Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987mnras.229..517s&link_type=abstract
Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711), vol. 229, Dec. 1, 1987, p. 517-527.
Astronomy and Astrophysics
Astronomy
106
Accretion Disks, Astronomical Models, Gas Flow, Shock Waves, Spiral Galaxies, Eddington Approximation, Radiative Heat Transfer, Time Dependence
Scientific paper
Recent numerical and analytical results on disc-like accretion with shock waves as the only dissipation mechanism are compared. The global properties of the process are similar to those of the viscous (α) disc model, but precise values of the effective α value as a function of the accretion rate can be calculated. At low values of the ratio of specific heats (γ < 1.45) accretion is possible without radiative losses. Such adiabatic accretion can occur in practice at high accretion rates on to low mass objects and may be important in the formation of planets. Following Donner, and Lynden-Bell, it is pointed out that non-axisymmetric perturbations in the outer parts of a disc increase in amplitude as they propagate in and cause spiral shocks more easily in a disc than perturbations originating in the inner parts. It is suggested for this reason that the cause of spiral structure in normal spiral galaxies lies in moderate non-axisymmetries in their gaseous outer discs.
Inoue Makoto
Matsuda Takuya
Sawada Kei
Spruit Hendrik C.
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