Planet formation by nucleated-instability: Comparison with the two first CoRoT runs

Abstract

Aims. We use extended planet formation models to analyse the results the two first runs of CoRoT, namely the initial one (IRa01) and the first long one (LRc01). We compare our calculations to the actual observations and discuss the possible origins of the differences between the two, not only in term of detection rate, but also regarding the magnitude of transiting planets parent stars. Methods. We use a galactic population synthesis model in order to calculate the characteristics of stars in the field-of-view of CoRoT. In a second step, we calculate planet formation models to derive the population of planets expected around these stars. In a third step, using planet evolution models, we calculate the radius of planets predicted by the model and estimate the probability of transit detection and confirmation by radial-velocity follow-up. Results. Our calculations show that the present day CoRoT detection rate, based only on IRa01 and LRc01, is a factor 5 lower than the one predicted assuming all target are dwarf stars. On the other hand, the two detection rates become similar if one assumes some contamination of CoRoT targets by giant stars, or some less optimistic determinations of the noise level, the limiting signal-to-noise ratio and radial velocity follow-up performances. However, in all the cases we have considered, the majority of transits are found around faint stars, in conflict with the actual CoRoT detections.