We report the discovery of a Jupiter-mass planet orbiting an M-dwarf star that gave rise to the microlensing event OGLE-2011-BLG-0265 .
Such a system is very rare among known planetary systems and thus the discovery is important for theoretical studies of planetary formation and evolution .
High-cadence temporal coverage of the planetary signal combined with extended observations throughout the event allows us to accurately model the observed light curve .
The final microlensing solution remains , however , degenerate yielding two possible configurations of the planet and the host star .
In the case of the preferred solution , the mass of the planet is M _ { p } = 0.9 \pm 0.3 M _ { J } , and the planet is orbiting a star with a mass M = 0.22 \pm 0.06 M _ { \odot } .
The second possible configuration ( 2 \sigma away ) consists of a planet with M _ { p } = 0.6 \pm 0.3 M _ { J } and host star with M = 0.14 \pm 0.06 M _ { \odot } .
The system is located in the Galactic disk 3 – 4 kpc towards the Galactic bulge .
In both cases , with an orbit size of 1.5 – 2.0 AU , the planet is a “ cold Jupiter ” – located well beyond the “ snow line ” of the host star .
Currently available data make the secure selection of the correct solution difficult , but there are prospects for lifting the degeneracy with additional follow-up observations in the future , when the lens and source star separate .