Gamma-rays from millisecond pulsars in Globular Clusters

TL;DR

This paper reviews gamma-ray observations of globular clusters, discussing how their evolved stellar populations and compact objects like millisecond pulsars contribute to high-energy emissions detected by Fermi and Cherenkov telescopes.

Contribution

It provides a comprehensive review of gamma-ray detection results from globular clusters and discusses recent models explaining their high-energy emission mechanisms.

Findings

Gamma-ray emission detected from several GCs by Fermi.

Cherenkov telescopes set upper limits constraining GC models.

Observations support the role of millisecond pulsars in gamma-ray production.

Abstract

Globular clusters (GCs) with their ages of the order of several billion years contain many final products of evolution of stars such as: neutron stars, white dwarfs and probably also black holes. These compact objects can be at present responsible for the acceleration of particles to relativistic energies. Therefore, gamma-ray emission is expected from GCs as a result of radiation processes occurring either in the inner magnetosperes of millisecond pulsars or in the vicinity of accreting neutron stars and white dwarfs or as a result of interaction of particles leaving the compact objects with the strong radiation field within the GC. Recently, GeV gamma-ray emission has been detected from several GCs by the new satellite observatory Fermi. Also Cherenkov telescopes reported interesting upper limits at the TeV energies which start to constrain the content of GCs. We review the results of these gamma-ray observations in the context of recent scenarios for their origin.