A giant planet beyond the snow line in microlensing event OGLE-2011-BLG-0251

Abstract

Aims. 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. Methods. 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 × 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. Results. We find that the lens is made up of a planet of mass 0.53 ± 0.21 M J orbiting an M dwarf host star with a mass of 0.26 ± 0.11 M . 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.

Microlensing Searches for Exoplanets

“…Hundreds of millions of stars are now monitored as often as every 10-30 min in the direction of the Galactic bulge, and this substantially improved survey sensitivity to planetary signals in the light curve. Follow-up observations from different longitudes are still useful for independently confirming the signals, as well as providing light curve coverage when the Galactic bulge is not visible from the survey sites, either due to inclement weather or during daytime [143][144][145][146]. Survey efforts were greatly augmented in 2016, when the Korea Microlensing Telescope Network (KMTNet) commenced full operations with its three 1.6 m survey telescopes in Chile, Australia and South Africa, which were deployed and commissioned during 2015 [38,147,148].…”

New variable stars towards the Galactic Bulge. I. The bright regime★†

“…Kains et al 2015Kains et al , 2013bKains et al , 2012bFiguera Jaimes et al 2013;Bramich et al 2011) and the Galactic Bulge (e.g. Kains et al 2013a). Each VIMOS quadrant was reduced separately with its own reference image (see Fig.…”

“…We carried out searches for variable stars by using a number of independent methods. We first used the variability index S R , as defined by Kains et al (2013aKains et al ( , 2015; briefly, this quantifies the improvement in the phased light curve using the best-fit period compared to a random period. This is done by measuring the respective string lengths of the phased light curves, i.e.…”

Theoretical estimations of future polarization observations for exoplanery searches with gravitational microlensing

“…A list of exoplanets detected with microlensing searches toward the Galactic bulge is given in Table 1 (see, [3,26,27,28,29,30,31,32,33,34,35,36,37]). For some planetary systems two probable regions for the planet-to-star distance are given due to the planet and star-lens parameter degeneracy [28,38], see rows 9, 14, 17 in Table 1.…”

“…For some planetary systems two probable regions for the planet-to-star distance are given due to the planet and star-lens parameter degeneracy [28,38], see rows 9, 14, 17 in Table 1. Reports about these discoveries were published in [11,27,29,30,31,32,33,34,35,36,37,39,40,41,42,44,45,46,47,48,49,50]. In these searches we have a continuous transition from massive exoplanets to brown dwarfs, since an analysis of the anomalous microlensing event, MOA-2010-BLG-073 has been done [51], where the primary of the lens is an M-dwarf with M L1 = 0.16 ± 0.03M ⊙ while the companion has M L2 = [54] 11.0 ± 2.0M J 2 , at a perpendicular distance around 1.21 ± 0.16 AU from the host star, so the low mass component of the system is near a boundary between planets and brown dwarfs.…”