Photometric, Astrometric and Polarimetric observations of gravitational microlensing events

TL;DR

This paper explores how photometric, astrometric, and polarimetric observations of gravitational microlensing can reveal details about stars and their trajectories, highlighting the potential for large telescopes to observe polarization signals in a subset of events.

Contribution

It demonstrates the advantages of combining polarimetric and astrometric data in microlensing to study stellar surfaces and trajectories, supported by analysis of OGLE catalog events.

Findings

Polarization signals are observable in about 4.3% of microlensing events with large telescopes.

Polarimetric and astrometric observations can reveal star surface features and lensing trajectories.

The study provides a framework for utilizing these observations in future microlensing research.

Abstract

The gravitational microlensing as a unique astrophysical tool can be used for studying the atmosphere of stars thousands of parsec far from us. This capability results from the bending of light rays in the gravitational field of a lens which can magnify the light of a background source star during the lensing. Moreover, one of properties of this light bending is that the circular symmetry of the source is broken by producing distorted images at either side of the lens position. This property makes the possibility of the observation of the polarization and the light centroid shift of images. Assigning vectors for these two parameters, they are perpendicular to each other in the simple and binary microlensing events, except in the fold singularities. In this work, we investigate the advantages of polarimetric and astrometric observations during microlensing events for (i) studying the surface of the source star and spots on it and (ii) determining the trajectory of source stars with respect to the lens. Finally we analyze the largest sample of microlensing events from the OGLE catalog and show that for almost ~ 4.3 per cent of events in the direction of the Galactic bulge, the polarization signals with large telescopes would be observable.