2 research outputs found
Supernova Asymmetries and Pulsar Kicks -- Views on Controversial Issues
Two- and three-dimensional simulations demonstrate that hydrodynamic
instabilities can lead to low-mode (l=1,2) asymmetries of the fluid flow in the
neutrino-heated layer behind the supernova shock. This provides a natural
explanation for aspherical mass ejection and for pulsar recoil velocities even
in excess of 1000 km/s. We propose that the bimodality of the pulsar velocity
distribution might be a consequence of a dominant l=1 mode in case of the fast
component, while higher-mode anisotropy characterizes the postshock flow and SN
ejecta during the birth of the slow neutron stars. We argue that the observed
large asymmetries of supernovae and the measured high velocities of young
pulsars therefore do not imply rapid rotation of the iron core of the
progenitor star, nor do they require strong magnetic fields to play a crucial
role in the explosion. Anisotropic neutrino emission from accretion contributes
to the neutron star acceleration on a minor level, and pulsar kicks do not make
a good case for non-standard neutrino physics in the nascent neutron star.Comment: 10 pages, 5 figures, full resolution figures available on request or
from Preprint P-MPA1651e on MPA web page. In: The Fate of the Most Massive
Stars, Proc. Eta Carinae Science Symposium (Jackson Hole, May 2004); revision
discusses new Cas A observation
Damping of supernova neutrino transitions in stochastic shock-wave density profiles
Supernova neutrino flavor transitions during the shock wave propagation are
known to encode relevant information not only about the matter density profile
but also about unknown neutrino properties, such as the mass hierarchy (normal
or inverted) and the mixing angle theta_13. While previous studies have
focussed on "deterministic" density profiles, we investigate the effect of
possible stochastic matter density fluctuations in the wake of supernova shock
waves. In particular, we study the impact of small-scale fluctuations on the
electron (anti)neutrino survival probability, and on the observable spectra of
inverse-beta-decay events in future water-Cherenkov detectors. We find that
such fluctuations, even with relatively small amplitudes, can have significant
damping effects on the flavor transition pattern, and can partly erase the
shock-wave imprint on the observable time spectra, especially for
sin^2(theta_13) > O(10^-3).Comment: v2 (23 pages, including 6 eps figures). Typos removed, references
updated, matches the published versio