A Suggested Search for Partial Eclipses in the Nearby Binary Star Gliese 793.1 (HD 195987) (poster abstract)

Volume 38 number 1 (2010)

Frederick R. West

520 Diller Road, Hanover, PA 17331

Abstract

Osborn and Hershey (1999, Pub. Astron. Soc. Pacific, 111, 566) have recently published orbital elements and their astrometric parameters found from spectroscopy and HIPPARCOS astrometry for the nearby two-line spectroscopic binary (SB2) star HD 195987 (Gliese 793.1), and have also recommended a more complete study of this binary star. The two solar-type stars of Gliese 793.1 have a 57.324 day period of revolution and a 48,000,000 km mean separation in a fairly eccentric (e=0.306) orbit whose plane almost contains our line of sight to the star (its orbital plane has the inclination i=89.5 ±8.4 to the plane of the sky). The component stars A and B have estimated radii of 615,000 km and 560,000 km, respectively. The minimum projected separation of their centers on the plane of the sky found from the above orbital elements is about 420,000 km, which indicates that partial eclipses of the stars may occur, since this separation is less than the radius of either star. The intervals of Julian dates when possible eclipses seem most likely from the orbital elements are predicted for the last half of 1999, 2000, and 2002. The detection of such eclipses and precise photometry of their light curves could improve the accuracy of the orbital elements of Gliese 793.1 and could give better values for the radii and photospheric temperatures of its components A and B. More precise photometry could also be done on Gliese 793.1 to try to detect transits of its component stars by extrasolar planets orbiting them, using the matched filter method suggested by Jenkins, Doyle, and Cullers (1996, Icarus, 119, 244) for detecting transits of the stars of Gliese 630.1A (CM Draconis) by planets orbiting them.