COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3324

                                          Konkoly Observatory
                                          Budapest
                                          5 May 1989
 
                                          HU ISSN 0374 - 0676


                  THE VARIABILITY OF HD 73819


The star HD 73819 is one of the UBV standard stars in the Praesepe cluster
(Johnson 1952; Henden and Kaitchuck 1982). During a recent multi-site
campaign, HD 73819 was one of two comparison stars used for V filter photometry
of the nearby delta Scuti star HD 73756. Throughout the campaign, photometry
carried out with the 0.5m telescope at the Devon Astronomical Observatory
showed persistent variability in the V magnitude difference between HD 73819
(C2) and HD73711 (C1) that appeared to be modulated over time. Attempts to
attribute this variation to either changes in sky conditions or electronics
have proven unsuccessful and we are led to suggest that HD 73819 is
intrinsically variable.

The following four panels illustrate the variability of V(C1) minus V(C2) on
the nights of February 10/11, 16/17, 18/19 and 21/22, 1989. A least-squares
spline has been fitted to the data and is shown on each panel. The variation
in (C1-C2) is clearly modulated and significant with respect to the scatter in
the data. Typical scatter was +-2 mmag. Subsequent period searches within the
data sets (Variable-C1), (Variable-C2) and (C1-C2) suggest that the variation
in the (C1-C2) signal is due entirely to variability in HD 73819. The fourier
transform of the entire (C1-C2) set, spanning approximately 30 hours over 7
nights, reveals multiple significant frequencies centered at approximately 5.82
cycles/day. All of this indicates that HD 73819 may, in fact, be a multi-mode


                             [FIGURE 1]
                             [FIGURE 1b]


variable which warrants further observations. A fundamental period of
approximately 4.12 hours and a spectral type of A6 are suggestive of a delta
Scuti variable.


BRIAN E. MARTIN and DOUGLAS P. HUBE
Department of Physics
University of Alberta
Edmonton, Alberta
Canada T6G 2J1

References:

Henden, A.A. and Kaitchuck, R.H., 1982, Astronomical Photometry (Van Nostrand
   Reinhold Co., New York). [BIBCODE 1982asph.book.....H ]
Johnson, H.L., 1952, Astrophysical Journal 116, 640. [BIBCODE 1952ApJ...116..640J ]