Fermi Detection of a Luminous Gamma-ray Pulsar in a Globular Cluster

Abstract: We report the Fermi Large Area Telescope detection of gamma-ray (>100 megaelectronvolts) pulsations from pulsar J1823-3021A in the globular cluster NGC 6624 with high significance (~7 sigma). Its gamma-ray luminosity L_gamma = (8.4 +/- 1.6) x10^34 ergs per second, is the highest observed for any millisecond pulsar (MSP) to date, and it accounts for most of the cluster emission. The non-detection of the cluster in the off-pulse phase implies that its contains < 32 gamma-ray MSPs, not ~100 as previously estimated. The gamma-ray luminosity indicates that the unusually large rate of change of its period is caused by its intrinsic spin-down. This implies that J1823-3021A, has the largest magnetic field and is the youngest MSP ever detected, and that such anomalous objects might be forming at rates comparable to those of the more normal MSPs.