COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1550

                                Konkoly Observatory
                                Budapest
                                1979 February 14




     OBSERVATIONS OF BRIGHT T Tau STARS IN NGC 2264


     Between December 16, 1972 and April 8, 1973 twenty exposures
of the young galactic cluster NGC 2264 were taken with the 6" 
refractor of the Wilhelm Foerster Observatory on Kodak 103 a-f film.
The limiting magnitudes of these exposures are between 14.5m and
15.3m V. Using the identification charts and V-magnitudes of Walker
(1956), the magnitudes of seven bright T Tau stars were determined
by the Argelander step method. Daily means of these magnitudes are
listed in Table 1, they are uncertain by about +-0.1m.
     Rapid variability by about 0.4m within half an hour is 
observed for IO Mon, MM Mon and S5192. LR Mon, MM Mon and MO Mon
showed brightness fluctuations of about 0.5m within some days.
IP Mon showed only slow variability and S5181 seemed to be constant
during these observations.



                            Table 1
-------------------------------------------------------------------------
Date (J.D.)   IO       IP     LR      MM       MO       S5181      S5192
-------------------------------------------------------------------------
2441668.3d             13.3   <13.5                                 13.2+
    681.3     13.8     13.7    13.9   13.7:    13.7      13.1       14.1:
    682.3     14.1:    13.6    14.0:  13.9:    14.0      13.3       14.3:
    685.3     13.9     13.6    14.3   14.4:    13.7+     13.4       14.3
    740.3     13.7     13.6    14.0   14.1     13.8      13.4       14.2
    758.3     13.8:    13.2   <14.3   14.0:    14.1:     13.5      <14.3
    764.3     13.6     13.5    14.0   13.5    <13.7      13.2      <14.0
    766.3     13.6     13.4    14.1   14.2:    14.1      13.2       13.9:
    772.3     13.8+    13.4    14.1:  13.9+    13.7      13.3       14.2:
    773.3     13.7     13.5    14.1   13.6     13.7      13.3       14.2
    781.3     13.7     13.4    14.1   13.8     13.6      13.3       14.1
-------------------------------------------------------------------------
+ rapid variability by 0.4m within half an hour observed




              U. HOPP, U. SURAWSKI
       Wilhelm - Foerster Observatory, Berlin



Reference:

Walker, M.F. 1956 - Astrophys.J.Suppl. 2, 365 [BIBCODE 1956ApJS....2..365W ]