- Terry, Sean K;
- Beaulieu, Jean-Philippe;
- Bennett, David P;
- Bhattacharya, Aparna;
- Hulberg, Jon;
- Huston, Macy J;
- Koshimoto, Naoki;
- Blackman, Joshua W;
- Bond, Ian A;
- Cole, Andrew A;
- Lu, Jessica R;
- Ranc, Clément;
- Rektsini, Natalia E;
- Vandorou, Aikaterini
We present an analysis of adaptive optics (AO) images from the Keck-I
telescope of the microlensing event MOA-2011-BLG-262. The original discovery
paper by Bennett et al. 2014 reports two distinct possibilities for the lens
system; a nearby gas giant lens with an exomoon companion or a very low mass
star with a planetary companion in the galactic bulge. The $\sim$10 year
baseline between the microlensing event and the Keck follow-up observations
allows us to detect the faint candidate lens host (star) at $K = 22.3$ mag and
confirm the distant lens system interpretation. The combination of the host
star brightness and light curve parameters yields host star and planet masses
of $M_{\rm host} = 0.19 \pm 0.03M_{\odot}$ and $m_p = 28.92 \pm 4.75M_{\oplus}$
at a distance of $D_L = 7.49 \pm 0.91\,$kpc. We perform a multi-epoch cross
reference to \textit{Gaia} DR3 and measure a transverse velocity for the
candidate lens system of $v_L = 541.31 \pm 65.75$ km s$^{-1}$. We conclude this
event consists of the highest velocity exoplanet system detected to date, and
also the lowest mass microlensing host star with a confirmed mass measurement.
The high-velocity nature of the lens system can be definitively confirmed with
an additional epoch of high-resolution imaging at any time now. The methods
outlined in this work demonstrate that the \textit{Roman} Galactic Exoplanet
Survey (RGES) will be able to securely measure low-mass host stars in the
bulge.