Astrometric search for a stellar companion to the Sun

Description/Abstract

A companion star within 0.8 pc of the Sun has been postulated to explain a possible 26-Myr periodicity in mass extinctions of species on the Earth. Such a star would already be catalogued in the Yale Bright Star catalogue unless it is fainter than m/sub v/ = 6.5; this limits the possible stellar types for an unseen companion to red dwarfs, brown dwarfs, or compact objects. Red dwarfs account for about 75% of these possible stars. An astrometric search is described here for a nearby red dwarf companion with a six-month peak-to-peak parallax of greater than or equal to2.5 arcseconds. The parallax of 2770 candidate faint red stars selected from the Dearborn Observatory catalogue are being studied. An automated 30-inch telescope and CCD camera system collect digitized images of the candidate stars, along with a 14' X 16' surrounding field of background stars. Second-epoch images, taken a few months later, are registered to the first-epoch images using the background stars as fiducials. The search procedure with observations of 41 stars, and have shown that none of these is a nearby star has been demonstrated.