Fermi Detection of a Luminous γ-Ray Pulsar in a Globular Cluster

We report the Fermi Large Area Telescope detection of γ-ray (>100 MeV) pulsations from pulsarJ1823−3021A in the globular clusterNGC 6624 with high significance (∼7 σ). Its γ-ray luminosity Lγ = (8.4 ±1.6) × 1034 erg s−1 is the highest observed for any millisecond pulsar(MSP) to date, and it accounts for most of the cluster emission. The nondetection of the cluster in the off-pulse phase implies that it contains <32 γ-ray MSPs, not ∼100 as previously estimated. The γ-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.