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Hubble Space Telescope Astrometry of the Procyon System

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journal contribution
posted on 21.10.2015, 10:38 by H. E. Bond, R. L. Gilliland, G. H. Schaefer, P. Demarque, T. M. Girard, J. B. Holberg, D. Gudehus, B. D. Mason, V. Kozhurina-Platais, Matthew R. Burleigh, Martin A. Barstow, E. P. Nelan
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.

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Citation

Astrophysical Journal , 2015, 813(2), p 106

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

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VoR (Version of Record)

Published in

Astrophysical Journal

Publisher

American Astronomical Society

issn

0004-637X

eissn

1538-4357

Acceptance date

02/10/2015

Copyright date

2015

Available date

04/11/2016

Publisher version

http://iopscience.iop.org/article/10.1088/0004-637X/813/2/106/meta

Language

en

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