Gravitational Microlensing I: A Unique Astrophysical Tool

TL;DR

This paper reviews gravitational microlensing as a powerful astrophysical tool for studying dark matter, stellar surfaces, and galactic structure, highlighting recent advances and future space-based observational projects.

Contribution

It provides a comprehensive overview of microlensing techniques, discusses degeneracy issues, and explores future space missions for enhanced astrophysical insights.

Findings

Microlensing can probe stellar atmospheres and surface features.

Degeneracy in lens parameters can be partially broken with perturbation effects.

Future space telescopes will improve parallax and astrometry measurements.

Abstract

In this article we review the astrophysical application of gravitational microlensing. After introducing the history of gravitational lensing, we present the key equations and concept of microlensing. The most frequent microlensing events are single-lens events and historically it has been used for searching dark matter in the form of compact astrophysical halo objects in the Galactic halo. We discuss about the degeneracy problem in the parameters of lens and perturbation effects that can partially break the degeneracy between the lens parameters. The rest of paper is about the astrophysical applications of microlensing. One of the important applications is in the stellar physics by probing the surface of source stars in the high magnification microlensing events. The astrometric and polarimetric observations will be complimentary for probing the atmosphere and stellar spots on the surface of source stars. Finally we discuss about the future projects as space based telescopes for parallax and astrometry observations of microlensing events. With this project, we would expect to produce a complete stellar and remnant mass function and study the structure of Galaxy in term of distribution of stars along our line of sight towards the centre of galaxy.