Extended source effect on microlensing light curves by an Ellis wormhole

TL;DR

This paper explores how extended sources affect microlensing light curves caused by Ellis wormholes, demonstrating that their unique demagnification signatures can be distinguished from Schwarzschild lenses under certain conditions.

Contribution

It provides the first detailed analysis of extended source effects on microlensing light curves by Ellis wormholes, highlighting observable differences from traditional lenses.

Findings

Extended sources reduce the gutter depth in light curves.

Distinct shape differences allow identification of Ellis wormholes.

Detection is feasible for specific star velocities and wormhole sizes.

Abstract

We can survey an Ellis wormhole which is the simplest Morris-Thorne wormhole in our galaxy with microlensing. The light curve of a point source microlensed by the Ellis wormhole shows approximately $4\%$ demagnification while the total magnification of images lensed by a Schwarzschild lens is always larger than unity. We investigate an extended source effect on the light curves microlensed by the Ellis wormhole. We show that the depth of the gutter of the light curves of an extended source is smaller than the one of a point source since the magnified part of the extended source cancels the demagnified part out. We can, however, distinguish between the light curves of the extended source microlensed by the Ellis wormhole and the ones by the Schwarzschild lens in their shapes even if the size of the source is a few times larger than the size of an Einstein ring on a source plane. If the relative velocity of a star with the radius of $10^6$ km at $8$ kpc in the bulge of our galaxy against an observer-lens system is smaller than $10$ km/s on a source plane, we can detect microlensing of the star lensed by the Ellis wormhole with the throat radius of $1$ km at $4$ kpc.