COMMISSION 27 OF THE I.A.U.
       INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 102


                                    Konkoly Observatory
                                    Budapest
                                    22 July 1965

                   RU MONOCEROTIS


   Photoelectric observations of RU Mon made by Prof. Bok and
myself in Nov. 1964 - Jan. 1965 at Mount Stromlo and Siding
Spring Observatories revealed very significant deviations of
the times of minima from the existing ephemerides amounting to
eight hours. The motion of the line of apsides is faster than
it was previously supposed, i.e. 45 arcsec per period of revolution.
U/P = 29000.
   The proposed formulae for minima are as follows:
Primary min. = hel. JD 2429641.567 + 3.5846391d * (E-3554) 
- 0.429d cos(alpha) + 0.060d sin (2alpha) + 0.010d cos (3alpha) + 
0.003d sin (4alpha)
Secondary min. = hel. JD 2429639.775 + 3.5846391day * (E-3554)
 + 0.429d cos (alpha) + 0.060d sin (2alpha) - 0.010d cos (3alpha)
 + 0.003d sin (4alpha)
where alpha = 0.01245deg * (E-406)
   For the next two years we can use the approximate formulae:
Primary Min. = hel. JD 2438732.098 + 3.5847111d ( E-6090 )
Secondary min. = hel. JD 2438730.606 + 3.5845259d ( E-6090 )
The durations of minima are respectively D1 = 4.9h, D2 = 10.1h (1)
their depths:  A1 = 0.73mag, A2 = 0.59mag.
   The next 5-7 years will be critical for exact determination
of the motion of the line of apsides and of the suspected variations 
of the orbital eccentricity ( between 0.36 and 0.39 ).
   Photometric, especially photoelectric observations are
strongly needed. The star "e" ( AN 235; 226, 1929) should be
avoided as a comparison star.

   1 July 1965
                           D. Ya. MARTYNOV
                         Sternberg Institute,
                              Moscow