COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                              Number 2958

                                                         Konkoly Observatory
                                                         Budapest
                                                         26 November 1986

                                                         HU ISSN 0374 - 0676


   Beta Cas: A PROBABLE SMALL AMPLITUDE MONOPERIODIC delta Sct STAR

Recently, the bright star Beta Cas (V=2.26, B-V=+0.35) and some other Delta Sct
stars have been observed with IUE. During the same period, photometric
observations of Beta Cas were carried out at the Merate Observatory in order
to get some indications on the modal content of the pulsation of this star.
710 measurements were performed during 8 nights from September 2 to October
4, 1986 with the 50 cm reflector using a standard V filter together with a
neutral filter. The comparison stars were nu^2 Cas (V=4.63, B-V=+0.96) and
nu^1 Cas (V=4.83, B-V=+1.21). For the frequency analysis we adopted the
least squares power spectrum technique (see Antonello et al., 1986), and we
obtained the period P=0.10101. d, which is slightly different from that given
by Millis (1966). The difference can be explained by the wrong cycle number
assumed by Millis between the first and the second maximum observed by
himself. Our period fits well these times of maximum.
   Considering P as known constituent we searched for a second period; however
we have not detected any significant peak in the power spectrum. This means
that there should not be a second period with a semi-amplitude greater than
0.001 mag. The P=0.10101 d explains 61% of the data variance and leaves a
r.m.s. residual of +-0.008 mag, i.e. the same obtained for the two comparison
stars. The full amplitude of the V-light curve of Beta Cas is 0.03 mag.
   Our results do not confirm the amplitude variations obtained with radial
velocity measurements (Yang et al., 1982). However, those observations were
made during one night and covered only two cycles.
   A detailed report on our observations and data analysis will be published
elsewhere.


                  E. ANTONELLO, L. PASTORI, E. PORETTI

                   Osservatorio Astronomico di Brera
                           Via E. Bianchi, 46
                       22055 MERATE (CO) - Italy



References:

Antonello, E., Mantegazza, L., Poretti, E.: 1986, Astron. Astrophys. 159, 269 [BIBCODE 1986A&A...159..269A ]
Millis, R.L.: 1966, Publ. Astron. Soc. Pacific 78, 340 [BIBCODE 1966PASP...78..340M ]
Yang, S., Walker, G.A.H., Fahlman, G.G.: 1982, Publ Astron. Soc. Pacific 94, 317 [BIBCODE 1982PASP...94..317Y ]