COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                 NUMBER 303


                          Konkoly Observatory
                          Budapest
                          1968 October 15



                 BD +28deg637


      On the basis of the photometric material obtained
in 1960-64 at the Schmidt camera in three colours of the
UBV system (80 photos in each colour) we found that the
star BD +28deg637 is an irregular variable.
      The extreme values of its brightness are as follows:
11.69-13.40, 11.30-12.41, 10.55-11.53 mg in U,B and V,
respectively. The colour indices vary in wide range: (U-B)
from +0.35 to +1.32, (B-V) from +0.51 to +1.65.
      On the (U, U-B) diagram a short-wave emission 
excess appears with the increase of the brightness of the
star.
      On the Hertzsprung-Russel diagram the star is
located within the T-band. The star BD +28deg637 is probably
a variable of the RW Aur type.

October 1, 1968.
                        L.N. MOSIDZE

                Abastumani Astrophysical Observatory
                      Georgian SSR, USSR



            THE LIGHT-SURFACE OF TU Cas


      TU Cas is a cepheid type variable with regular
light curve variation. The periods were determined by
Oosterhoff (1): P = 2.1393d and P_B = 5.2306d.
      The variable was observed at the Konkoly Observatory
in three colours from 1960 until 1963. Using a procedure
proposed by J. Balazs and L. Detre (2) we constructed the so
called light-surface of the variable. It proved to be
similar to that of the RR Lyrae stars showing Blashko effect
(e.g. AR Her) (3): on the light-surface of TU Cas a bulb
appears and develops on the descending branch, whilst the
brightness of the maximum decreases resulting in a double
maximum at a definite phase of the P_B-period; later the old
maximum is shrinking to a bulb on the ascending branch,
finally disappearing, meanwhile the new one, increasing
continuously, is shifted to the left and takes the place of
the old maximum.
      The phenomenon repeats itself in all the three
colours and could be checked independently from the 
observations of Vasilanovskaja (4) as well.



                             E. ILLES
                        Konkoly Observatory
                             Budapest




Literature:
   1 Oosterhoff, P.Th.: BAN XIII. No 479. (1967).
   2 Balazs, J. - Detre, L.: Budapest Mitt. 8 (1939). [BIBCODE 1939CoKon...8....1B ]
   3 Almar, I.: Budapest Mitt. 51 (1961). [BIBCODE 1961CoKon..51....1A ]
   4 Vasilanovskaja, O.P.: Bjull.Stalinabad No 43-44
     (1966).