COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2243

                                     Konkoly Observatory
                                     Budapest
                                     1982 December 8

                                     HU ISSN 0374-0676




             HR 7578: A POSSIBLE LATE-TYPE ECLIPSING
             BINARY AND/OR A BY DRACONIS VARIABLE



High dispersion spectroscopic observations obtained at the Erwin W.
Fick Observatory, Iowa State University and McDonald Observatory, University
of Texas have shown that HR 7578 = HD 188088 is a bright, V=6.16, double-lined
K2-3 V binary with a period of 46.8 days and an eccentricity of 0.69. The
minimum masses of the components are 0.85 +/- 0.03 MSun each, suggesting that the
inclination of the system may be high enough for eclipses to occur despite the
relatively long period and presumed small radii of the stars.
Because there are very few eclipsing binaries of solar type or later, a
search for such eclipses is important. Since the declination of this object is
-24deg, it is best observed from the southern hemisphere. The ephemerides for
possible eclipses are

              2444147.591 + 46.817E

for a possible eclipse near apastron and

              2444158.880 + 46.817E

for a possible eclipse near periastron.
   Because of the large eccentricity, an eclipse near periastron is more likely
to occur and could last up to 10 hours. A total eclipse near apastron would last
about 54 hours. Spectroscopic observations obtained near times of possible
eclipse minima show little, if any, change in line strengths, implying that the
possible eclipses are at best partial. During 1983, the best opportunity to
observe a possible eclipse near periastron occurs in mid-May.




    Spectroscopic observations indicate that the components have v sin i's
of 5 - 8 km s^-1 each. Such rotational velocities (Bopp, Noah, and Klimke 1980)
suggest that the system may be a BY Draconis variable. Thus, low amplitude,
quasi-sinusoidal light variations with a period of 5 - 8 days may be detected.
A full discussion of this system will appear in a forthcoming volume of the
Astrophysical Journal.





              FRANCIS C. FEKEL, JR.

              Goddard Space Flight Center
              Laboratory for Astronomy and
              Solar Physics
              Code 685
              Greenbelt, Maryland 20771

              W. I. BEAVERS

              Erwin W. Fick Observatory
              Iowa State University
              Ames, Iowa 50010




Reference:

Bopp, B. W., Noah, P. V., and Klimke, A. 1980, A.J. 85, 1386. [BIBCODE 1980AJ.....85.1386B ]