COMMISSION 27 OF THE I. A. U.
             INFORMATION BULLETIN ON VARIABLE STARS
                           NUMBER 83

                                        Konkoly Observatory
                                        Budapest
                                        2 February 1965


             VARIABILITY OF THE RADIO SOURCE CTA -102

     During the period from August 1964 to February 1965 
measurements of the flux densities of CTA-21 and CTA-102 were made,
at the wavelength 32.5 cm with the aid of a modulation radiometer,
The flux densities of both sources have been determined relative to
3C-48. It should be noted, that according to recent spectral measurements 
the radio flux density of 3C-48 is constant within 3% [1].
     In the figure the determined ratios of the flux densities -
CTA-21/3C-48 and CTA-102/3C-48, together with those obtained
from previous measurements [2, 3] have been plotted against time.
One can see, that the ratio CTA-21/3C-48 remains constant within the
errors of measurement, while the ratio CTA-102/3C-48 varies at
least within 0.320-0.430; these limits are far in excess of the errors
of measurement.

                           [FIGURE 1]

     The flux density of CTA-102 varies roughly according to a
sinusoidal law with a period close to 100 days. Variations with shorter
periods may be also present. The linear diameter of the source cannot
exceed the value cT ~= 0.1 parsec - 2.10^4 a.u. Compared with the
angular diameter of CTA-102, Theta = 0".01, obtained by the method presented 
in [4], an upper limit for its distance can be determined: R <= 2
megaparsec. This can be considered as the indication of the galactic
origin of CTA-102.

1   Matthews, T. A., Sandage, A.R., Astrophys. J., 138, 30, 1963. [BIBCODE 1963ApJ...138...30M ]
2   Harris, D. E., Roberts, J. A., Publ. Astron, Soc. Pacific, 72, 237, 1960. [BIBCODE 1960PASP...72..237H ]
3   Conway, R.G., Kellerman, K.I., Long, R.J., Mon. Not. Roy.
    Astron. Soc., 125, 261, 1962. [BIBCODE 1963MNRAS.125..261C ]
4   Slish, V. I., "Nature", 199, 628, 1963. [BIBCODE 1963Natur.199..682S ]



                            G. B. SHOLOMITSKY
                     Sternberg Astronomical Institute
                                  Moscow