COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1946

                                    Konkoly Observatory
                                    Budapest
                                    1981 April 1

                                    HU ISSN 0374-0676


       PHOTOMETRIC VARIABILITY OF KAPPA CASSIOPEIAE


  Kappa Cassiopeiae (HR 130, HD 2905, B1 Ia, V = 4.15) has a long
history of suspected velocity and light variability. Most recently,
Elst (1979) has reported light variability with a period of 0.09028d
(about 2h) and an amplitude (as judged from his Figure 1) at least
0.06m in blue light. Such variability, if interpreted as pulsation,
implies a very small Q-value and a very high overtone.
   In view of this theoretical implication, kappa Cas was observed on
seven nights in November 1980, using the #4 0.4 m telescope at Kitt
Peak National Observatory, near Tucson, Arizona. The telescope was
equipped with a single-channel photometer, with a dry-ice-cooled
1P21 photomultiplier and pulse-counting electronics. A high-quality
3m neutral density filter was used to reduce the number of counts, in
order to eliminate coincidence corrections. Observations were made
through a Stromgren b filter, relative to HR 146 and HR 244. These
observations, corrected for differential extinction and reduced to the
sun, are shown in Figure 1.

                           [FIGURE 1]

 Figure 1:  Light variability of kappa Cas, relative to HR 146, in blue
            light. The lower panel demonstrates the constancy of the
            comparison stars HR 146 and HR 244.

On the first six nights, the hour-to-hour light variability in kappa
Cas is no greater than that in the comparison stars.  Note that on the
sixth night, the scatter is greater (+-0.005m) in both kappa Cas and the
comparison stars, than it is on the other five nights (+-0.003m).  On
the seventh night, kappa Cas faded smoothly by 0.030m in 0.26d.  The 
comparison stars remained constant.  Thus there is no evidence for light
variability in kappa Cas with a period of 0.1d, and with an amplitude >0.01m.
An amplitude of 0.06m is certainly ruled out, at least in November 1980.
On the other hand, there is conspicuous light variability with a
period of about 7d and an amplitude of 0.05m. This period is close to 
that which would be expected due to the pulsation of a B1 Ia star
(Burki 1978, but see also Maeder 1980 for a more detailed discussion
of supergiant variability).
Several other B supergiants were also observed along with kappa Cas:
5 Per, 9 Per, HR 1040, 55 Cyg, 9 Cep, 13 Cep and 26 Cep. In each case,
there was no hour-to-hour variability  >0.01m, but in each case, there
was day-to-day variability of a few hundredths of a magnitude. Such
variability is often observed in B supergiants (Burki 1978).
On the other hand, hour-to-hour variability is not common in B
supergiants; in kappa Cas, it is either sporadic or non-existent.

Acknowledgements. I am grateful to the staff of Kitt Peak National
Observatory for the use of the facilities and for their help and 
hospitality. Kitt Peak National Observatory is operated by the Association
of Universities for Research in Astronomy, Inc., under contract with
the National Science Foundation. I also thank the Natural Sciences
and Engineering Research Council of Canada for their support of this
research.


                         JOHN R. PERCY
                         Erindale College and
                         Department of Astronomy
                         University of Toronto
                         Toronto, Canada M5S 1A7

References:


Burki, G. 1978, Astron. Astrophys. 65, 357. [BIBCODE 1978A&A....65..357B ]
Elst, E. 1979, I.A.U. Inf. Bull. Var. Stars # 1697.
Maeder, A. 1980, Astron. Astrophys. 90, 311. [BIBCODE 1980A&A....90..311M ]