Spitzer vs Keck: Comparing mass measurement methods for OGLE-2016-BLG-1195

Gravitational microlensing is just one of the many ways that new planets can be detected. It is set apart, however, by its unique sensitivity to low-mass wide-orbit planets. The method of microlensing, although efficient in measuring planet-host mass ratios, does not have the capability of precisely measuring masses. These precise mass measurements are crucial for exoplanet demographic studies and formation theories. The mass of a microlensed system can be derived from parallax constraints or from directly measuring the flux of the host star. For the event OGLE-2016-BLG-1195, both methods have been used but have yielded different results. A microlensing parallax from the Spitzer space telescope showed the system to be an ultracool dwarf orbited by an Earth-mass planet, with the results published in Shvartzvald et al 2017. However, high-resolution follow-up observations conducted with the Keck telescopes, indicate that the system could be a Super-Earth orbiting an M-dwarf star.

In this talk I will compare the Spitzer parallax and high-resolution follow-up observations as methods to accurately determine the mass of a host star and its planet, within the context of the microlensing event OGLE-2016-BLG-1195.