Astrophysics, abstract
astro-ph/0604502

From: Saskia Hekker [view email]

Date: Tue, 25 Apr 2006 11:20:52 GMT (97kb)

Precise radial velocities of giant stars: I. Stable stars

Authors: S. Hekker, S. Reffert, A. Quirrenbach, D.S. Mitchell, D.A. Fischer, G.W. Marcy, R.P. Butler

Comments: 8 pages, 4 figures, 2 tables, accepted for publication in A&A

Context: Future astrometric missions such as SIM PlanetQuest need very stable reference stars. K giants have large luminosities, which place them at large distances and thus the jitter of their photocenters by companions is relatively small. Therefore K giants would be best suited as references. To confirm this observationally a radial velocity survey is performed to quantify the level of intrinsic variability in K giants.

Aims: From this radial velocity survey we present 34 K giants with an observed standard deviation of the radial velocity of less than 20 m/s. These stars are considered ``stable'' and can be used as radial velocity standards.

Methods: The radial velocity survey contains 179 K giants. All K giants have a declination between -30 and +65 degrees and visual magnitude of 3-6 mag. The Coude Auxiliary Telescope (CAT) at UCO/Lick Observatory is used to obtain radial velocities with an accuracy of 5-8 m/s. The number of epochs for the 34 stable stars ranges from 11 to 28 with a total timespan of the observations between 1800 and a little over 2200 days.

Results: The observational results of the 34 ``stable'' stars are shown together with a discussion about their position in the M_{V} vs. B-V diagram and some conclusions concerning the radial velocity variability of K giants. These results are in agreement with the theoretical predictions. K giants in a certain range of the M_{V} vs. B-V diagram are suitable reference stars.

http://arxiv.org/abs/astro-ph/0604502