We present adaptive optics imaging from the NIRC2 instrument on the Keck-2 telescope that resolves the exoplanet host ( and lens ) star as it separates from the brighter source star .
These observations yield the K -band brightness of the lens and planetary host star , as well as the lens-source relative proper motion , { \mbox { \boldmath$ \bf \mu$ } } _ { rel,H } .
in the heliocentric reference frame .
The { \mbox { \boldmath$ \bf \mu$ } } _ { rel,H } measurement allows determination of the microlensing parallax vector , { \mbox { \boldmath$ \bf \pi$ } _ { E } } , which had only a single component determined by the microlensing light curve .
The combined measurements of { \mbox { \boldmath$ \bf \mu$ } } _ { rel,H } and K _ { L } provide the masses of the host stat , M _ { host } = 0.426 \pm 0.037 M _ { \odot } , and planet , m _ { p } = 3.27 \pm 0.32 M _ { Jupiter } with a projected separation of 3.4 \pm 0.5 AU .
This confirms the tentative conclusion of a previous paper ( 27 ) that this super-Jupiter mass planet , OGLE-2005-BLG-071Lb , orbits an M-dwarf .
Such planets are predicted to be rare by the core accretion theory and have been difficult to find with other methods , but there are two such planets with firm mass measurements from microlensing , and an additional 11 planetary microlens events with host mass estimates < 0.5 M _ { \odot } and planet mass estimates > 2 Jupiter masses that could be confirmed by high angular follow-up observations .
We also point out that OGLE-2005-BLG-071L has separated far enough from its host star that it should be possible to measure the host star metalicity with spectra from a high angular resolution telescope such as Keck , the VLT , the Hubble Space Telescope or the James Webb Space Telescope .