We study a solid protoplanetary core undergoing radial migration in a protoplanetary disk. We consider cores in the mass range ∼ 1 − 10 M⊕ embedded in a gaseous protoplanetary disk at different radial locations. We suppose the core luminosity is generated as a result of planetesimal accretion and calculate the structure of the gaseous envelope assuming hydrostatic and thermal equilibrium. This ...

PROSPECTS FOR DETECTING ACCRETION DISKS ASSOCIATED WITH MASSIVE STAR FORMATION Ed Churchwell University of Wisconsin Abstract It is argued that ALMA should be able to detect accretion disks associated with massive star formation during the rapid accretion phase via free-free emission from a shock-ionized envelope and via thermal dust emission after accretion ceases.

The conventional picture of disk accretion onto magnetized neutron stars has been challenged by the spin changes observed in a few X-ray pulsars, and by theoretical results from numerical simulations of diskmagnetized star interactions. These indicate possible accretion during the propeller regime and the spin-down torque increasing with the accretion rate. Here we present a model for the accre...

We present evidence for the presence of a transition in the accretion properties of radio-loud sources. For a sample of radio galaxies and radio–loud quasars, selected based on their extended radio properties, the accretion rate is estimated from the black hole mass and nuclear luminosity. The inferred distribution is bimodal, with paucity of sources at accretion rates, in Eddington units, of o...

Gas in an accretion flow is heated by MHD turbulence generated through the magneto-rotational instability. The viscous stress driving the accretion is intimately connected to the microscopic processes of turbulence dissipation. We show that, in a few well-observed black hole accretion systems, there is compelling evidence of efficient electron heating by turbulence or collective plasma effects ...

The stationary hydrodynamic equations for the transonic accretion disks and flows around rotating black holes are presented by using the Kerr-Schild coordinate where there is no coordinate singularity at the event horizon. We use two types of the causal viscosity prescription, and the boundary conditions for the transonic accretion flows are given at the sonic point. For one type of the causal ...

I review recent activity in the field of intermediate polars, concentrating on: the mode of accretion (disc-fed, disc-overflow or discless); accretion curtains (the transition region and the accretion footprint); X-ray pulse profiles (occultation and absorption effects); accretion columns (mass determinations, line-broadening, the soft X-ray component), and outbursts in intermediate polars.

We have recently realised that intermediate polars accrete in a range of modes. While accretion is predominantly through an accretion disc, in some systems the accretion stream overrows the disc and interacts with the magnetic eld directly. In RX 1712{24, discless accretion dominates. I review the current status of these observations, concentrating on the information from the X-ray lightcurves.

We report on the second phase of our study of slightly rotating accretion flows onto black holes. We consider magnetohydrodynamical (MHD) accretion flows with a spherically symmetric density distribution at the outer boundary, but with spherical symmetry broken by the introduction of a small, latitude-dependent angular momentum and a weak radial magnetic field. We study accretion flows by means...

We investigate the structure and stability of hypercritical accretion flows around stellar-mass black holes, taking into account neutrino cooling, lepton conservation, and firstly a realistic equation of state in order to properly treat the dissociation of nuclei. We obtain the radial distributions of physical properties, such as density, temperature and electron fraction, for various mass accr...