COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 546

                                Konkoly Observatory
                                Budapest
                                1971 May 8


                    RY TAURI

      A mean light-curve of this RW Aur-type star has
been constructed from Tsessevich's observations performed
on Harvard Sky Patrol plates and from Moscow and Odessa
plates (Fig. 1). There is one big and slow fluctuation of
brightness with a very long cycle, besides there are
smaller superposed oscillations. We have determined the
length of individual cycles and plotted them in Fig. 2. It
is clear that the cycles get shorter as the mean brightness
of the star increases. The cycles vary within the limits of
500 to 2500 days.
      There are also rapid fluctuations. When the star
gets brighter we observe short Algol-like weakenings
(Fig. 3). If the brightness of the star gets fainter, its
behaviour changes: we observe rapid flares (Fig. 4),
      The comparison of photographic and visual observations 
shows that the visual magnitude is not a simple
function of the colour-index. The relationships between the
two quantities for different time intervals are given in
Fig. 5 and in the following Table:



----------------------------------------------
       Interval       Relationship
                      between V and CI
----------------------------------------------
  I   2425209-2427358    m_v = 11.89 - 1.91 CI
 II   2427407-2428170    m_v = 10.72 - 1.51 CI
III   2428441-2429326    m_v = 10.58 - 1.01 CI
 IV   2437254-2438734    m_v = 12.09 - 1.59 CI
  V   2439022-2439480    m_v = 15.57 - 4.95 CI
----------------------------------------------



Odessa Astronomical Observatory
1971 January 30            B.A. DRAGOMIRETSKAIA
                           V. TSESSEVICH



              [FIGURE 1]

              Fig. 1.
    General mean light-curve of RY Tauri



              [FIGURE 2]

              Fig. 2.
C: length of cycle, E: serial number of cycle.
  Dotted line: curve of mean brightness.


              [FIGURE 3]
              [FIGURE 4]
              [FIGURE 5]