Luminosities of recycled radio pulsars in globular clusters

Authors

  • Manjari Bagchi,

    Corresponding author
    1. Department of Physics, 210 Hodges Hall, West Virginia University, Morgantown, WV 26506, USA
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  • D. R. Lorimer,

    1. Department of Physics, 210 Hodges Hall, West Virginia University, Morgantown, WV 26506, USA
    2. National Radio Astronomy Observatory, Green Bank Observatory, PO Box 2, Green Bank, WV 24944, USA
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  • Jayanth Chennamangalam

    1. Department of Physics, 210 Hodges Hall, West Virginia University, Morgantown, WV 26506, USA
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E-mail: Manjari.Bagchi@mail.wvu.edu

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. We find that the observed luminosities can be reproduced using either lognormal 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 lognormal 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 2 and 10 times higher than for the lognormal models. We note that the lognormal luminosity distribution found for the normal pulsar population by Faucher-Giguère 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 lognormal luminosity law with a parent population of ∼150 pulsars. Measurements of diffuse gamma-ray fluxes for several clusters can be explained by both power-law and lognormal models, with the lognormal 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.

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