Detectability of Extrasolar Planets in Radial Velocity Surveys

Abstract

Radial velocity surveys are beginning to reach the time baselines required to detect Jupiter analogs, as well as sub-Saturn mass planets in close orbits. Therefore it is important to understand the sensitivity of these surveys at long periods and low amplitudes. In this paper, I derive analytic expressions for the detectability of planets at both short and long periods, for circular and eccentric orbits. I suggest an extension of the Lomb-Scargle periodogram for Keplerian orbits, and describe how to estimate the false alarm probability associated with a Keplerian fit. Using this to investigate the detectability of eccentric orbits shows that there are significant selection effects against eccentric orbits for e>0.6, and the small number of highly eccentric planets discovered so far may reflect this. Finally, I present a Bayesian approach to the periodogram, which emphasises the equivalence of least squares and periodogram techniques.