We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb , the second planet discovered by microlensing and the first in a high-magnification event .
These include photometric and astrometric measurements from Hubble Space Telescope , as well as constraints from higher order effects extracted from the ground-based light curve , such as microlens parallax , planetary orbital motion and finite-source effects .
Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is an M dwarf in the foreground disk with mass M = 0.46 \pm 0.04 M _ { \odot } , distance D _ { l } = 3.2 \pm 0.4 kpc , and thick-disk kinematics v _ { LSR } \sim 103 km s ^ { -1 } .
From the best-fit model , the planet has mass M _ { p } = 3.8 \pm 0.4 M _ { Jupiter } , lies at a projected separation r _ { \perp } = 3.6 \pm 0.2 AU from its host and so has an equilibrium temperature of T \sim 55 K , i.e. , similar to Neptune .
A degenerate model less favored by \Delta { \chi ^ { 2 } } = 2.1 ( or 2.2 , depending on the sign of the impact parameter ) gives similar planetary mass M _ { p } = 3.4 \pm 0.4 M _ { Jupiter } with a smaller projected separation , r _ { \perp } = 2.1 \pm 0.1 AU , and higher equilibrium temperature T \sim 71 K. These results from the primary analysis suggest that OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that is hosted by an M dwarf .
However , the formation of such high-mass planetary companions in the outer regions of M-dwarf planetary systems is predicted to be unlikely within the core-accretion scenario .
There are a number of caveats to this primary analysis , which assumes ( based on real but limited evidence ) that the unlensed light coincident with the source is actually due to the lens , that is , the planetary host .
However , these caveats could mostly be resolved by a single astrometric measurement a few years after the event .