COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1130

                                Konkoly Observatory
                                Budapest
                                1976 May 3



   Rothney Astrophysical Observatory Publication Series B, No. 3



           CAII H AND K EMISSION OF RT Lac


  Microdensitometer scans of 8 spectra of RT Lac, a 5.07d period eclipsing
binary similar to the RS CVn type binaries, were carried out at the University 
of Calgary. The spectra, all at the identical dispersion of 78 A mm^1
were obtained at the Dominion Astrophysical Observatory in 1974 between
JD 2442068 and 2442287.
  The light curve of this binary undergoes periodic changes due to a sinusoidal 
distortion wave which regresses through the light curve with a period
of about 10y. The location of the peak of the distortion wave relative to
the orbital period was obtained from an unpublished relation found by Hall
and Milone. At the time of the observations the peak corresponded to the
primary minimum of the binary.
  Our data (Fig. 1) suggest the preliminary result that the variation of
the CaII K emission intensity, as indicated by the ratio of the K2 component 
to the continuum, with phase, apparently reached a maximum at primary
minimum. The emission at CaII H defined in the same way was apparently
more uniform in phase (Fig. 1). These results contrast with the findings of
Weiler (1975) that the phases of maximum emission coincide with the minimum
of the wavelike distortion in the systems RS CVn and UX Ari. Studies are
continuing and a more complete discussion will appear elsewhere.


Rothney Astrophysical Observatory                   J.L. DROPPO
Physics Department, University of Calgary           E.F. MILONE
Calgary, Alberta, Canada
T2N 1N4



Reference:

Weiler, E.J. 1975, I.B.V.S. No. 1014


                        [FIGURE 1]

 Fig. 1. A measure of the H (open circles) and K (filled circles) emission
 in RT Lacertae plotted against phase of the distortion wave. Phase 0.0
 corresponds to the peak of the sinusoidal wave in 1974, and coincidentally
 with the primary minima.