COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 391

                             Konkoly Observatory
                             Budapest
                             1969 October 16


           OO Aql - AN ECLIPSING BINARY
          WITH RAPIDLY SHORTENING PERIOD

      At the University-Observatory of Izmir 2 
photoelectric minima of the eclipsing variable OO Aql (W UMa-
type) were obtained during the last months. The O-C's against
the elements, given in GCVS 1958 (I) and SAC 40, 1969 (II)
are increasing (see table). New elements were calculated by
the method of least squares (III and IV).
      In the table the minima 1.3 and 4 are normal minima,
calculated from 16, 28 and 12 visual determined minima
(published in IBVS). The Observers are: Ashbrook, Baldwin
Cook, Howell, Monske, Lowder and Williams. The other minima
are photoelectric, 2 from Pohl, number 5 and 6 from Ibanoglu
and Kurutac.
      The calculation with all 6 minima gives the elements
III; the O-C_III show clearly, that the period has shortened
between JD 2437 000 and 2440 000. From minima 3 to 6 I have
obtained the elements IV, which gave very small O-C's
may be valid at present time.

No. Minima JD.    O-C(I) O-C(II) O-C(III) O-C(IV)
         
1 2437 200.532   -0.011d +0.001d  -0.008d
2   38 239.466   -0.009  +0.007   +0.006
3   39 300.681   -0.025  -0.006   +0.003   -0.001d
4   39 714.728   -0.030  -0.010   +0.003   +0.001
5   40 068.4638  -0.038  -0.0166  -0.0011  -0.0002
G   40 366.4544: -0.044  -0.0211: -0.0031: -0.0002:


I  Min JD 2434 226.4113+0.50679597d   E (GCVS 1958) 
II "    "   37 192.4222+0.506794387   E (SAC 40, 1969)
III"    "   37 200.540 +0.50679006  E      (Pohl)
IV "    "   39 300.682 +0.5067868  E       (Pohl)



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