THE ORBIT AND MASS OF PROCYON

Abstract

ABSTRACT We have determined the orbit and parallax of the Procyon system (F5 IV-V primary and white dwarf secondary) using conventional absolute radial velocities, precise relative radial velocities determined with the hydrogen flouride (HF) absorption-cell technique, and astrometric and visual observations. Our least-squares analysis confirms and strengthens Strand's previous analysis based on more limited material. We derive an absolute parallax of piabs=0.2899 ± 0.0074 arcsec. Our parallax result is in excellent agreement with other parallax investigations based on independent material. If we adopt the latest USNO parallax of piabs=0.2864 ± 0.0023 arcsec, then from our orbital paramters we derive MA=1.751 ± 0.051 solar mass, and MB=0.622 ± 0.017 solar mass. For the derived mass of Procyon A (which is consistent with previous results), it has long been known that the luminosity predicted by stellar interior theory is approximately a factor of two larger than the luminosity derived from observations. The errors in this observed luminosity and the above formal standard errors (i.e., our best estimates of the statistical random errors) in our derived mass are too small to explain this discrepancy. If the observed separation of the binary components has been systematically overestimated by approximately 0.2 arcsec, then the derived mass would be reduced, thus resolving the discrepancy. However, the excellent consistency of the separations measured by Aitken and Barnard for a number of years at different sites argues against this interpretation. The stellar interior theory of Procyon A may need substantial revision.