Neutrino-cooled Accretion Disks around Spinning Black Holes
Abstract
We calculate the structure of accretion disks around Kerr black holes for accretion rates M˙=0.001-10 Msolar s-1. Such high-M˙ disks are plausible candidates for the central engine of gamma-ray bursts. Our disk model is fully relativistic and accurately treats the microphysics of the accreting matter: neutrino emissivity, opacity, electron degeneracy, and nuclear composition. The neutrino-cooled disk forms above a critical accretion rate M˙ign that depends on the black hole spin. The disk has an ``ignition'' radius rign where neutrino flux rises dramatically, cooling becomes efficient, and the proton-to-nucleon ratio Ye drops. Other characteristic radii are rα, where most of α-particles are disintegrated, rν, where the disk becomes ν-opaque, and rtr, where neutrinos get trapped and advected into the black hole. We find rα, rign, rν, and rtr and show their dependence on M˙. We discuss the qualitative picture of accretion and present sample numerical models of the disk structure. All neutrino-cooled disks regulate themselves to a characteristic state such that: (1) electrons are mildly degenerate, (2) Ye~0.1, and (3) neutrons dominate the pressure in the disk.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2007
- DOI:
- 10.1086/508923
- arXiv:
- arXiv:astro-ph/0607145
- Bibcode:
- 2007ApJ...657..383C
- Keywords:
-
- Accretion;
- Accretion Disks;
- Dense Matter;
- Gamma Rays: Bursts;
- Astrophysics
- E-Print:
- 35 pages, 18 figures, accepted to ApJ