Very compact objects probe extreme gravitational fields and may be the key to understand
outstanding puzzles in fundamental physics. These include the nature of dark matter, the …

The spin of a black hole is an important quantity to study, providing a window into the
processes by which a black hole was born and grew. Furthermore, spin can be a potent …

We review the properties and behavior of 20 X-ray binaries that contain a dynamically-
confirmed black hole, 17 of which are transient systems. During the past decade, many of …

General relativity has passed all solar system experiments and neutron star based tests,
such as binary pulsar observations, with flying colors. A more exotic arena for testing …

Astrophysical black hole candidates are thought to be the Kerr black holes of general
relativity, but there is not yet direct observational evidence that the spacetime geometry …

Relativistic reflection features are commonly observed in the X-ray spectra of accreting black
holes. In the presence of high quality data and with the correct astrophysical model, X-ray …

The spins of ten stellar black holes have been measured using the continuum-fitting method.
These black holes are located in two distinct classes of X-ray binary systems, one that is …

Black holes (BHs) in general relativity (GR) are very simple objects. This property, that goes
under the name of'no-hair', has been refined in the last few decades and admits several …

We study the electrodynamics of a kinetically mixed dark photon cloud that forms through
superradiance around a spinning black hole, and design strategies to search for the …

Stellar-mass black holes and neutron stars represent extremes in gravity, density, and
magnetic fields. They therefore serve as key objects in the study of multiple frontiers of …