Discovery of gamma-ray pulsations of PSR J1835$-$3259B in the Globular Cluster NGC 6652

Abstract

Motivated by the newly discovery of a spin period 1.83\,ms pulsar J1835$-$3259B in the globular cluster (GC) NGC~6652, we analyze the gamma-ray data obtained with the Large Area Telescope (LAT) onboard {\it Fermi Gamma-ray Space Telescope (Fermi)} for the GC and detect the pulsations of this millisecond pulsar (MSP) at a 5.4$\sigma$ confidence level (the weighted H-test value is $\sim 41$). From timing analysis of the data, a pulse profile that is similar to the radio one is established. We thus consider that we have detected the \gr\ emission of the MSP, and discuss the implications. Based on our analysis results and different studies of the sources in the GC, the observed gamma-ray emission from the GC could mainly arise from this MSP, like the previous two cases the GCs NGC~6624 and NGC~6626. Assuming this is the case, the pulsar, at the GC's 9.46\,kpc distance and having a spin-down luminosity of $\leq 4.3\times 10^{35}$ erg s$^{-1}$, would have a gamma-ray luminosity of $\simeq (5.04\pm0.44)\times 10^{34}$ erg s$^{-1}$ and a gamma-ray efficiency of $\gtrsim 0.12$.