Published in

Oxford University Press (OUP), Monthly Notices of the Royal Astronomical Society, 1(486), p. 851-867, 2019

DOI: 10.1093/mnras/stz898

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Milky Way globular clusters in γ-rays: analysing the dynamical formation of millisecond pulsars

Journal article published in 2019 by Raniere de Menezes, Fabio Cafardo ORCID, Rodrigo Nemmen
This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Data provided by SHERPA/RoMEO

Abstract

ABSTRACT Globular clusters (GCs) are evolved stellar systems containing entire populations of millisecond pulsars (MSPs), which are efficient γ-ray emitters. Observations of this emission can be used as a powerful tool to explore the dynamical processes leading to binary system formation in GCs. In this work, 9 yr of Fermi Large-Area Telescope data were used to investigate the γ-ray emission from all GCs in the Milky Way. Twenty-three clusters were found as γ-ray bright, with two of them never having been reported before. It was also found that magnetic braking probably has a smaller impact on the formation rate of binary systems in metal-rich GCs than previously suggested, while a large value for the two-body encounter rate seems to be a necessary condition. The influence of the encounter rate per formed binary was for the first time explored in conjunction with γ-ray data, giving evidence that if this quantity is very high, binary systems will get destroyed before having time to evolve into MSPs, thus decreasing the total number of MSPs in a GC. No extended emission was found even for clusters whose optical extent is ≈0.5°; all of them are point-like sources spatially in agreement with the optical cores of the GCs, supporting previous X-ray results of heavier objects sinking into the clusters’ cores via dynamical friction. The possibility of extrapolating these results to ultra-compact dwarf galaxies is discussed, as these systems are believed to be the intermediate case between GCs and dwarf galaxies.

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