81 research outputs found
High-Frequency Voronoi Noise Reduced by Smoothed Mesh Motion
We describe a technique for improving the performance of hydrodynamics codes
which employ a moving Voronoi mesh. Currently, such codes are susceptible to
high-frequency noise produced by rapid adjustments in the grid topology on the
smallest scales. The treatment for this grid noise is simple; instead of moving
the mesh-generating marker points with the local fluid velocity, this velocity
field is smoothed on small scales, so that neighboring marker points generally
have similar velocities. We demonstrate significant improvement gained by this
adjustment in several code tests relevant to the physics which moving-mesh
codes are designed to capture.Comment: MNRAS Accepte
Supernova Explosions from Accretion Disk Winds
Winds blown from accretion disks formed inside massive rotating stars may
result in stellar explosions observable as Type Ibc and Type II supernovae. A
key feature of the winds is their ability to produce the radioactive Nickel-56
necessary to power a supernova light curve. The wind strength depends on
accretion disk cooling by neutrino emission and photo-disintegration of bound
nuclei. These cooling processes depend on the angular momentum of the stellar
progenitor via the virial temperature at the Kepler radius where the disk
forms. The production of an observable supernova counterpart to a Gamma-Ray
Burst (GRB) may therefore depend on the angular momentum of the stellar
progenitor. Stars with low angular momentum may produce a GRB without making an
observable supernova. Stars with large angular momentum may make extremely
bright and energetic supernovae like SN 1998bw. Stars with an intermediate
range of angular momentum may simultaneously produce a supernova and a GRB.Comment: 7 pages, to appear in Proc. "From Twilight to Highlight - The Physics
of Supernovae" ESO/MPA/MPE Workshop, Garching July 200
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