Luminosities of recycled radio pulsars in globular clusters

Abstract

Using Monte Carlo simulations, we model the luminosity distribution of recycled pulsars in globular clusters as the brighter, observable part of an intrinsic distribution and find that the observed luminosities can be reproduced using either log-normal or power-law distributions as the underlying luminosity function. For both distributions, a wide range of model parameters provide an acceptable match to the observed sample, with the log-normal function providing statistically better agreement in general than the power-law models. Moreover, the power-law models predict a parent population size that is a factor of between two and ten times higher than for the log-normal models. We note that the log-normal luminosity distribution found for the normal pulsar population by Faucher-Gigu\`ere and Kaspi is consistent with the observed luminosities of globular cluster pulsars. For Terzan~5, our simulations show that the sample of detectable radio pulsars, and the diffuse radio flux measurement, can be explained using the log-normal luminosity law with a parent population of $\sim 150$ pulsars. Measurements of diffuse gamma-ray fluxes for several clusters can be explained by both power-law and log-normal models, with the log-normal distributions again providing a better match in general. In contrast to previous studies, we do not find any strong evidence for a correlation between the number of pulsars inferred in globular clusters and globular cluster parameters including metallicity and stellar encounter rate.Comment: Accepted for publication in MNRAS; 14 pages, 10 figures and 5 table

The Galactic Millisecond Pulsar Population

“…Similar results were found by Ridley & Lorimer (2010). The log-normal form of the luminosity distribution has subsequently been adopted as a starting point by a number of other studies (e.g., Boyles et al 2011;Bagchi et al 2011 andChennamangalam et al 2012; see also these proceedings). † For example, the psrpop software package at http://psrpop.phys.wvu.edu has modules to carry out both the snapshot and evolution approaches Galactic Millisecond Pulsars 239…”

Using Long-term Millisecond Pulsar Timing to Obtain Physical Characteristics of the Bulge Globular Cluster Terzan 5

“…Globular clusters (GCs) are extraordinary factories of recycled pulsars; over the last 30 years, 146 pulsars have been discovered in Galactic GCs, with several thousands more still to be discovered (Bagchi et al 2011;Hessels et al 2015).This pulsar population is completely different from the Galactic population, with a very high fraction of pulsars with rotational periods of a few milliseconds (MSPs). One reason this happens is because GCs are very old stellar systems, so most "normal" pulsars in them have long faded into inactive neutron stars (NSs).…”

Implications of PSR J0737-3039B for the Galactic NS-NS binary merger rate

“…Hessels et al (2007) also found that the luminosity distribution of globular cluster pulsars can be described by a power-law distribution, which is similar to what is proposed by Cordes & Chernoff (1997) based on 22 millisecond pulsars (Ps < 20 ms) found in the Galactic disc. Recently, Bagchi et al (2011) analysed about a hundred recycled pulsars found in globular clusters and fit the observed pulsar luminosity distribution with powerlaw and lognormal distributions. They concluded that a lognormal distribution is a slightly better fit to the observed luminosity distribution based on the χ 2 and KolmogorovSmirnov (K-S) statistics, although both power-law and lognormal distributions are, in general, consistent with the observation.…”