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Title: Hubble Space Telescope Astrometry of the Procyon System
Authors: Bond, H. E.
Gilliland, R. L.
Schaefer, G. H.
Demarque, P.
Girard, T. M.
Holberg, J. B.
Gudehus, D.
Mason, B. D.
Kozhurina-Platais, V.
Burleigh, Matthew R.
Barstow, Martin A.
Nelan, E. P.
First Published: 4-Nov-2015
Publisher: American Astronomical Society
Citation: Astrophysical Journal , 2015, 813(2), p 106
Abstract: The nearby star Procyon is a visual binary containing the F5 IV-V subgiant Procyon A, orbited in a 40.84 yr period by the faint DQZ white dwarf Procyon B. Using images obtained over two decades with the Hubble Space Telescope, and historical measurements back to the 19th century, we have determined precise orbital elements. Combined with measurements of the parallax and the motion of the A component, these elements yield dynamical masses of 1.478 +/- 0.012 Msun and 0.592 +/- 0.006 Msun for A and B, respectively. The mass of Procyon A agrees well with theoretical predictions based on asteroseismology and its temperature and luminosity. Use of a standard core-overshoot model agrees best for a surprisingly high amount of core overshoot. Under these modeling assumptions, Procyon A's age is ~2.7 Gyr. Procyon B's location in the H-R diagram is in excellent agreement with theoretical cooling tracks for white dwarfs of its dynamical mass. Its position in the mass-radius plane is also consistent with theory, assuming a carbon-oxygen core and a helium-dominated atmosphere. Its progenitor's mass was 1.9-2.2 Msun, depending on its amount of core overshoot. Several astrophysical puzzles remain. In the progenitor system, the stars at periastron were separated by only ~5 AU, which might have led to tidal interactions and even mass transfer; yet there is no direct evidence that these have occurred. Moreover the orbital eccentricity has remained high (~0.40). The mass of Procyon B is somewhat lower than anticipated from the initial-to-final-mass relation seen in open clusters. The presence of heavy elements in its atmosphere requires ongoing accretion, but the place of origin is uncertain.
DOI Link: 10.1088/0004-637X/813/2/106
ISSN: 0004-637X
eISSN: 1538-4357
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2015 AAS. All rights reserved.Deposited with reference to the publisher’s open access archiving policy, available at
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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