COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1880

                                    Konkoly Observatory
                                    Budapest
                                    1980 December 5

                                    HU ISSN 0374-0676



       SUPPLEMENTARY OBSERVATIONS OF AR Lac IN 1974



After the detection of radio outbursts in the RS CVn type eclipsing 
binary AR Lac by Hjellming and Blankenship (1973), there was
a concentration of observations on this object in 1974 and the
following years. Chambliss (1976) published photoelectric broad
band photometry obtained between 1972 and 1974. Weiler (1978)
carried out photoelectric spectrophotometry of the H and K and
H_alpha line regions. Previous detailed spectroscopic investigations
are available by Sanford (1951), and Naftilan and Drake (1977).
Various authors looked succesfully for emission line variability
of Hydrogen and Ca II.
This paper reports some results of 131 photoelectric measurements
in V, obtained from May 29 to August 7, 1974 (JD 2442197-2442267)
and 55 spectra obtained from June 1 to November 7, 1974
(JD 2442200-2442359). The photoelectric measurements have been
obtained with the 36 cm Cassegrain telescope of Hoher List Observatory; 
the spectra have been taken with the Cassegrain
spectrograph at the 106 cm telescope of Hoher List Observatory.
The spectra cover a range of 3800 Ang. to 4900 Ang. with a dispersion
of 29 Ang./mm.
The photoelectric measurements (Fig.1), plotted and compared
with those by Chambliss, fill some of the gaps of this light
curve. Of particular interest are the phases 0.72 and 0.47.
Hall et al. (1976) claimed a minimum of the suggested RS CVn-
wave like distortion in AR Lac at phase 0.72 in 1974. The measurements 
shown here do not confirm this result. They form a
smooth light curve from phase 0.6 to 0.8 showing only the small
curvature by the aspect changes of the slightly distorted components. 
On the other hand, an interpolation between the 


                       [FIGURE 1]

 Figure 1.: V observations of AR Lac reduced to the comparison
 star used by Chambliss (1976). The central line of Chambliss'
 observations is plotted as solid line.


measurements at phases 0.25 and 0.40 favour a lower first maximum
of the light curve. Thus the analysis of the wave like distortion 
in AR Lac should be treated as preliminary for the 1974
entry.
Weiler reported an unusual decrease of the H and K emission line
strength at phase 0.47 and interpreted it as eclipse effect of
an active region on the secondary. The measurements shown here
indicate a depression of the light curve around the first contact
of the secondary eclipse. These measurements have been made at
JD 2442197 and 2442201, 3.5 months apart from Weiler's observations. 
At JD 2442205 a spectrogram taken at phase 0.44 shows
an unusually weak emission profile of the secondary components
Ca II K line (the H line is less suited for such conclusions because 
of the blending with the Hepsilon line). After phase 0.52 the
1974 light curve is the maximum of the three observation series
by Chambliss, leading to an inclined transit minimum. It is suggested 
that all these phenomena are related to the same origin,
indeed most probably the existence and eclipse of an active area
on the secondary. This shall not exclude that also the Ca II
emitting primary exhibits magnetic activity too.
The spectra, which are well spread over the phases with exception
of a gap between 0.25p and 0.43p, unfortunately do not show a significantly 
established variation of individual line strengths
between the differently bright maxima or at phase 0.08 when
Chambliss' 1974 measurements indicate another depression.
At primary minimum there seems to be a faint emission of H_beta, as
found by Naftilan (1975) for RS CVn and discussed by Naftilan
and Drake (1976). This is virtually enhanced at phase 0.03, probably 
because of a mixture of the first H_beta absorption parts of
the other component emerging from eclipse and the weaker Fe
line at lambda4859.7 Ang. of the secondary. Blending with Fe lines prevents 
a conclusion on emission in the Balmer lines of higher order.




                           M. HOFFMANN
                       Observatorium Hoher List
                       5568 Daun / Eifel, BRD



References:
Chambliss, C.R., 1976, Publ.Astr.Soc. Pacific 88, 762 [BIBCODE 1976PASP...88..762C ]
Hall, D.S., Richardson, T.R., and Chambliss, C.R., 1976,
        Astron. J. 81, 1138 [BIBCODE 1976AJ.....81.1138H ]
Hjellming, R.M., and Blankenship, L., Nature Phys.Sci. 243, 81 [BIBCODE 1973NPhS..243...81H ]
Naftilan, S.A., 1975, Publ.Astr.Soc. Pacific 87, 321 [BIBCODE 1975PASP...87..321N ]
Naftilan, S.A., and Drake, S.A., 1977, Astrophys. J. 216, 508 [BIBCODE 1977ApJ...216..508N ]
Sanford, R.F., 1951, Astrophys. J. 113, 299 [BIBCODE 1951ApJ...113..299S ]
Weiler, E.J., 1978, Monthly Notices Roy. Astron. Soc. 182, 77 [BIBCODE 1978MNRAS.182...77W ]