We review observations of ultraluminous X-ray sources (ULXs). X-ray spectroscopic and
timing studies of ULXs suggest a new accretion state distinct from those seen in Galactic …

Intermediate-mass black holes (IMBHs), with masses in the range 1 0 0–1 0 6 M⊙, are the
link between stellar-mass BHs and supermassive BHs (SMBHs). They are thought to be the …

Aims. During the last~ 50 years, the population of black hole candidates in X-ray binaries
has increased considerably, with 59 Galactic objects being detected in transient low-mass X …

Ultraluminous X-ray sources are extragalactic objects located outside the nucleus of the host
galaxy with bolometric luminosities exceeding 1039 erg s-1. These extreme luminosities—if …

We derive the luminosity–temperature relation for the supercritically accreting black holes
(BHs) and compare it to the data on ultraluminous X-ray sources (ULXs). At super-Eddington …

Black hole binaries with extreme (≳ 10 4: 1) or intermediate (∼ 10 2–10 4: 1) mass ratios
are among the most interesting gravitational wave sources that are expected to be detected …

We investigate the effect of nonevaporating primordial black holes (PBHs) on the ionization
and thermal history of the universe. X-rays emitted by gas accretion onto PBHs modify the …

We revisit the question of the nature of ultraluminous X-ray sources (ULXs) through a
detailed investigation of their spectral shape, using the highest quality X-ray data available …

Most ultraluminous X-ray sources have a typical set of properties not seen in Galactic stellar-
mass black holes. They have luminosities of more than 3× 1039 ergs per second, unusually …

(abridged) The review describes observations of SS433. The main difference between
SS433 and other X-ray binaries is the supercritical regime for the gas accretion onto the …