Fundamental photon noise limit to radial velocity measurements

Abstract

In the past 5 years, improvements in radial velocity measurements have led to discovery of extra-solar planets and progress in asteroseismology programs. Doppler measurements with high precision is close to the limit given by photon noise. In this paper the methodology to compute the fundamental limit of radial velocity measurement given by photon noise is presented and illustrated with a representative sample of synthetic solar-type stellar spectra. Stellar rotational broadening, instrumental spectral range as well as spectral resolution influences are also considered. This study is applied to two dedicated spectrographs in order to help the optimization of radial velocity programs. Current methods of Doppler calculation are discussed and compared.