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Astronomers around the world are keen and confident public communicators, with academic leaders in senior positions being the most active. They enjoy engaging with the public, with no rewards expected.
The degree of polarization of gamma-ray bursts seems to be lower than previously thought. Gamma-ray polarimetry can reveal the emission mechanism and physical information inside the relativistic jet.
KAGRA is a new gravitational wave detector being built in Japan. Unlike LIGO/Virgo, it will operate at cryogenic temperatures with sapphire mirrors. KAGRA will help improve the localization of gravitational wave detections and determination of the source parameters.
Current black hole spin measurements, in X-rays, radio and gravitational waves, are already constraining models for the growth of black holes, the dynamics of stellar core-collapse and the physics of relativistic jet production.
Supermassive black holes are fed through galaxy interactions and mergers, chaotic cold accretion in galaxy clusters and secular processes that may include stellar bars. Observations constraining these mechanisms at different scales are reviewed.
Examining and comparing many of the definitions of a black hole, it is concluded that the profusion of different definitions is a virtue that makes the investigation of black holes possible and fruitful in many different kinds of problems.
