Instability of a stalled accretion shock: evidence for the advective-acoustic cycle
| dc.creator | Foglizzo, T. | |
| dc.creator | Galletti, P. | |
| dc.creator | Scheck, L. | |
| dc.creator | Janka, H. -Th. | |
| dc.date | 2006-06-26 | |
| dc.date | 2006-09-21 | |
| dc.date.accessioned | 2026-07-07T10:39:24Z | |
| dc.date.available | 2026-07-07T10:39:24Z | |
| dc.description | We analyze the linear stability of a stalled accretion shock in a perfect gas with a parametrized cooling function L ~ rho^{beta-alpha} P^alpha. The instability is dominated by the l=1 mode if the shock radius exceeds 2-3 times the accretor radius, depending on the parameters of the cooling function. The growth rate and oscillation period are comparable to those observed in the numerical simulations of Blondin & Mezzacappa (2006). The instability mechanism is analyzed by separately measuring the efficiencies of the purely acoustic cycle and the advective-acoustic cycle. These efficiencies are estimated directly from the eigenspectrum, and also through a WKB analysis in the high frequency limit. Both methods prove that the advective-acoustic cycle is unstable, and that the purely acoustic cycle is stable. Extrapolating these results to low frequency leads us to interpret the dominant mode as an advective-acoustic instability, different from the purely acoustic interpretation of Blondin & Mezzacappa (2006). A simplified characterization of the instability is proposed, based on an advective-acoustic cycle between the shock and the radius r_nabla where the velocity gradients of the stationary flow are strongest. The importance of the coupling region in this mechanism calls for a better understanding of the conditions for an efficient advective-acoustic coupling in a decelerated, nonadiabatic flow, in order to extend these results to core-collapse supernovae. | |
| dc.description | 29 pages, 18 figures, to appear in ApJ (1 new Section, 2 new Figures) | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0606640 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0606640 | |
| dc.identifier | Astrophys.J.654:1006-1021,2007 | |
| dc.identifier | doi:10.1086/509612 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/181016 | |
| dc.subject | Astrophysics | |
| dc.title | Instability of a stalled accretion shock: evidence for the advective-acoustic cycle | |
| dc.type | text |