Femto-lensing due to a Cosmic String

TL;DR

This paper explores how femto-lensing caused by cosmic strings with tiny tension can produce observable interference patterns in gamma-ray burst spectra, offering a new method to detect such cosmic strings.

Contribution

It proposes using femto-lensing effects in gamma-ray bursts to detect cosmic strings with extremely small tension, expanding the application of gravitational lensing techniques.

Findings

Femtolensing can produce detectable interference patterns in gamma-ray spectra.

Cosmic strings with very small tension can be probed through femto-lensing.

Differences between point mass lensing and cosmic string lensing are analyzed.

Abstract

We consider the femto-lensing due to a cosmic string. If a cosmic string with the deficit angle $\Delta\sim 100$ [femto-arcsec] $\sim10^{-18}$ [rad] exists around the line of sight to a gamma-ray burst, we may observe characteristic interference patterns caused by gravitational lensing in the energy spectrum of the gamma-ray burst. This "femto-lensing" event was first proposed as a tool to probe small mass primordial black holes. In this paper, we propose use of the femto-lensing to probe cosmic strings with extremely small tension. Observability conditions and the event rate are discussed. Differences between the cases of a point mass and a cosmic string are presented.