* Astronomy

Title: Limits on further planetary companions to OGLE-2005-BLG-390L
Authors: D. Kubas, A. Cassan, M. Dominik, D. Bennett, et al

We investigate constraints on further planets orbiting the distant M-dwarf star OGLE-2005-BLG-390L, around which photometric microlensing data revealed the existence of the sub-Neptune-mass planet OGLE-2005-BLG-390Lb. We specifically aim to study potential Jovian companions and compare our findings with predictions from core-accretion and disc-instability models of planet formation. We further obtain an estimate of the detection probability for sub-Neptune mass planets similar to OGLE-2005-BLG-390Lb using a simplified simulation of a microlensing experiment. We extend the work of Gaudi and Sackett (2000) to compute the efficiency of our photometric data for detecting additional planets around OGLE-2005-BLG-390L as a function of the microlensing model parameters and convert it into a function of the orbital axis and planet mass by means of an adopted model of the Milky Way. We find that more than 50 % of potential planets with a mass in excess of 1 Mj between 1.1 and 2.3 AU around OGLE-2005-BLG-390L would have revealed their existence, whereas for gas giants above 3 Mj in orbits between 1.5 and 2.2 AU the detection efficiency reaches 70 %, however no such companion was observed. Our photometric microlensing data therefore do not contradict the existence of gas giant planets at any separation orbiting OGLE 2005-BLG-390L. Furthermore we find a detection probability for an OGLE-2005-BLG-390Lb-like planet in the lensing zone, given an idealization of the microlensing technique, to be around 1-3 %. In agreement with current planet formation theories this quantitatively supports the prediction that sub-Neptune mass planets are common around low mass stars.

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