Numerical simulations of composite supernova remnants for smallσpulsar wind nebulae

Abstract

Context. Composite supernova remnants consist of a pulsar wind nebula located inside a shell-type remnant. The presence of a shell has implications on the evolution of the nebula, although the converse is generally not true. Aims. The purpose of this paper is two-fold. The first aim is to determine the effect of the pulsar's initial luminosity and spin-down rate, the supernova ejecta mass, and density of the interstellar medium on the evolution of a spherically-symmetric, composite supernova remnant expanding into a homogeneous medium. The second aim is to investigate the evolution of the magnetic field in the pulsar wind nebula when the the composite remnant expands into a non-uniform interstellar medium. Methods. The Euler conservation equations for inviscid flow, together with the magnetohydrodynamic induction law in the kinematic limit, are solved numerically for a number of scenarios where the ratio of magnetic to particle energy is σ < 0.01. The simulations in the first part of the paper is solved in a one-dimensional configuration. In the second part of the paper, the effect of an inhomogeneous medium on the evolution is studied using a two-dimensional, axisymmetric configuration. Results. It is found that the initial spin-down luminosity and density of the interstellar medium has the largest influence on the evolution of the pulsar wind nebula. The spin-down time-scale of the pulsar only becomes important when this value is smaller than the time needed for the reverse shock of the shell remnant to reach the outer boundary of the nebula. For a remnant evolving in a non-uniform medium, the magnetic field along the boundary of the nebula will evolve to a value that is larger than the magnetic field in the interior. If the inhomogeneity of the interstellar medium is enhanced, while the spin-down luminosity is decreased, it is further found that a magnetic "cloud" is formed in a region that is spatially separated from the position of the pulsar.

Radio observations of the region around the pulsar wind nebula HESS J1303−631 with ATCA

“…While the pulsar is still inside the SNR, its nebula is strongly disrupted by the reverse shock of the remnant (see e.g. Blondin et al 2001;Vorster et al 2013a) and at the moment of interaction with the shell it is very small. Moving outside the remnant the pulsar builds up a new nebula which can become very large due to the proper motion of the pulsar, i.e.…”

Multi-Wavelength Modeling of Globular Clusters—the Millisecond Pulsar Scenario

“…The transport of charged energetic particles, here electrons and possibly positrons, in phase space (space and momentum) can be prescribed by a Fokker-Planck-type equation such as the Parker equation (Parker 1965) that includes diffusion (spatial and momentum), convection, sources, and linear losses (see, e.g., Kopp et al (2012) for a more general discussion of this type of equation). If spatial convection can be neglected (see Vorster et al 2013 for the inclusion of the latter in an application to pulsar wind nebulae), we obtain…”

Review of the Theory of PWNe

“…More recently de Jager et al (2008) have used a 1-D model to compute the evolution of an injected distribution function, and to compute an integrated spectrum for G21.5-0.9. Latest results have been presented by Vorster et al (2013).…”