Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...448l.109j&link_type=abstract
Astrophysical Journal Letters v.448, p.L109
Astronomy and Astrophysics
Astronomy
66
Stars: Supernovae: General, Hydrodynamics, Shock Waves, Convection, Turbulence
Scientific paper
One- and two-dimensional hydrodynamical simulations of the neutrino-driven supernova explosion of a 15 M&sun; star are performed for the phase between stagnation of the prompt shock and 1 s after core bounce. Variation of the neutrino ( nu ) fluxes from the nu sphere shows that explosion energy and timescale, initial proto--neutron star mass, and explosive nucleosynthesis of Fe group elements depend sensitively on the strength of the nu heating during the first few 100 ms after shock formation. Convective overturn in the nu -heated region behind the shock is a crucial help for the explosion only in a narrow window of nu luminosities. Here powerful explosions can be obtained only in the multidimensional case, primarily because the overturn increases the efficiency of nu energy deposition by allowing cool postshock matter to penetrate inward to the region of strongest heating, while heated gas can quickly rise outward, thus reducing its energy loss due to reemission of neutrinos. This interpretation is supported by the different increase of the explosion energy with time in one- and two-dimensional models. For higher core nu fluxes spherically symmetrical models also yield energetic explosions, while for lower luminosities even with convection, no strong explosions occur. Cool gas in downflows from the shock to the heating zone loses leptons by nu e emission but gains energy by interactions with the core nu fluxes. However, because it does not get very n rich and its entropy increases, it is not accreted into the low-entropy, neutronized surface of the neutron star. Because of the absence of significant accretion while the explosions develop on a timescale of a few 100 ms, the initial proto--neutron star (baryonic) masses are only ~1.2 M&sun;. Turbulent activity around the neutron star is transient; at 200--300 ms after shock formation, the turbulent layer decouples from the nu -heated zone and moves outward behind the supernova shock. The shock shows deformation on large scales. Inhomogeneities of temperature T, density rho , and velocity with contrasts of order unity on scales of 30 deg--45 deg in the shell behind the shock could help to explain anisotropies and radial mixing observed in SN 1987A. When the supernova shock reaches the entropy step of the Si-O interface at 5700 km about 400--500 ms after bounce, the rho inversion between the dense shell and the low-density, "hot bubble" region around the neutron star begins to steepen into a strong reverse shock that forms a sharp discontinuity in the nu -driven wind from the nascent neutron star. The deceleration of the wind expansion might trigger significant, anisotropic fallback of matter to the neutron star on a timescale of several seconds.
Janka Hans-Thomas
Mueller Ewald
No associations
LandOfFree
The First Second of a Type II Supernova: Convection, Accretion, and Shock Propagation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The First Second of a Type II Supernova: Convection, Accretion, and Shock Propagation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The First Second of a Type II Supernova: Convection, Accretion, and Shock Propagation will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1269053