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The mass of Procyon A as determined from stellar evolution theory does not agree with the value derived astrometrically. The astrometric orbit of the Procyon system is based on photographic plate measures performed in the 1950's, without the aid of modern plate-measuring equipment. Here we present preliminary results of a redetermination of the astrometric orbit based on Yale PDS microdensitometer measures of a large number of plates gathered from the plate collections of several observatories. The available plate material from McCormick, Sproul, US Naval, Van Vleck, Yale, and Yerkes Observatories spans an epoch range of 1912-1990, roughly twice the 40-year orbital period of the system. In total, over 1000 exposures on over 300 plates will be measured. The majority of the plate measurements have been completed. Preliminary orbital parameters and trigonometric parallax based on the combined plate measures are presented.
This research was supported in part by funds from the National Science Foundation through the AAS/REU program.
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