COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1194

                              Konkoly Observatory
                              Budapest
                              1976 October 26




      THE LIGHT VARIATIONS OF THE Ap STAR HD 134793





     The magnetic field of the Ap star 134793 was found to be
of moderate intensity by Babcock (1958), who also put in 
evidence magnetic polarity reversals and large spectral changes in
the Eu II and Sr II lines into a period of the order of two days.
Spectroscopic observations by Bonsack (1974) give evidence of
large variations in the line intensities of Ca II, Si II, Mg II
and Eu II.
     The V magnitude and the colours of this star have been
determined by Abt and Golson (1962). A period of 2.7806 days has
been determined by Maitzen (1976) from his photoelectric 
observations.
     Photoelectric observations of HD 134793 have been carried
out at the 91 cm telescope of the Catania Astrophysical Observatory 
from 1970 to 1973 in our natural system (lambdaU_eq = 3500 Angstrom+- 300;
lambdaB_eq = 4370 +- 450; lambdaV_eq = 5440 +- 300) obtaining 95 measurements in
U, 89 in B and 83 in V., The magnitude differences HD 134793 -
HD 134827 versus the phase computed by the elements:
          JD (V light max) = 2441060.5d +- 2.78d E
are plotted in the Figure. Each point represents the mean value
of an average number of eight single measurements. It is remarkable 
that the V variation goes in opposition of phase with respect 
to the U and B ones.
     The observations by Bonsack (1974) seem to agree with
the above value of the period but more spectroscopic and magnetic 
observations are needed to determine the behaviour of the
line intensity variations and to establish their phase relation
with the magnetic field and light variations.

                       [FIGURE 1]


               C. BLANCO, F.A. CATALANO and G. STRAZZULLA

                     Osservatorio Astrofisico
                     citta universitaria
                     95125 Catania, Italia

References:

Abt, H.A., Golson, J.C. 1962, Astrophys.J. 136, 35 [BIBCODE 1962ApJ...136...35A ]
Babcock, H.W. 1958, Astrophys.J.Suppl. 3, 141 [BIBCODE 1958ApJS....3..141B ]
Bonsack, W.K. 1974, Publ.Astron.Soc.Pacific 86, 408 [BIBCODE 1974PASP...86..408B ]
Maitzen, H.M. 1976, in "Physics of Ap Stars" IAU Coll. 32,
      ed. W. Weiss (in press)