Measurement of the Free-Floating Planet Mass Function with Simultaneous Euclid and WFIRST Microlensing Parallax Observations

TL;DR

This paper discusses how simultaneous observations by Euclid and WFIRST can enable microlensing parallax measurements to determine the masses of free-floating planets, enhancing our understanding of planetary system dynamics.

Contribution

It proposes a method using Euclid and WFIRST to measure free-floating planet masses via microlensing parallax, with a feasible observing strategy.

Findings

Hundreds of parallax measurements can be obtained with modest observing time.

Euclid's precursor observations can improve mass measurements of bound planets.

The approach enhances the scientific return of WFIRST and Euclid missions.

Abstract

Free-floating planets are the remnants of violent dynamical rearrangements of planetary systems. It is possible that even our own solar system ejected a large planet early in its evolution. WFIRST will have the ability to detect free-floating planets over a wide range of masses, but it will not be able to directly measure their masses. Microlensing parallax observations can be used to measure the masses of isolated objects, including free-floating planets, by observing their microlensing events from two locations. The intra-L2 separation between WFIRST and Euclid is large enough to enable microlensing parallax measurements, especially given the exquisite photometric precision that both spacecraft are capable of over wide fields. In this white paper we describe how a modest investment of observing time could yield hundreds of parallax measurements for WFIRST's bound and free-floating planets. We also describe how a short observing campaign of precursor observations by Euclid can improve WFIRST's bound planet and host star mass measurements.