Citation for published item:frownD enthony wF nd vroixD homs nd vloydD heridn nd foehmD g¡ eline nd ghdwikD ul @PHIVA 9nderstnding the Ery emission from the gloulr luster RU u X evidene for drk mtterc9D hysil review hFD WV @RAF HRIQHI@AF Further information on publisher's website: eprinted with permission from the emerin hysil oietyX frownD enthony wFD vroixD homsD vloydD heridnD foehmD g¡ eline ghdwikD ul @PHIVAF nderstnding the Ery emission from the gloulr luster RU uX ividene for drk mtterc hysil eview h WV@RAX HRIQHI@AF @PHIVA y the emerin hysil oietyF eders my viewD rowseD ndGor downlod mteril for temporry opying purposes onlyD provided these uses re for nonommeril personl purposesF ixept s provided y lwD this mteril my not e further reproduedD distriutedD trnsmittedD modi(edD dptedD performedD displyedD pulishedD or sold in whole or prtD without prior written permission from the emerin hysil oietyF Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. 47 Tuc was the first globular cluster observed to be γ-ray bright, with the γ rays being attributed to a population of unresolved millisecond pulsars (MSPs). Recent kinematic data combined with detailed simulations appear to be consistent with the presence of an intermediate mass black hole (IMBH) at the center of 47 Tuc. We analyze nine years of Fermi-LAT observations to study the spectral properties of 47 Tuc with unprecedented accuracy and sensitivity. This nine-year γ-ray spectrum shows that 47 Tuc's γ-ray flux cannot be explained by MSPs alone due to a systematic discrepancy between the predicted and observed flux. Rather, we find a significant preference (TS ¼ 40) for describing 47 Tuc's spectrum with a two source population model consisting of an ensemble of MSPs and annihilating dark matter (DM) with an enhanced density around the IMBH when compared to a MSP-only explanation. The best-fit DM mass of 34 GeV is essentially the same as the best-fit DM explanation for the Galactic center "excess" when assuming DM annihilation into bb quarks. Our work constitutes the first possible evidence of dark matter within a globular cluster.

Axion-like-particles (ALPs) emitted from the core of magnetars can convert to photons in the strong magnetic field of the magnetosphere. We study such emissions in the soft gamma-ray range from 300 keV to 1 MeV, where the ALP spectrum peaks and astrophysical backgrounds from resonant Compton upscattering are expected to be suppressed. Using published quiescent soft-gamma flux upper limits in 6 Magnetars obtained with CGRO COMPTEL, INTE-GRAL SPI/IBIS/ISGRI and the Fermi Gamma Ray Burst Monitor (GBM), we put limits on the ALP-photon coupling obtained from conversions, assuming that ALP emission from the core is just sub-dominant to bounds from neutrino cooling. For core temperatures of 10 9 K, the constraints on the ALP-photon coupling coming from magnetars 1E 2259+586 and J170849.0-400910 are better than the current limits obtained from the CAST experiment. We provide a detailed study of the dependence of our results on the magnetar core temperature. Our results motivate a program of studying quiescent soft gamma ray emission from magnetars in the 300 keV -1 MeV band with the Fermi -GBM.

We analyse 8 years of PASS 8 Fermi-LAT data, in the 60 MeV -300 GeV energy range, from 30 high Galactic latitude globular clusters. Six of these globular clusters are detected with a TS > 25, with NGC 6254 being detected as gamma-ray bright for the first time. The most significant detection is of the well-known globular cluster 47 Tuc, and we produce a refined spectral fit for this object with a log parabola model. NGC 6093, NGC 6752 and NGC 6254 are fitted with hard, flat power law models, NGC 7078 is best fitted with a soft power law and NGC 6218 is best fitted with a hard, broken power law. This variety of spectral models suggests that there is a variety of γ-ray source types within globular clusters, in addition to the traditional millisecond pulsar interpretation. We identify a correspondence between diffuse X-ray emission in globular cluster cores and gamma-ray emission. This connection suggests that gammaray emission in globular clusters could also arise from unresolved X-ray sources or a relativistic electron population, perhaps generated by the millisecond pulsars. X-ray observations of further gamma-ray bright globular clusters would allow a functional relationship to be determined between diffuse X-ray and gamma-ray emission.

We analyze 9 years of pass 8 Fermi -LAT data in the 60−500 MeV range and determine flux upper limits (UL) for 17 gamma-ray dark pulsars as a probe of axions produced by nucleon-nucleon Bremsstrahlung in the pulsar core. Using a previously published axion decay gamma-ray photon flux model for pulsars which relies on a high core temperature of 20 MeV, we improve the determination of the UL axion mass (m a ), at 95 percent confidence level, to 9.6 × 10 -3 eV, which is a factor of 8 improvement on previous results. We show that the axion emissivity (energy loss rate per volume) at realistic lower pulsar core temperatures of 4 MeV or less is reduced to such an extent that axion emissivity and the gamma-ray signal becomes negligible. We consider an alternative emission model based on energy loss rate per mass to allow m a to be constrained with Fermi -LAT observations. This model yields a plausible UL m a of 10 -6 eV for pulsar core temperature <0.1 MeV but knowledge of the extent of axion to photon conversion in the pulsar B field would be required to make a precise UL axion mass determination. The peak of axion flux is likely to produce gamma-rays in the ≤ 1 MeV energy range and so future observations with medium energy gamma-ray missions, such as AMEGO and e-ASTROGAM, will be vital to further constrain UL m a .

The Gamma-ray Cherenkov Telescope (GCT) is one of the telescopes proposed for the Small Sized Telescope (SST) section of CTA. Based on a dual-mirror Schwarzschild-Couder design, which allows for more compact telescopes and cameras than the usual single-mirror designs, it will be equipped with a Compact High-Energy Camera (CHEC) based on silicon photomultipliers (SiPM). In 2015, the GCT prototype was the first dual-mirror telescope constructed in the prospect of CTA to record Cherenkov light on the night sky. Further tests and observations have been performed since then. This report describes the current status of the GCT, the results of tests performed to demonstrate its compliance with CTA requirements, and the optimisation of the design for mass production. The GCT collaboration, including teams from Australia, France, Germany, Japan, the Netherlands and the United Kingdom, plans to install the first telescopes on site in Chile for 2019-2020 as part of the CTA pre-production phase.