COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2672


                                 Konkoly Observatory
                                 Budapest
                                 21 February 1985

                                 HU ISSN 0374 - 0676





           TIMES OF MAXIMUM LIGHT OF THE DELTA
                  SCUTI STAR CY Aqr




 Recently Rolland et al. (1985), and Purgathofer and Schnell (1984) carried
out an analysis of the Delta Scuti star CY Aqr including not only their 
observations, but a compilation of about 350 times of maximum light. With these
times of maxima, that covered a time span of about fifty three years they
concluded that the best ephemeris was

       T_max = HJD2440892.6370 + 0.0610381318 E - 4.58x10^-13 E^2.

  New observations were carried out at the 1 m telescope of the Observatorio
de Tonantzintla, Puebla, Mex., with a two-channel high-speed photometer in the
white light and an integration time of ten seconds to achieve the highest
accuracy possible in determination of the times of maximum light. The star
was observed on the nights of 21, 28 and 29 December, 1984.
 When these maxima were included in the analysis similar to that described
in Rolland et al. (1985) the results were the following :

       T_max = HJD2440892.63705 + 0.0610383201 E - 4.45x10^-13 E^2.

 Table I shows the residuals of the O-C analysis and Figure 1 shows 
graphically their corresponding values.


                Table I
Observed times of maximum light of CY Aqr in 1984
-------------------------------------------------
Times of max.light                O-C
(HJD-2400000.0)    Epoch    (day)     (min)
-------------------------------------------------
46055.5612         84 585   0.0010    1.435
46062.5806         84 700   0.0010    1.438
46063.5571         84 716   0.0009    1.320
-------------------------------------------------

 We feel that this and other stars of this kind have to be monitored 
continuously to decide unequivocally on its accurate period variation.

                          [FIGURE 1]

 Figure 1 : O-C vs time diagram with the ephemeris derived in the present
            study. The O-C axis is in units of day fraction whereas the
            abscissa, time is in days/1000.

  We would like to thank D. Flores for his assistance in the Heliocentric
correction, to A. Garcia for the drawing and to R. Escamilla for the typing.
J. Miller proofread the text.



                          J. H. PENA
                          R. PENICHE
                          Instituto de Astronomia - UNAM
                          Apartado Postal 70-264
                          04510 Mexico, D.F., Mexico

                          M. A. HOBART
                          Facultad de Fisica
                          Universidad Veracruzana
                          Apartado Postal 270
                          Xalapa, Ver.

References :

Purgathofer, A., and Schnell, A. 1984, Information Bulletin on Variable Stars No. 2500.
Rolland, A., Pena, J.H., Lopez de Coca, P., Peniche, R., and Gonzalez, S.F.
          1985, Submitted to the Astronomy and Astrophysics. [BIBCODE 1986A&A...168..125R ]