COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2181

                                  Konkoly Observatory
                                  Budapest
                                  1982 July 29

                                  HU ISSN 0374-0676





   NEW TIMES OF MINIMA AND THE PERIOD VARIATIONS OF THE
             W UMa-TYPE VARIABLE XY Leo



The short period eclipsing variable of W Ursae Majoris type,
XY Leo (BD +18d2307) was observed with a photoelectric unrefrigerated 
photometer attached to the 60 cm Cassegrain telescope at
the Ostrowik station of the Warsaw University Observatory. The
observations were made through B,V filters and reduced to the
Johnson system. BD +18d2306 was used as a comparison star. Five
times of minimum were obtained from observations performed 
between March 1981 and April 1982, and they are given in Table I.

                   Table I

           New times of minima of XY Leo


  JD Hel.         E      (O-C)
(2440000+)
4694.3710(3)   32419.    0.0195
4702.4638(3)   32447.5   0.0154
5017.5286(5)   33556.5   0.0101
5056.4514(2)   33693.5   0.0106
5074.3486(5)   33756.5   0.0095

The (O-C) values were calculated from the light elements given
by Gehlich et al. (1972):

    Min I = JD Hel. 2435 484.0222 + 0.28410282dE         1.

On the basis of our observations we have computed the new 
elements using the least-squares method, obtaining:

    Min I = JD Hel. 2445 074.4906 + 0.2840969dE          2.

A large difference (O-C) between primary and secondary minima
was observed in 1981. All photoelectric times of minimum light
available for us were collected, and the (O-C) values were
calculated from the equation 1. Times of minima observed after
1972 are listed in Table II,



             Table II
Times of minimum light of XY Leo observed after 1972
JD Hel.          E     (O-C)    Ref.
(2440000+)
2051.6196    23117.    -.0075   1
2099.4896    23285.5   -.0085   1
2841.4395    25897.    0.0066   2
3193.7325    27137.    0.0121   3
3193.876:    27137.5   0.014    3
3198.705:    27154.5   0.013    3
3198.8465    27155.    0.0123   3
3567.7564    28453.5   0.0146   4
3572.7288    28471.    0.0152   4
3606.396:    28589.5   0.016    5
3612.6462    28611.5   0.0161   4

References:

1-Burchi et al. (1975), 2-Pohl and Kizilirmak (1977), 3-Hilditch
(1981), 4-Koch and Shanus (1978), 5-Pohl and Gulmen (1981)

References to earlier observations are collected by Gehlich et
al. (1972). Period variations of XY Leo were interpreted by
Gehlich et al. as due to presence of a third body in the system.
The "third body" (O-C) sinusoid proposed by these authors is
marked by dashed line in Figure 1.

                     [FIGURE 1]

We can see that (O-C) residuals for 20 000<E<30 000 lie about
0.01d under this line. This fact was observed by Pohl and
Kizilirmak (1977), and by Koch and Shanus (1978).
The other possibility mentioned by Gehlich and his co-workers
is that period variations of XY Leo demonstrate sudden changes.
Assuming that the period between the jumps is constant they
derived the least squares fit: P1=0.28410714d and P2=0.28409807d,
for 1949-1959 and 1959-1970 intervals, respectively. For 1970-
1980 and 1980-1982 intervals, we obtained: P3=0.28410734d and
P4=0.2840969d, respectively. The (O-C) residuals calculated for
afore mentioned periods are plotted in Figure 2.

                      [FIGURE 2]

Full light curves of XY Leo in 1981 and 1982 seasons will be
published in Acta Astronomica.





           J. KALUZNY, G. POJMANSKI
           Warsaw University Observatory
           Al. Ujazdowskie 4
           00-478 Warszawa
           Poland

References:

Burchi, R., Zavatti, F. 1975, I.B.V.S. No. 964
Gehlich, U.K., Prolss, J. and Wehmeyer, R. 1972, Astron.
   Astroph. 17, 477 [BIBCODE 1972A&A....18..477G ]
Hilditch, R.W. 1981, M.N.R.A.S. 196, 305 [BIBCODE 1981MNRAS.196..305H ]
Koch, R.H. and Shanus, C.R. 1978, A.J. 83, 1452 [BIBCODE 1978AJ.....83.1452K ]
Pohl, E., Gulmen, O. 1981, I.B.V.S. No. 1924
Pohl, E. and Kizilirmak, A. 1977, I.B.V.S. No. 1358