Related papers: The Black Hole Explorer: Operating a Hybrid Observ…

The population of stellar origin black hole binaries (SOBHBs) detected by existing ground-based gravitational wave detectors is an exciting target for the future space-based Laser Interferometer Space Antenna (LISA). LISA is sensitive to…

The space-borne gravitational-wave (GW) detectors will open a new mass and redshift regime, allowing us to observe massive black hole binaries (MBHBs) throughout the Universe. A subset of these systems is expected to produce electromagnetic…

This paper investigates the optical appearance of a Schwarzschild-like black hole (BH) surrounded by a Dehnen-(1, 4, 5/2) type dark matter (DM) halo, with a focus on how the DM halo's density $\rho_{s}$ and radius $r_{s}$ influence the BH's…

While the energy density of the Cosmic X-ray Background (CXB) provides a statistical estimate of the super massive black hole (SMBH) growth and mass density in the Universe, the lack, so far, of focusing instrument in the 20-60 keV (where…

Ground-based gravitational-wave (GW) observatories have transformed our view of compact-object mergers, yet their reach still limits a comprehensive reconstruction of the processes that generate these systems. Only next-generation…

The primary instrument of the proposed EXIST mission is a coded mask high energy telescope (the HET), that must have a wide field of view and extremely good sensitivity. It will be crucial to minimize systematic errors so that even for very…

We present estimates for the number of supermassive black holes (SMBHs) for which the next-generation Event Horizon Telescope (ngEHT) can identify the black hole ``shadow,'' along with estimates for how many black hole masses and spins the…

We investigate systematically whether accreting black hole systems are likely to reach global alignment of the black hole spin and its accretion disc with the binary plane. In low-mass X-ray binaries (LMXBs) there is only a modest tendency…

The Event Horizon Telescope (EHT) will soon provide the first high-resolution images of the Galactic Centre supermassive black hole (SMBH) candidate Sagittarius A* (Sgr A*), enabling us to probe gravity in the strong-field regime. Besides…

The events detected by the LIGO Virgo KAGRA collaboration over a period of 10 years have yielded a treasure trove of signals from compact binary coalescences. None of these events have shown a confident signature of eccentricity. With…

The High Energy X-ray Probe is a proposed NASA probe-class mission that combines the power of high angular resolution with a broad X-ray bandpass to provide the necessary leap in capabilities to address the important astrophysical questions…

The capability of the Event Horizon Telescope (EHT) to image the nearest supermassive black hole candidates at horizon-scale resolutions offers a novel means to study gravity in its strongest regimes and to test different models for these…

A long standing goal in astrophysics is to directly observe the immediate environment of a black hole with angular resolution comparable to the event horizon. Realizing this goal would open a new window on the study of General Relativity in…

Very Long Baseline Interferometry (VLBI) provides the finest angular resolution of all astronomical observation techniques. However, observations with Earth-based instruments are approaching fundamental limits on angular resolution. These…

It is now possible to estimate black hole masses across cosmic time, using broad emission lines in active galaxies. This technique informs our views of how galaxies and their central black holes coevolve. Unfortunately, there are many…

Observations of X-ray emissions from binary systems have always been considered important tools to test the validity of General Relativity in strong-field regimes. The pairs and triplets of high frequency quasi-periodic oscillations…

We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of ~40 micro-as, consistent with the size and shape of the lensed…

Simultaneous gravitational and electromagnetic wave observations of merging black hole binaries (BHBHs) can provide unique opportunities to study gravitation physics, accretion and cosmology. Here we perform fully general relativistic,…

The International Space Station offers a unique platform for rapid and inexpensive deployment of space telescopes. A scientific opportunity of great potential later this decade is the use of telescopes for the electromagnetic follow-up of…

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ($<10"$ FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far superior to current facilities' (including XMM-Newton and…