COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1103

                                     Konkoly Observatory
                                     Budapest
                                     1976 February 18


          PHOTOELECTRIC OBSERVATIONS OF delta CETI


    A Beta CMa variable, delta Ceti was observed photoelectrically in
yellow and blue lights at the Ege University Observatory in December 
1974 and January 1975. The observations were carried out
with the 48 cm Cassegrain telescope with an unrefrigerated 1P21
photomultiplier. The wavelength, maximum permeability, half width
and thickness of the used filters are given in Table 1.

                          Table 1
Colour       Wavelength   max. Per.     HW       Thickness
             (Angstrom)     (% )    (Angstrom)      mm
  B            4350         64         920          8
  V            5550         53         860          7

   BD - 0d 378 was used as the comparison star.
   In each colour 5 light curves were obtained which have 5
maxima. In the observed values, the necessary reduction and 
corrections were made.
Average amplitudes of light curves were calculated as
follows:
             A_B    =    0.034m
                           +-2
             A_V    =    0.032m
                           +-2
   The magnitude differences, measured on December 11, 1974,
were transformed to the UBV system. We used the transformation 
coefficients given by Ibanoglu* (1974). The light curve on this night
is shown in Fig. 1. The magnitude which we found in UBV system, as
follows:


* Ibanoglu obtained the transformation coefficients in the same
  condition, like ours.

             m (B)     m (V)
        max: 3.919m    4.127m
        min: 3.959m    4.161m

              (B-V) = -0.209m
                         +-4

   Jerzykiewicz (1970), has given the light elements for this
star as:
       Max.Blue Light JD Hel.= 2438385.6860+ 0.16113800d E
                                        +-8        +-25
   The calculated max.times, due to Jerzykiewicz (1970),  and
our observed max. times-and (O-C)_max.t. values are given in Table 2.

                              Table 2
Observed max.t.       Calculated max.t.         (O-C)_max. t.
2442393.3543            2442393.3492              +0.0051d
    419.2855                419.2924              -0.0069
    428.3162                428.3161              +0.0001
    430.2537                430.2498              +0.0039
    431.2233                431.2166              +0.0067

  (O-C) values given in Table 2, are plotted against time, and
the (O-C) variation fitted approximately to sinecurve, as given in
Fig. 2.

    The new light elements which were found, are:

Max.Blue Light JD Hel.= 2442428.316 + 0.16113800d E + a sin 2Pi t/P,
                                                 (or, a sin 2Pi E/236).
  Here, a =~ 0.007d amplitude of (O-C) variation
  P'=~ 38d =~ 236 E period " "     " "
  t = number of days after JD 2442428.3161

    We consider to study further on the same object for finding
the reliability of our results.


                            ZEYNEL TUNCA

                          Ataturk University
                          Faculty of Sciences
                          Erzurum - Turkey


                     [FIGURE 1]
                     [FIGURE 2]

References:

 Ibanoglu, C. 1974, A.Ap.Supp. 13, 119. [BIBCODE 1974A&AS...13..119I ]
 Jerzykiewicz, M. 1970. Lowell Obs. Bull. No. 155. 7, 189.