COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1033

                                 Konkoly Observatory
                                 Budapest
                                 1975 August 13


          THE ECLIPSING BINARY SYSTEM X Tri


  Three-colour photoelectric observations of the star X Tri
in the system close to U,B,V have been carried out by the 
telescope A3T-14 during 1969-1972.
  On the basis of these observations corrected elements were
obtained:
  Min_hel= 2437572.2149 + 0.9715288 E,
which were applied for the mean light curves' calculations.
  The mean light curves' rectifications followed Russell-Merrill's
technique. Photometric elements were calculated on the computer
"Nairi" after the programme of Lavrov's direct method. The elements
thus obtained are given in the Table.


         yellow blue   uv
---------------------------
k         0.870 0.861 0.865
r_1       0.329 0.328 0.327
r_2       0.286 0.283 0.283
i           90    90    89
L_1       0.145 0.099 0.127
L_2       0.855 0.901 0.873
J_2/J_1   7.8  12.2   9.9
x_1       0.5   0.5   0.5
x_2       0.5   0.5   0.5
---------------------------

The absolute parameters derived in yellow light are:

-------------------------------------------------------
 A    r_1  r_2  m_1  m_2  T_1  R_1  R_2 M_b1 M_b2   q
-------------------------------------------------------
5.91 1.94 1.69 1.05 1.89 5344 1.95 2.55 3.59 1.58  0.56
-------------------------------------------------------

The Roche model constructed exhibits that the sub-giant 
component fills its Roche lobe. The X Tri proves an example of a
typical semi-detached system, the cool component losing its mass.



                       M.I. KUMSIASHVILI
                       Abastumani Astrophysical
                       Observatory