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

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 binary-lens solutions by a factor of ∼2, demonstrating the power of high-angular-resolution follow-up imaging for events with sparse light-curve coverage. Following Bennett et al., we apply constraints from the high-resolution imaging on the light-curve modeling to find host star and planet masses of M _host = 0.28 ± 0.04 M _☉ and ${m}_{p}={12.49}_{-8.03}^{+65.47}\,{M}_{\oplus }$ at a distance from Earth of D _L = 2.16 ± 0.30 kpc. This work illustrates the necessity for the Nancy Grace Roman Galactic Exoplanet Survey to use its own high-resolution imaging to inform light-curve modeling for microlensing planets that the mission discovers.

Keywords

• Exoplanets
• Gravitational microlensing
• Adaptive optics
• High-resolution microlensing event imaging
• Observational astronomy
• Astronomy data modeling