89,406 research outputs found
Transonic Shocks In Multidimensional Divergent Nozzles
We establish existence, uniqueness and stability of transonic shocks for
steady compressible non-isentropic potential flow system in a multidimensional
divergent nozzle with an arbitrary smooth cross-section, for a prescribed exit
pressure. The proof is based on solving a free boundary problem for a system of
partial differential equations consisting of an elliptic equation and a
transport equation. In the process, we obtain unique solvability for a class of
transport equations with velocity fields of weak regularity(non-Lipschitz), an
infinite dimensional weak implicit mapping theorem which does not require
continuous Frechet differentiability, and regularity theory for a class of
elliptic partial differential equations with discontinuous oblique boundary
conditions.Comment: 54 page
Stability Of contact discontinuity for steady Euler System in infinite duct
In this paper, we prove structural stability of contact discontinuities for
full Euler system
Detection of X-ray-Emitting Hypernova Remnants in M101
Based on an ultra deep (230 ks) ROSAT HRI imaging of M101, we have detected 5
X-ray sources that coincide spatially with optical emission line features
previously classified as supernova remnants in this nearby galaxy. Two of these
coincidences (SNR MF83 and NGC5471B) most likely represent the true physical
association of X-ray emission with shock-heated interstellar gas. MF83, with a
radius of ~ 134 pc, is one of the largest remnants known. NGC5471B, with a
radius of 30 pc and a velocity of at least 350 km/s (FWZI), is extremely bright
in both radio and optical. The X-ray luminosities of these two shell-like
remnants are and (0.5-2 keV), about an order
of magnitude brighter than the brightest supernova remnants known in our Galaxy
and in the Magellanic Clouds. The inferred blastwave energy is for NGC5471B and ergs for MF83.
Therefore, the remnants likely originate in hypernovae, which are a factor of
more energetic than canonical supernovae and are postulated as
being responsible for Gamma-ray bursts observed at cosmological distances. The
study of such hypernova remnants in nearby galaxies has the potential to
provide important constraints on the progenitor type, rate, energetics, and
beaming effect of Gamma-ray bursts.Comment: 10 pages, 2 gif figures, Accepted for publication in Astrophysical
Journal Letter
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