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Astrometric versus Spectroscopic Radial Velocities1

Published online by Cambridge University Press:  12 April 2016

Dainis Dravins ,
Dag Gullberg ,
Lennart Lindegren  and
Søren Madsen
Dainis Dravins
Affiliation:
Lund Observatory, Box 43, SE-22100 Lund, Sweden
Dag Gullberg
Affiliation:
Lund Observatory, Box 43, SE-22100 Lund, Sweden
Lennart Lindegren
Affiliation:
Lund Observatory, Box 43, SE-22100 Lund, Sweden
Søren Madsen
Affiliation:
Lund Observatory, Box 43, SE-22100 Lund, Sweden

Abstract

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The apparent radial velocity of a star, as deduced from wavelength shifts, comprises not merely its true velocity, but also components arising from dynamics in the star’s atmosphere, gravitational redshift, and other effects. For the Sun, such phenomena can be segregated since the relative Sun-Earth motion is known from planetary system dynamics. This is now becoming possible also for other stars, whose true radial motions are determined through space astrometry. A study of the differences between accurate astrometric velocities (from Hipparcos), and precise spectroscopic values (from ELODIE) is in progress. Data for cool stars in the Hyades indicate a tendency of relative blueshifts among earlier main-sequence F-type stars, and in giants. This is theoretically expected: an increased convective blueshift due to the more vigorous convection in F-stars, and a decreased gravitational redshift in giants.

Type
Part 2. Fundamental Concepts and Techniques
Information
International Astronomical Union Colloquium , Volume 170: Precise Stellar Radial Velocities , 1999 , pp. 41 - 47
Copyright
Copyright © Astronomical Society of the Pacific 1999

Footnotes

1

Based on data from the ESA Hipparcos astrometry satellite, and on observations collected at Observatoire de Haute-Provence.

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