HD10647 and the Distribution of Exoplanet Properties with Semi-major Axis


Paper:	HD10647 and the Distribution of Exoplanet Properties with Semi-major Axis
Volume:	321, Extrasolar Planets: Today and Tomorrow
Page:	298
Authors:	Jones, H.R.A.; Butler, R.P.; Tinney, C.G.; Marcy, G.W.; McCarthy, C.; Penny, A.J.; Carter, B.D.
Abstract:	At this conference Mayor et al. announced evidence for an exoplanet in orbit around HD10647. Here we consider the Anglo-Australian Planet Search dataset for HD10647. Our dataset amply covers the claimed orbital period and is of substantially higher precision. We do find weak evidence for an exoplanet with similar parameters to those announced by Mayor et al. However, since the amplitude of proposed planet is rather similar to the jitter velocity we are not in a position to confirm a planetary interpretation. We note that claims of small amplitude planets (<20 ms⁻¹) around active stars are fraught with uncertainty, e.g. ε Eri. We also consider the properties of exoplanets with their orbital semi-major axis. We find that there is a steep rise in the numbers of planets towards larger semimajor axes and do not find strong evidence for a short-period peak of exoplanets. We also find interesting correlations of eccentricity and metallicity with semimajor axis. Eccentricities rise steeply out to semi-major axis values of around 0.2 AU at which point a mean eccentricity of around 0.35 is reached. This mean eccentricity shows a slight decline out to several AU. The trends of metallicity with semi-major axis is less robust. Overall, there maybe a decline in metallicity towards longer semi-major axes arising from the metallicity distribution of low mass exoplanets being more sensitive to semi-major axis.