COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3319

                                            Konkoly Observatory
                                            Budapest
                                            14 April 1989

                                            HU ISSN 0374 - 0676


            HD 181219 : A SUSPECTED ECLIPSING BINARY


HD 181219 is a star with a K0 spectral type and a V=7.86 magnitude, both taken
from the Henry Draper Catalogue. It was serving as the comparison star during
photometry of HD 181943 in an investigation by Hooten and Hall (1989) using the
Vanderbilt 16-inch automatic telescope. HD 181943 had appeared earlier on a
list of 90 suspected variables (Fekel and Hall 1985), where we see it has a
G8IV spectral type and a V=9.3 magnitude. Hooten and Hall noticed, from
several discordant differential magnitudes, that the comparison star was
occasionally faint by about 0.1 magnitude.

HD 181219 itself was observed differentially with respect to the check star HR
7379 (A1V, V=6.70m) from JD 2,447,277.93 to JD 2,447,434.62 and 70
differential magnitudes in V and B were obtained. These observations have been
corrected for differential atmospheric extinction and transformed to the UBV
system. Three times of diminished brightness (at Julian dates of 2,447,287.91,
2,447,316.83, and 2,447,424.63) were suspected of being in either primary or
secondary eclipse. Initially we considered them belonging to the same
(primary) eclipse. Different periods were used to compute phases beginning
with periods around 29 days, the time elapsed between the first two minima in
the data. Periods in this vicinity failed to bring all three points together
in phase. Then, considering the data contained points from both the primary
and the secondary eclipse, periods around twice the suspected 29-day value were
explored.

A light curve for HD 181219 with the most likely period, P=55.1d, is shown in
Figure 1. This representation permits eclipses no longer in duration than
about 3.0 days for one eclipse and 3.5 days for the other eclipse. When
computing phases, the deepest point, delta V=1.18m at JD 2,447,287.91, was used
for the preliminary initial epoch. It is evident from the light curve that
this cannot be the exact midpoint. A better approximation would be about a
half day earlier. Thus the best available estimate for the current ephemeris
of this newly discovered eclipsing binary would be

                  JD(hel.)=2,447,287.4+55.1d n.    (1)

Relative to this ephemeris the other eclipse occurs at about phase 0.52. Thus
there must be a slight eccentricity in the orbit.

A photometry project with a more continuous series of observations allowing for
a period around 55 days will be needed to confirm the correctness of our
ephemeris and define the shape of the light curve. Because our photometry is
so scant, we cannot rule out the possibility that the eclipses are deeper than
0.13m nor that the eclipses are complete.


                              [FIGURE 1]

 Figure 1. Light curve of HD 181219. The vertical axis is differential
 magnitude with respect to HR 7379. The horizontal axis is phase computed
 with the ephemeris in equation (1). We are not sure which eclipse is
 primary and which is secondary.


The Vanderbilt 16-inch automatic telescope was obtained with funds from N.S.F.
research grant AST 84-14594 and its continued operation is made possible by
N.A.S.A.  research grant NAG 8-111.


L. RONALD PATTERSON
       and
DOUGLAS S. HALL
Dyer Observatory
Vanderbilt University
Nashville, Tennessee

References:

Fekel, F. C. and Hall, D. S. 1985, I.A.P.P.P. Communication No. 20, 37. [BIBCODE 1985IAPPP..20...37F ]
Hooten, J. T. and Hall, D. S. 1989, in Remote Access Automatic Telescopes,
   edited by D. S. Hayes and R. M. Genet (Mesa: Fairborn Press), in press.