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Modelling the black hole silhouette in Sagittarius A* with ion tori

Journal article
Authors O. Straub
F. H. Vincent
Marek A Abramowicz
E. Gourgoulhon
T. Paumard
Published in Astronomy & Astrophysics
Volume 543
Pages A83
ISSN 0004-6361
Publication year 2012
Published at Department of Physics (GU)
Pages A83
Language en
Keywords black hole physics, accretion, accretion disks, Galaxy: center, advection-dominated accretion, near-infrared flares, galactic-center, x-ray, synchrotron-radiation, angular-momentum, magnetic-field, central, parsec, disks, simulations, neration instrumentation, p313, rmer cd, 1991, astrophysical journal, v369, p410
Subject categories Astronomy, Astrophysics and Cosmology


We calculate the "observed at infinity" image and spectrum of the accretion structure in Sgr A*, by modelling it as an optically thin, constant angular momentum ion torus in hydrodynamic equilibrium. The physics we consider includes a two-temperature plasma, a toroidal magnetic field, as well as radiative cooling by bremsstrahlung, synchrotron, and inverse Compton processes. Our relativistic model has the virtue of being fully analytic and very simple, depending only on eight tunable parameters: the black hole spin and the inclination of the spin axis to our line of sight, the torus angular momentum, the polytropic index, the magnetic to total pressure ratio, the central values of density and electron temperature, and the ratio of electron to ion temperatures. The observed image and spectrum are calculated numerically using the ray-tracing code GYOTO. Our results demonstrate that the ion torus model is able to account for the main features of the accretion structure surrounding Sgr A*. RAMOWICZ M, 1978, ASTRONOMY AND ASTROPHYSICS, V63, P221 RAMOWICZ MA, 1995, ASTROPHYSICAL JOURNAL, V438, PL37 RAMOWICZ MA, 1983, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, V203, P323

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