Interferometric observation of microlensing events

TL;DR

Interferometric observations combined with microlensing data can precisely determine lens properties, with upcoming interferometers expected to significantly increase the number of observable events for detailed analysis.

Contribution

This work introduces a formalism linking interferometric and microlensing observables, defining a new (u,v) plane, and assesses observational strategies and target rates with current and future interferometers.

Findings

A few events are already accessible to current interferometers.

Approximately 6 events per year can be observed with K~10 magnitude limit.

The number of observable events could increase tenfold with a slightly deeper magnitude limit.

Abstract

Interferometric observations of microlensing events have the potential to provide unique constraints on the physical properties of the lensing systems. In this work, we first present a formalism that closely combines interferometric and microlensing observable quantities, which lead us to define an original microlensing (u,v) plane. We run simulations of long-baseline interferometric observations and photometric light curves to decide which observational strategy is required to obtain a precise measurement on vector Einstein radius. We finally perform a detailed analysis of the expected number of targets in the light of new microlensing surveys (2011+) which currently deliver 2000 alerts/year. We find that a few events are already at reach of long baseline interferometers (CHARA, VLTI), and a rate of about 6 events/year is expected with a limiting magnitude of K~10. This number would increase by an order of magnitude by raising it to K~11. We thus expect that a new route for characterizing microlensing events will be opened by the upcoming generations of interferometers.