Asteroids as radial velocity and resolving power standards for medium and high resolution spectroscopy ^*

¹ University of Ljubljana, Faculty of Mathematics and Physics, Department of Physics, Jadranska 19, 1000 Ljubljana, Slovenia e-mail: tomaz.zwitter@funf.uni-Lj.si
² Observatoire de la Côte d'Azur, Cassiopée, CNRS UMR 5202, BP 4229, 06304 Nice Cedex 4, France
³ Observatoire de Paris, GEPI, 5 place Jules Janssen, 92195 Meudon, France

Received: 29 June 2005
Accepted: 30 August 2006

Abstract

Echelle spectra of 10 bright asteroids are presented and compared against an observed twilight spectrum and a computed Solar spectrum. Spectra covering a 2130 Å  spectral range centered on  Å are of high resolving power and high signal to noise ratio. We compare detailed properties of spectral lines and not albedo variations. It is shown that the normalized Solar and asteroid spectra are identical except for radial velocity (RV) shifts which can be predicted at accuracy level of 1 m s^-1. So asteroids are proposed as new and extremely accurate radial velocity standards. Predicted and measured RVs of observed asteroids match within the limits of accuracy of the instrument. There are numerous absorption lines in the reflected Solar spectrum. This allows a direct mapping of the resolving power of a spectrograph between and along echelle spectral orders. Thus asteroid spectra can be used to test the wavelength calibration and resolving power of spectrographs on the ground as well as in space, including the Gaia mission of ESA. All spectra are given in electronic form.