Galaxies, Volume 10, Issue 4

Gravitational waves (GW) are propagating perturbations of the space-time metric, generated by time-varying mass distributions [...]

Cosmic Explorer is a concept for a new laser interferometric observatory in the United States to extend ground-based gravitational-wave astrophysics into the coming decades. Aiming to begin operation in the 2030s, Cosmic Explorer will extend current...

A brief summary is given of an alternative interpretation of the Event Horizon Telescope observations of the massive black hole in the nucleus of the nearby galaxy M87. It is proposed that the flow is primarily powered by the black hole rotation, not...

Deep space exploration offers the most profound opportunity for the expansion of humanity and our understanding of the universe but remains extremely challenging. Progress will continue to be paced by uncrewed missions followed up by crewed missions...

We review results from the POLAMI program, which monitors the polarization properties of 36 blazars at the IRAM 30 m telescope. We found that the variability of the degree of linear polarization is faster and of higher amplitude at 1 mm than at 3 mm...

As part of the Advanced Virgo upgrade for the O5 observation run in 2026, a more powerful laser and larger end mirrors in the Fabry–Perot cavities will be installed. The new optical configuration will increase the laser beam waist in the cryoge...

In this review, we discuss various open-source software for modeling the broadband emission of extragalactic sources from radio up to the highest gamma-ray energies. As we provide an overview of the different tools available, we discuss the physical...

The source, origin, and acceleration mechanisms of ultra-high-energy cosmic rays (UHECR) ($E>{10}^{20}$ eV, beyond the GZK limit) remain uncertain and unclear. The main explanations are associated with particular mechanisms, such as the Fermi mechanism,...

The investigation about cosmic-ray sources through the study of the arrival direction of the particles is completely dependent on primary mass compositions. This is due to heavier particles having an average larger deflection during propagation in ga...

This Special Issue is dedicated to the memory of the physicist Professor James Maxwell Bardeen (9 May 1939–20 June 2022), who is well known for his work on general relativity, particularly his role in formulating the laws of black hole mechanic...

Planetary nebulae (PNe) are the progeny of low- and intermediate-mass stars, at the exact time in their late evolution when they eject their hydrogen-rich envelopes and start their transition towards white dwarfs [...]

One of the fundamental conclusions of the Cosmic Battery (a means for producing poloidal magnetic flux in the vicinity of a black hole via the Poynting-Robertson effect on the accretion disk) is that it determines the direction of the axial magnetic...

Neutron stars provide a unique physical laboratory in which to study the properties of matter at high density and temperature. We study a diagnostic of the composition of high-density matter, namely, g-mode oscillations, which are driven by buoyancy...

Studies of Gamma-Ray Burst (GRB) properties, such as duration and spectral hardness, have found evidence for additional classes, beyond the short/hard and long/soft prototypes, using model-dependent methods. In this paper, a model-independent approac...

Studies of Gamma-ray Burst (GRB) properties, such as duration and spectral hardness, have found evidence for additional classes beyond the short-hard (merger) and long-soft (collapsar) prototypes. Several clustering analyses of the duration-hardness...

On 11 February 2016, the LIGO and Virgo scientific collaborations announced the first direct detection of gravitational waves, a signal caught by the LIGO interferometers on 14 September 2015, and produced by the coalescence of two stellar-mass black...