Comment on "Understanding the $\gamma$-ray emission from the globular cluster 47 Tuc: evidence for dark matter?"

Abstract

In a recent paper Brown et al. (2018) analyze the spectral properties of the globular cluster 47 Tucanae (47 Tuc) using 9 years of Fermi-LAT data. Brown et al. (2018) argue that the emission from 47 Tuc cannot be explained by millisecond pulsars (MSPs) alone because of a significant discrepancy between the MSP spectral properties and those of 47 Tuc. It is argued that there is a significant ($>5\sigma$) preference for a two source scenario. The second component could be from the annihilation of dark matter in a density spike surrounding the intermediate-mass black hole candidate in 47 Tuc. In this paper we argue that the claimed discrepancy arises because Brown et al. (2017) use a stacked MSP spectrum to model the emission from MSPs in 47 Tuc which is insufficient to account for the uncertainties in the spectrum of the MSPs in 47 Tuc. Contrary to the claims by Brown et al. (2018), we show that the significance of an additional dark matter component is $\lesssim 2\sigma$ when sample variance in the spectrum of a population of MSPs is accounted for. The spectrum of 47 Tuc is compatible with that of a population of MSPs similar to the disk population.

arXiv comment4 pages, 2 figures

References in corpus (15)

• The Second Fermi Large Area Telescope Catalog of Gamma-ray Pulsars
• PPPC 4 DM ID: A Poor Particle Physicist Cookbook for Dark Matter Indirect Detection
• High Resolution X-ray Imaging of a Globular Cluster Core: Compact Binaries in 47Tuc
• An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae
• A Multi-Mass Velocity Dispersion Model of 47 Tucanae Indicates No Evidence for an Intermediate Mass Black Hole
• A population of gamma-ray emitting globular clusters seen with the Fermi Large Area Telescope
• Long-term observations of the pulsars in 47 Tucanae - II. Proper motions, accelerations and jerks
• The MAVERIC Survey: Still No Evidence for Accreting Intermediate-mass Black Holes in Globular Clusters
• Fermi Detection of a Luminous Gamma-ray Pulsar in a Globular Cluster
• Broadband Pulsations from PSR B1821-24: Implications for Emission Models and the Pulsar Population of M28
• The Gamma-Ray Pulsar Population of Globular Clusters: Implications for the GeV Excess
• Bayesian Model Comparison and Analysis of the Galactic Disk Population of Gamma-Ray Millisecond Pulsars
• Understanding the $\gamma$-ray emission from the globular cluster 47 Tuc: evidence for dark matter?
• Search for pulsed gamma-ray emission from globular cluster M28
• Fermi Study of gamma-ray Millisecond Pulsars: the Spectral Shape and Pulsed 25--200 GeV Emission from J0614-3329

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• The Effect of Pulsar Geometry on the Observed Gamma-ray Spectrum of Millisecond Pulsars