Search for exotic matter from gravitational microlensing observations of stars

TL;DR

This paper explores how exotic matter objects like wormholes and NUT metric objects can produce unique gravitational microlensing signatures, aiding their identification through detailed light curve analysis.

Contribution

It introduces the concept of small-scale spheroidal clusters of exotic matter as microlenses and predicts distinctive observational effects that differentiate them from standard Schwarzschild lenses.

Findings

Caustic crossings can produce diverse light curves.

Exotic lenses cause observable chromatic and polarizational effects.

Differences from Schwarzschild lensing can help identify exotic objects.

Abstract

We consider small-scale spheroidal clusters of weakly interacting massive particles in our Galaxy as non-compact gravitational microlenses and predict the appearance of caustics in the plane of a lensed source. The crossing of these caustics by a lensed star can produce a large variety of light curves, including some observed in actual microlensing events that have been interpreted as manifestations of binary gravitational lenses. We consider also observable effects during the gravitational microlensing of stars of non-zero angular size with a given brightness distribution across their disks by such an exotic objects as natural wormholes and objects whose space-time environment is described with the NUT metric. We demonstrate that, under certain conditions, the microlensing light curves, chromatic and polarizational effects due to the properties of the lens and the star disk brightness distributions can differ considerably from those observed for a Schwarzschild gravitational lens, so that their analysis can facilitate the identification of such objects.