COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1949

                                   Konkoly Observatory
                                   Budapest
                                   1981 April 6

                                   HU ISSN 0374-0676


         NEW LIGHT ELEMENTS OF TY URSAE MAJORIS


   The variability of the short period eclipsing system
TY UMa was discovered by Beljawsky (1933). The following
light elements, obtained on the basis of photographic 
measurements, are reported in the literature:


Min I = helioc. J.D.2427283.443+ 0.3010392d  n   Zverev (1933)
		      27360.375+ 0.3011424         "    (1937)
		      38112.392+ 0.3011432       GCVS   (1968)
		      39651.447+ 0.3011424       Gotz   (1969)

  Several hundred photoelectric B and V observations were
made at the Merate Observatory during the year 1967. By least
squares fitting of a parabola to observations the following
times of minimum were derived:
	
	helioc. J.D.2439532.4971   2439614.3955
        	        532.6727       643.4673
	                561.5685       648.4306
        	        562.4545       673.4247
                	563.5179       676.4407
	                566.5328       681.4023

   From these values the new light elements follow:

(1) Min I = helioc. J.D. 2439532.67350 +- 0.35453989d n
                              +-     4            19 m.e.

  The period P_s = 0.30114d is not really the true one P, but
a related period rising from the likely unfavourable time
distribution of the measurements. The 1 day interval of 
observations and the period P give rise to spurious periods
(Renson, 1980):                     

       P_s^-1=P^-1 +-1 j^-1         (j=integer)      

With the above values the equation is fulfilled with j=2.
  The twelve photoelectric instants were then combined, in a
weighted least squares solution, with twenty visual or 
photographic times given in the literature to derive the ephemeris
given below:

(2) Min I = helioc. J.D. 2439532.6741 + 0.35453694d n
                              +-    6           33 m.e.

The difference between the periods (1) and (2) is larger than
the corresponding mean errors. However considering the short
interval encompassed by photoelectric observations (about 150
days) we can only question a variation of the period. New B
and V observations now in progress at the Merate Observatory
will help to settle this point and to see if TY UMa undergoes
seasonal light curve variations.



                      P. BROGLIA and P. CONCONI
                      Osservatorio Astronomico
                         22055 Merate, Italy


References:

Beljawsky, S., 1933, NNVS 4, 196.
Gotz, W., 1969, MVS 5, 67.
Renson, P., 1980, Astron. and Astrophys. 92, 30. [BIBCODE 1980A&A....92...30R ]
Zverev, M., 1933, NNVS 4, 235.
Zverev, M., 1937, NNVS 5, 108.