COMMISSION 27 OF THE I. A. U.
	INFORMATION BULLETIN ON VARIABLE STARS
		    Number 2335
						     Konkoly Observatory
						     Budapest
						     16 May 1983
						     HU ISSN 0374-0676

		XY Leo AND THE STAR BD+18d2304

XY Leo (BD+18d2307) is a well-known W Ursae Majoris system, which has
undergone a large number of period changes. A recent period study (Gehlich,
et al., 1972), using photoelectric observations made in 1971, found a period
of 0.28411d. De Carlo and Sabatini (1967) discovered that the nearby star
BD+18d2304 is an eclipsing binary having a period of 0.290d. The close 
proximity of the two systems (0.5d apart), their similar periods, and the similarity
in the depths of the eclipses in each system suggest the possibility that
De Carlo and Sabatini may have observed XY Leo and misidentified it as
BD+18d2304.
To test this hypothesis both XY Leo and BD+18d2304 were observed on five
nights during the spring of 1983 using the 41cm reflector of the Morgan-Monroe
Station of the Goethe Link Observatory. Johnson UBV filters were used with
a 1P21 photomultiplier tube cooled with dry ice. The comparison star used
was BD+18d2306. Between sky and comparison star readings, observations of
both XY Leo and BD+18d2304 were made. For XY Leo the Hertzsprung method was
used to determine times of minimum light from the observations in each filter.
These results were averaged and are presented in the Table I.


         Table I
------------------------
Hel. J.D.   Min   (O-C)
2440000+
------------------------
5396.6566   I	  0.0001
5416.6904   II	  0.0051
5444.6685   I	 -0.0004
5449.6432   II	  0.0026
------------------------


The residuals were calculated using the light elements published by Kaluzny
and Pojmanski (1982), namely:

Min. I = 2445074.4906 + .2840969d E

Our primary minima are consistent with these light elements, but our secondary 
minima show a displacement. Gehlich   et al., noted a smaller, time-varying 
displacement in the secondary.
The complete light curve of XY Leo was observed, thus if BD+18d2304 is a
variable having a similar period, variations in its brightness should have
been apparent. However, the magnitude of BD+18d2304 as determined with each
filter remained constant within 0.05m. From this we conclude that BD+18d2304
is not an eclipsing binary and suggest that De Carlo and Sabatini unknowingly
observed XY Leo.





	       DANNY R. FAULKNER,
	       DANIEL H. GROSSOEHME

	       Astronomy Department
	       Swain Hall West 319
	       Indiana University
	       Bloomington, IN 47405
	       U.S.A.





References:

De Carlo, R. and Sabatini, G. 1967, Inf. Bull. Var. Stars No. 193
Gehlich, U.K., Prolss, J., and Wehmeyer, R. 1972, Astr. and Astrophys.
  18, 477 [BIBCODE 1972A&A....18..477G ]
Kaluzny, J, and Pojmanski, G. 1982, Inf. Bull. Var. Stars No. 2181