Estimating Finite Source Effects in Microlensing Events due to Free-Floating Planets with the Euclid Survey

TL;DR

This paper explores the potential of the Euclid survey to detect finite source effects in microlensing events caused by free-floating planets, enabling better understanding of their properties and the stars in the Galactic bulge.

Contribution

It demonstrates the feasibility of detecting finite source effects in FFP microlensing events with Euclid, and assesses the potential to measure lens parameters and study stellar atmospheres.

Findings

Finite source effect detection efficiency is 20-40%.

Euclid can measure the angular Einstein radius for many events.

Observations can provide insights into stellar atmospheres.

Abstract

In recent years free-loating planets (FFPs) have drawn a great interest among astrophysicists. Gravitational microlensing is a unique and exclusive method for their investigation which may allow obtaining precious information about their mass and spatial distribution. The planned Euclid space-based observatory will be able to detect a substantial number of microlensing events caused by FFPs towards the Galactic bulge. Making use of a synthetic population algorithm, we investigate the possibility of detecting finite source effects in simulated microlensing events due to FFPs. We find a significant efficiency for finite source effect detection that turns out to be between 20% and 40% for a FFP power law mass function index in the range [0.9, 1.6]. For many of such events it will also be possible to measure the angular Einstein radius and therefore constrain the lens physical parameters. These kinds of observations will also offer a unique possibility to investigate the photosphere and atmosphere of Galactic bulge stars.