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Hubble Space Telescope Astrometry of the Procyon SystemThe nearby star Procyon is a visual binary containing the F5 IV-V subgiant Procyon A, orbited in a 40.84-year period by the faint DQZ white dwarf (WD) 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 plus or minus 0.012M and 0.592 plus or minus 0.006M 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 approximately 2.7 Gyr. Procyon B's location in the H-R diagram is in excellent agreement with theoretical cooling tracks for WDs 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 1.9-2.2M, depending on its amount of core overshoot. Several astrophysical puzzles remain. In the progenitor system, the stars at periastron were separated by only approximately 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 (approximately 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.
Document ID
20160002444
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Bond, Howard E.
(Pennsylvania State Univ. University Park, PA, United States)
Gilliland, Ronald L.
(Space Telescope Science Inst. Huntsville, AL, United States)
Schaefer, Gail H.
(Georgia State Univ. Atlanta, GA, United States)
Demarque, Pierre
(Yale Univ. New Haven, CT, United States)
Girard, Terrence M.
(Yale Univ. New Haven, CT, United States)
Holberg, Jay B.
(Arizona Univ. Tucson, AZ, United States)
Gudehus, Donald
(Georgia State Univ. Atlanta, GA, United States)
Mason, Brian D.
(Naval Observatory Washington, DC, United States)
Kozhurina-Platais, Vera
(Space Telescope Science Inst. Baltimore, MD, United States)
Burleigh, Matthew R.
(Leicester Univ. United Kingdom)
Date Acquired
February 29, 2016
Publication Date
November 10, 2015
Publication Information
Publication: The Astrophysical Journal
Volume: 813
Issue: 2
ISSN: 1538-4357
Subject Category
Astronomy
Report/Patent Number
AD-A626355
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other
Keywords
PROCYON
ASTROMETRY

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