Abstract
We present the analysis of the gravitational microlensing event OGLE-2011-BLG-0251. This anomalous event was observed by several survey and follow-up collaborations conducting microlensing observations towards the Galactic Bulge. Based on detailed modelling of the observed light curve, we find that the lens is composed of two masses with a mass ratio q=1.9 x 10^-3. Thanks to our detection of higher-order effects on the light curve due to the Earth's orbital motion and the finite size of source, we are able to measure the mass and distance to the lens unambiguously. We find that the lens is made up of a planet of mass 0.53 +- 0.21,M_Jup orbiting an M dwarf host star with a mass of 0.26 +- 0.11 M_Sun. The planetary system is located at a distance of 2.57 +- 0.61 kpc towards the Galactic Centre. The projected separation of the planet from its host star is d=1.408 +- 0.019, in units of the Einstein radius, which corresponds to 2.72 +- 0.75 AU in physical units. We also identified a competitive model with similar planet and host star masses, but with a smaller orbital radius of 1.50 +- 0.50 AU. The planet is therefore located beyond the snow line of its host star, which we estimate to be around 1-1.5 AU.
Highlights
Gravitational microlensing is one of the methods that allow us to probe the populations of extrasolar planets in the Milky Way, and has led to the discoveries of 16 planets1, several of which could not have been detected with other techniques (e.g. Beaulieu et al 2006; Gaudi et al 2008; Muraki et al 2011)
In this paper we present an analysis of microlensing event Optical Gravitational Lens Experiment (OGLE)-2011-BLG-0251, an anomalous event discovered during the 2011 season by the OGLE collaboration and observed intensively by follow-up teams
Our coverage and analysis of OGLE-2011-BLG-0251 has allowed us to locate and constrain a best-fit binary-lens model corresponding to an M star being orbited by a giant planet
Summary
Gravitational microlensing is one of the methods that allow us to probe the populations of extrasolar planets in the Milky Way, and has led to the discoveries of 16 planets, several of which could not have been detected with other techniques (e.g. Beaulieu et al 2006; Gaudi et al 2008; Muraki et al 2011). Gravitational microlensing is one of the methods that allow us to probe the populations of extrasolar planets in the Milky Way, and has led to the discoveries of 16 planets, several of which could not have been detected with other techniques Microlensing events can reveal cool, low-mass planets that are difficult to detect with other methods. This method presents several observational and technical challenges, it has recently led to several significant scientific results. Our modelling approach and results are outlined in Sect. 4; we translate this into physical parameters of the lens system in Sect. 5 and discuss the properties of the planetary system we infer
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