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Young and massive stellar clusters are a potential source of galactic cosmic rays due to at least two acceleration mechanisms. Collective stellar winds from massive stars form a wind-blown bubble with a termination shock at which particle…

IceCube, a cubic-kilometer sized neutrino detector at the Geographic South Pole, has recently discovered a diffuse all-flavor flux of astrophysical neutrinos. However, the corresponding astrophysical sources have not yet been identified in…

The beaming pattern of radiation emitted by a relativistically moving source like jets in microquasars, AGN and GRBs, is a key issue for understanding of acceleration and radiation processes in these objects. In this paper we introduce a…

The arrival directions of ultra-high-energy cosmic rays appear to be approximately isotropically distributed over the whole sky, but the last-generation UHECR detector arrays, the Pierre Auger Observatory (Auger) and the Telescope Array…

Precision measurements of neutron star radii can provide a powerful probe of the properties of cold matter beyond nuclear density. Beginning in the late 1970s it was proposed that the radius could be obtained from the apparent or inferred…

The LHAASO observatory has recently measured details of the cosmic-ray (CR) spectrum in the knee region (1 -- 10 PeV) with unprecedented precision, including its average CR mass composition and the spectrum of the proton component. We use…

An analysis of the environments around a sample of 28 3CR radio galaxies with redshifts 0.6 < z < 1.8 is presented, based primarily upon K--band images down to K ~ 20 taken using the UK Infrared Telescope (UKIRT). A net overdensity of…

The Exeter FCRAO CO Galactic Plane Survey consists of 12CO and 13CO (J=1-0) observations over the galactic plane covering 55 degrees <= l <= 102 degrees, |b| >= 1 degree and 141 degrees <= l <= 195 degrees, -3.5 degrees <= b <= 5.5 degrees…

KM3NeT/ARCA is a Cherenkov neutrino telescope under construction in the Mediterranean sea, optimised for the detection of astrophysical neutrinos with energies above $\sim$1~TeV. In this work, using Monte Carlo simulations including…

In this article I review the main theoretical problems that are posed by the highest energy end of the observed cosmic ray spectrum, stressing the importance of establishing their composition in order to decide between proposed scenarios. I…

Over the next year, a new era of observations of compact objects in X-ray polarization will commence. Among the key targets for the upcoming Imaging X-ray Polarimetry Explorer mission, will be the magnetars 4U 0142+61 and 1RXS…

We present an analysis of the 2-point correlation function, of the X-ray Brightest Abell-type Cluster sample (XBACs; Ebeling et al. 1998) and of the cosmological constraints that it provides. If \xi(r) is modelled as a power-law, we find…

We present constraints on isotropic cosmic birefringence induced by axion-like particles (ALPs), derived from the analysis of cosmic microwave background (CMB) polarization measurements obtained with the high-frequency channels of Planck.…

We address the effect of the viewing angle of the accretion disk plane and the geometry of the broad-line region (BLR) with the goal of interpreting the distribution of quasars along the main sequence (MS). We utilize photoionization code…

In a series of paper, it has been shown that the distribution of polarisation position angles for visible light from quasars is not random in extremely large regions of the sky. As explained in a recent article, the measurement of vanishing…

Cosmic rays travelling through interstellar space have their propagation directions repeatedly scattered by fluctuating interstellar magnetic fields. The nature of this scattering is a major unsolved problem in astrophysics, one that has…

We discuss and compare two alternative models for the two-point angular correlation function of galaxies detected through the sub-millimetre emission using the Herschel Space Observatory. The first, now-standard Halo Model, which represents…

X-ray and optical observations of quadruply lensed quasars can provide a microarcsecond probe of the lensed quasar, corresponding to scale sizes of \~10^2-10^4 gravitational radii of the central black hole. This high angular resolution is…

The symmetry axes of active galactic nuclei (AGN) are randomly distributed in space but highly inclined sources are heavily obscured and are not seen as quasars with broad emission lines. The obscuring torus geometry determines the average…

The aureoles around stars caused by thin cirrus limit nighttime measurement opportunities for ground-based astronomy but can provide information on high-altitude ice crystals for climate research. In this paper we attempt to demonstrate…