The Space Interferometry Mission Astrometric Grid Giant Star Survey. I. Stellar Parameters and Radial Velocity Variability Academic Article uri icon


  • We present results from a campaign of multiple-epoch echelle spectroscopy of relatively faint (V=9.5-13.5 mag) red giants observed as potential astrometric grid stars for the Space Interferometry Mission (SIM PlanetQuest). Data are analyzed for 775 stars selected from the Grid Giant Star Survey, spanning a wide range of effective temperatures (t eff), gravities, and metallicities. The spectra are used to determine these stellar parameters and to monitor radial velocity (RV) variability at the 100 m s-1 level. The degree of RV variation measured for 489 stars observed two or more times is explored as a function of the inferred stellar parameters. The percentage of RV-unstable stars is found to be very high - about two-thirds of our sample. It is found that the fraction of RV-stable red giants (at the 100 m s -1 level) is higher among stars with T eff 4500 K, corresponding to the calibration-independent range of infrared colors 0.59 < (J - K s) 0 < 0.73. A higher percentage of RV-stable stars is found if additional constraints of surface gravity and metallicity ranges, 2.3 < log g < 3.2 and -0.5 < [Fe/H] < -0.1, respectively, are applied. Selection of stars based on only photometric values of effective temperature (4300 K < T eff < 4700 K) is a simple and effective way to increase the fraction of RV-stable stars. The optimal selection of RV-stable stars, especially in the case in which the Washington photometry is unavailable, can rely effectively on the 2MASS colors constraint 0.59 < (J - K s) 0 < 0.73. These results have important ramifications for the use of giant stars as astrometric references for the SIM PlanetQuest. 2006. The American Astronomical Society. All rights reserved.

published proceedings

  • The Astronomical Journal

author list (cited authors)

  • Bizyaev, D., Smith, V. V., Arenas, J., Geisler, D., Majewski, S. R., Patterson, R. J., ... Gieren, W.

citation count

  • 13

complete list of authors

  • Bizyaev, Dmitry||Smith, Verne V||Arenas, Jose||Geisler, Doug||Majewski, Steven R||Patterson, Richard J||Cunha, Katia||Del Pardo, Cecilia||Suntzeff, Nicholas B||Gieren, Wolfgang

publication date

  • March 2006