,
by means of the programme by Bertiau. The results are:

    K     = 23.07 +/- 2.61      P      = 1.1359 +/- 0.0015
    V_0   =-39.80 +/- 2.20      T_0    = 2432891.510 +/- 0.018
    e     = 0.046 +/- 0.104     f(m)   = 0.0020
    omega = 149.77deg+/- 1.85   a sen i= 0.391 x 10^6

      From the mass function computed in this way and 
assuming (Kitamura) for the primary component a normal F1 V
mass of 1.7 Sun, we deduced a mass ratio of 0.12; in this
case the radius of the secondary component exceeds its Roche
limit. If on the contrary, we assume that the secondary
fills exactly its Roche limit, we deduce a total mass of
only 0.31 with a mass ratio of 0.24. We may confirm in this
way the result by Kitamura of a mass loss through the
Lagrangian point L_2.
      Finally we notice that, the velocity V_0 of the center
of mass has diminished in a way that may be an evidence of
the existence of a third body with very long secondary
period.

Osservatorio Astronomico di Brera-Milano
                                               P. GALEOTTI
References:

Bertiau, I. A. U., Symp, n. 30, p. 227 [BIBCODE 1967IAUS...30..227B ]
Kitamura, Astrophys. and Space Science, 3, 163, 1969 [BIBCODE 1969Ap&SS...3..163K ]