The first stars in the universe, forming at redshifts z > 15 in minihalos with masses of order 10M⊙, may leave behind black holes as their remnants. These objects could conceivably serve as "seeds" for much larger black holes observed at redshifts z . 7. We study the growth of the remnant black holes through accretion including for the first time the emitted accretion radiation with adaptive me...

Gravitomagnetic precession near neutron stars and black holes has received much recent attention, particularly as a possible explanation of 15È60 Hz quasi-periodic brightness oscillations (QPOs) from accreting neutron stars in low-mass X-ray binaries, and of somewhat higher frequency QPOs from accreting stellar-mass black holes. Previous analyses of this phenomenon have either ignored radiation...

Recent hydrodynamical simulations of radiatively inefficient black hole accretion flows with low viscosity have demonstrated that these flows differ significantly from those described by an advection-dominated model. The black hole flows are advectiondominated only in their inner parts, but convectively dominated at radii R ∼ > 10RG. In such flows, the radiative output comes mostly from the con...

In a number of the most luminous ULXs (those with LX ∼ 10 40 erg s) in nearby galaxies, observations with XMM-Newton and Chandra are revealing evidence which suggests that these ULXs may harbor intermediate-mass black holes (IMBHs). The detection of accretion disk spectral components with temperatures 5–10 times lower than the temperatures observed in stellar-mass black hole binaries near to th...

www.physicstoday.org After decades of effort, numerical relativists can now simulate the inspiral and merger of two black holes orbiting each other. That computational triumph has come none too soon—physicists are on the verge of detecting gravitational waves for the first time, and at long last they know what to look for. Black holes are strong-field objects whose properties are governed by Ei...

We discuss how disk models may limit the scope of identifying astrophysical black holes. We show that the standard Keplerian thin disk model, the thick disk model, slim disks, ADAFs etc. are fundamentally limited. We present the most complete solution to date called the advective accretion disk and discuss how it has the scope to address every observational aspects of a black hole. Though the m...

We calculate the jet power of the classical Blandford-Znajek (BZ) model and hybrid model developed by Meier based on the global solutions of advection dominated accretion flows (ADAFs) surrounding Kerr black holes. We find that the jet power of the hybrid model is larger than that of the pure BZ model. The jet power will dominate over the accretion power, and the objects will enter into “jet-po...

The Fermi and Swift satellites, together with ground based Cherenkov telescopes, has greatly improved our knowledge of blazars, namely Flat Spectrum Radio Quasars and BL Lac objects, since all but the most powerful emit most of their electro–magnetic output at γ–ray energies, while the very powerful blazars emit mostly in the hard X–ray region of the spectrum. Often they show coordinated variab...

The radio emission from supermassive black holes in nearby early-type galaxies can be used to test possible explanations for their low luminosities. We calculate the expected contribution from thermal synchrotron emission from hot accretion flows to the high radio frequency observations of NGC 2300, NGC 1399, NGC 4278 and NGC 4594. We find that, in all cases, and in accordance with our previous...