Astronomy and Astrophysics – Astrophysics
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008a%26a...482..473l&link_type=abstract
Astronomy and Astrophysics, Volume 482, Issue 2, 2008, pp.473-482
Astronomy and Astrophysics
Astrophysics
1
Accretion, Accretion Disks, Galaxies: Active, Shock Waves, Galaxies: Bl Lacertae Objects: General, Galaxies: Jets, Hydrodynamics
Scientific paper
Aims: Adopting the Smoothed Particle Hydrodynamics (SPH) numerical method, we performed a grid of evolving models of a 3D axially-symmetric, viscous accretion disc around a supermassive black hole (SMBH) of 106div 109 M&sun;. Such sort of simulations are typical of accretion discs in active galactic nuclei (AGN). In such disc models, we pay attention to the role of the specific angular momentum λ and the turbulent viscosity parameter α, according to the Shakura and Sunyaev prescription. One or two shock fronts in the radial inviscid flow develop, according to the assigned initial kinematic and thermodynamic conditions. Methods: By fixing the initial and boundary conditions on the flow at the disc outer edge, where the total energy, the specific angular momentum λ, and the initial velocity are concerned, we find pairs of (α, λ) values determining radial periodical oscillations in the shock front. In some cases, an outflow develops from the subsonic post-shock region, close to the black hole. Results: The link between the accretion disc and the jet refueling through the onset of a centrifugal shock front is evident. We also compare model variability periods with observed ones in the radio light curves of AGN.
Belvedere Gaetano
Cassaro Pietro
Costa Víctor
Lanzafame Giuseppe
Schilliro' Francesco
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