COMMISSION 27 OF THE I.A.U.
              INFORMATION BULLETIN ON VARIABLE STARS
                           Number 1217

                                             Konkoly Observatory
                                             Budapest
                                             1976 December 13


        REMARK ON THE PERIOD OF AU MONOCEROTIS

From a series of photoelectric observations, L. Lorenzi
(1) has determined four epochs of primary minimum of AU Monocerotis. 
Taking furthermore into consideration the other visually
observed primary minima, he determined a rapid cyclic variation
of the orbital period. In this way, Lorenzi concluded "AU Mon
shows unusually rapid fluctuations in the epochs of minima; if
these fluctuations can be represented by a formula of type (7),
the only possible physical interpretation is an apsidal motion".
   Now, having in view the very short value of the apsidal
period (P_aps.= 243.23d?) and the general difficulties concerning
apsidal period determination, we propose new series of observations 
which could be done in the winter of the next year.
  - In order to resume the corresponding cyclic variation
    which was found by Lorenzi, new primary minima could be observed
    in February - March of the next year.
  - In order to prove the presence of apsidal motion, 
    secondary minima must be observed. The coming winter and spring
    (January - May) are very suitable for such observations.
  - As the corresponding orbital period is P = 11.11306d,
    there are few suitable nights for observations in a season,
    that is why an extensive co-operation is very much required.
  - In order to stimulate the interest of the observers for
    this star, we give here the corresponding ephemeris for the
    two kinds of minima.

Lorenzi's elements are used :

         M(E) = 2442801.3602 + 11.11306d E


        Primary minima      Secondary minima
          J.D.hel               J.D.hel

        2443112.526         2443118.082
            123.639             129.195
            134.752             140.309
            145.865             151.422
            156.978             162.535
            168.091             173.648
            179.204             184.761
            190.317             195.874
            201.430             206.987
            212.543             218.100
            223.656             229.213
            234.770             240.326
            245.883             251.439
            256.996             262.552
            268.109             273.665
            279.222             284.778


                               IOAN TODORAN

                         Astronomical Observatory
                         Cluj - Napoca, Romania



Reference:

Lorenzi, L. 1976, Astron. and Astrophys. 29, 10, 1976 (in press)