Gamma-ray emission from globular clusters 2MS-GC01, IC 1257, NGC5904, NGC6656 and FSR1735

TL;DR

This paper confirms gamma-ray emissions from several globular clusters using Fermi-LAT data, estimates the number of millisecond pulsars, and reports new gamma-ray detections in previously unconfirmed clusters.

Contribution

It provides new gamma-ray detections from NGC 5904, NGC 6656, and FSR 1735, expanding the known gamma-ray emitting globular clusters and estimating their MSP populations.

Findings

Confirmed gamma-ray emission from 2MS-GC01 and IC 1257.

Discovered gamma-ray emission from NGC 5904, NGC 6656, and FSR 1735.

Estimated the number of MSPs in these clusters.

Abstract

Globular clusters (GCs) are the oldest stellar system in the Galaxy, in which the millisecond pulsars are widely believed to be the only steady {\gamma}-ray emitters. So far 9 {\gamma}-ray GCs have been identified and a few candidates such as 2MS-GC01 and IC 1257 have been suggested. In this work, after analyzing the publicly-available Fermi-LAT data we confirm the significant {\gamma}-ray emission from 2MS-GC01 and IC 1257 and report the discovery for {\gamma}-ray emission from NGC 5904 and NGC 6656 within their tidal radii. Also a strong evidence of significant {\gamma}-ray emission is found from FSR 1735. From the observed {\gamma}-ray luminosities, the numbers of MSPs that are expected to be present in these GCs are estimated.