Astrometric study of Barnard's star from plates taken with the Sproul 61-cm refractor

Abstract

Twenty-five consecutive years of photographic observations of Barnard’s star show deviations from uniform proper motion and secular acceleration which can be represented by Keplerian motion with a period of 24 yr and semi-axis major of '(0245=b'(002 (p.e.). Assuming a value of 0.150 for the mass of Barnard’s star, the mass of the companion proves to be 0.00150, or 1.6 times the mass of Jupiter.