Unveiling MOA-2007-BLG-192: An M Dwarf Hosting a Likely Super-Earth

TL;DR

This study uses high-resolution imaging from Keck and Hubble to precisely characterize the host star and planet of the microlensing event MOA-2007-BLG-192, revealing a likely super-Earth orbiting an M dwarf at 2.16 kpc.

Contribution

It demonstrates how high angular resolution follow-up imaging can resolve degeneracies in microlensing solutions, improving mass and distance estimates of exoplanets.

Findings

Host star mass: 0.28 M_sun

Planet mass: ~12.5 M_earth

Distance: 2.16 kpc

Abstract

We present an analysis of high angular resolution images of the microlensing target MOA-2007-BLG-192 using Keck adaptive optics and the Hubble Space Telescope. The planetary host star is robustly detected as it separates from the background source star in nearly all of the Keck and Hubble data. The amplitude and direction of the lens-source separation allows us to break a degeneracy related to the microlensing parallax and source radius crossing time. Thus, we are able to reduce the number of possible solutions by a factor of ${\sim}2$, demonstrating the power of high angular resolution follow-up imaging for events with sparse light curve coverage. Following Bennett et al. 2023, we apply constraints from the high resolution imaging on the light curve modeling to find host star and planet masses of $M_{\textrm{host}} = 0.28 \pm 0.04M_{\odot}$ and $m_p = 12.49^{+65.47}_{-8.03}M_{\oplus}$ at a distance from Earth of $D_L = 2.16 \pm 0.30\,$kpc. This work illustrates the necessity for the Nancy Grace Roman Galactic Exoplanet Survey (RGES) to use its own high resolution imaging to inform light curve modeling for microlensing planets that the mission discovers.