Femto-lensing due to a Cosmic String
Abstract
We consider the femto-lensing due to a cosmic string. If a cosmic string with the deficit angle 100 [femto-arcsec] 10-18 [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.
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