THE TIMING OF NINE GLOBULAR CLUSTER PULSARS

Abstract

We have used the Robert C. Byrd Green Bank Telescope to time nine previously\nknown pulsars without published timing solutions in the globular clusters M62,\nNGC 6544, and NGC 6624. We have full timing solutions that measure the spin,\nastrometric, and (where applicable) binary parameters for six of these pulsars.\nThe remaining three pulsars (reported here for the first time) were not\ndetected enough to establish solutions. We also report our timing solutions for\nfive pulsars with previously published solutions, and find good agreement with\npast authors, except for PSR J1701-3006B in M62. Gas in this system is probably\nresponsible for the discrepancy in orbital parameters, and we have been able to\nmeasure a change in the orbital period over the course of our observations.\nAmong the pulsars with new solutions we find several binary pulsars with very\nlow mass companions (members of the so-called "black widow" class) and we are\nable to place constraints on the mass-to-light ratio in two clusters. We\nconfirm that one of the pulsars in NGC 6624 is indeed a member of the rare\nclass of non-recycled pulsars found in globular clusters. We also have measured\nthe orbital precession and Shapiro delay for a relativistic binary in NGC 6544.\nIf we assume that the orbital precession can be described entirely by general\nrelativity, which is likely, we are able to measure the total system mass\n(2.57190(73) M_sun) and companion mass (1.2064(20) M_sun), from which we derive\nthe orbital inclination [sin(i) = 0.9956(14)] and the pulsar mass (1.3655(21)\nM_sun), the most precise such measurement ever obtained for a millisecond\npulsar. The companion is the most massive known around a fully recycled pulsar.\n