Astronomy & Astrophysics

A&A 483, 317-324 (2008)
DOI: 10.1051/0004-6361:20077449

Limits on additional planetary companions to OGLE 2005-BLG-390L

D. Kubas¹, A. Cassan², M. Dominik³, D. P. Bennett⁴, J. Wambsganss², S. Brillant¹, J. P. Beaulieu⁵, M. D. Albrow⁶, V. Batista⁵, M. Bode⁷, D. M. Bramich⁸, M. Burgdorf⁷, J. A. R. Caldwell⁹, H. Calitz¹⁰, K. H. Cook¹¹, Ch. Coutures¹², S. Dieters¹³, D. Dominis Prester¹⁴, J. Donatowicz¹⁵, P. Fouqué¹⁶, J. Greenhill¹³, K. Hill¹³, M. Hoffman¹⁰, K. Horne³, U. G. Jørgensen¹⁷, N. Kains³, S. Kane¹⁸, J. B. Marquette⁴, R. Martin¹⁹, P. Meintjes¹⁰, J. Menzies²⁰, K. R. Pollard¹⁹, K. C. Sahu²¹, C. Snodgrass¹, I. Steele⁷, Y. Tsapras²², C. Vinter¹⁷, A. Williams¹⁹, K. Woller¹⁷, and M. Zub (The PLANET/RoboNet Collaboration)²

¹ European Southern Observatory, Casilla 19001, Vitacura 19, Santiago, Chile
e-mail: dkubas@eso.org
² Astronomisches Rechen-Institut, Zentrum für Astronomie, Heidelberg University, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
³ SUPA, University of St Andrews, School of Physics & Astronomy, North Haugh, St Andrews, KY16 9SS, UK
⁴ University of Notre Dame, Department of Physics, 225 Nieuwland Science Hall Notre Dame, USA
⁵ Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
⁶ University of Canterbury, Department of Physics & Astronomy, Private Bag 4800, Christchurch, New Zealand
⁷ Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD, UK
⁸ Isaac Newton Group, Apartado de Correos 321, 38700 Santa Cruz de La Palma, Spain
⁹ McDonald Observatory, 16120 St Hwy Spur 78, Fort Davis, TX 79734, USA
¹⁰ Dept. of Physics / Boyden Observatory, University of the Free State, Bloemfontein 9300, South Africa
¹¹ Lawrence Livermore National Laboratory, IGPP, PO Box 808, Livermore, CA 94551, USA
¹² DSM/DAPNIA, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
¹³ University of Tasmania, School of Maths and Physics, Private bag 37, GPO Hobart, Tasmania 7001, Australia
¹⁴ Physics department, Faculty of Arts and Sciences, University of Rijeka, 51000 Rijeka, Croatia
¹⁵ Technical University of Vienna, Dept. of Computing, Wiedner Hauptstrasse 10, Vienna, Austria
¹⁶ Observatoire Midi-Pyrénées, UMR 5572, 14 avenue Edouard Belin, 31400 Toulouse, France
¹⁷ Niels Bohr Institute, Astronomical Observatory, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
¹⁸ Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055, USA
¹⁹ Perth Observatory, Walnut Road, Bickley, Perth 6076, Australia
²⁰ South African Astronomical Observatory, PO Box 9 Observatory 7935, South Africa
²¹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
²² Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK

(Received 9 March 2007 / Accepted 18 February 2008)

Abstract
Aims. We investigate constraints on additional planets orbiting the distant M-dwarf star OGLE 2005-BLG-390L, around which photometric microlensing data has 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 also 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.
Methods. We 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.
Results. We find that more than $50\%$ of potential planets with a mass in excess of 1 M_</I>J between 1.1 and 2.3 AU around OGLE 2005-BLG-390L would have revealed their existence, whereas for gas giants above 3 M_</I>J 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 of around $2{-}5\%$ . In agreement with current planet formation theories, this quantitatively supports the prediction that sub-Neptune mass planets are common around low-mass stars.