COMMISSION 27 OF THE I.A.U.
               INFORMATION BULLETIN ON VARIABLE STARS
                            Number 1445

                                                      Konkoly Observatory
                                                      Budapest
                                                      1978 July 3


 BD +47d842 - AN ULTRASHORT PERIOD DELTA SCUTI VARIABLE

In a recent survey of the alpha Persei cluster to detect
small amplitude variables, three new such variables were 
discovered which are members of the cluster, as reported by
Slovak (1978). These variables were classified as delta Scuti
pulsators, falling within the confines of the delta Scuti 
instability strip and displaying the short period, small amplitude
variations which characterize the class. Of particular interest 
is BD +47d842 (V = 8.78, B-V = +0.28; A3V), the hottest
pulsator to be discovered in the a Persei cluster, which is
found to fall nearly on the blue edge of the instability strip.
An analysis of the 1975-1976 differential data has revealed
this variable to be multi-periodic, having a "fundamental"
period of P = 0d.070 and an "overtone" period of P1 = 0d.030.

                      [FIGURE 1]

   In order to achieve higher time resolution, BD +47d842
was examined in 1977 November using a two channel high speed
photometer which continuously samples the program star in the
first channel and a suitable comparison star in the second channel. 
The light curve obtained in this fashion on 1977 Nov 4
is shown in the accompaning figure. The data were obtained on
the 76-cm telescope of the McDonald Observatory; each point
represents the average counting rate (in instrumental magnitudes)
obtained in unfiltered light over a 10s integration period.
The data have been corrected for the sky background and extinction, 
using a mean coefficient of k_vis = 0.350. Clearly visible
in the light curve are two nearly symmetrical pulsations with
a peak-to-peak amplitude of = 0.017 mag, having a mean period
of 0d.0295 = 42.5 minutes. Thus, the "overtone" period P_1 has
been present in BD +47d842 for at least two years, revealing
it to be a remarkably stable pulsator. For study of similar
short period Delta Scuti variables, the application of the technique 
of high speed photometry, as opposed to the classical
method of differential photometry, promises to be a powerful
tool for defining the exact nature of the complicated light
curves of these complex stars.


  MARK H. SLOVAK                 JOHN AFRICANO

Department of Astronomy       McDonald Observatory
  University of Texas          University of Texas



Reference:

Slovak, M. H. 1978, Ap. J., in press. [BIBCODE 1978ApJ...223..192S ]