An Isolated Microlens Observed from K2, Spitzer and Earth

TL;DR

This paper reports on a microlensing event observed from K2, Spitzer, and Earth, demonstrating how multi-satellite observations can effectively determine the properties of a lens, specifically an extremely low-mass star in the Galactic bulge.

Contribution

It presents the first microlensing event with signals from three well-separated locations, showcasing the power of multi-satellite observations in resolving lens property degeneracies.

Findings

Degeneracy in lens mass and distance was broken with Spitzer data.

The lens is identified as an extremely low-mass star in the Galactic bulge.

First microlensing event observed from three well-separated locations.

Abstract

We present the result of microlensing event MOA-2016-BLG-290, which received observations from the two-wheel Kepler (K2), Spitzer, as well as ground-based observatories. A joint analysis of data from K2 and the ground leads to two degenerate solutions of the lens mass and distance. This degeneracy is effectively broken once the (partial) Spitzer light curve is included. Altogether, the lens is found to be an extremely low-mass star located in the Galactic bulge. MOA-2016-BLG-290 is the first microlensing event for which we have signals from three well-separated ($\sim1$ AU) locations. It demonstrates the power of two-satellite microlensing experiment in reducing the ambiguity of lens properties, as pointed out independently by S. Refsdal and A. Gould several decades ago.