January 11, 1995
Similar papers 3
January 3, 2023
Supernova remnants (SNRs), the products of stellar explosions, are powerful astrophysical laboratories, which allow us to study the physics of collisionless shocks, thanks to their bright electromagnetic emission. Blast wave shocks generated by supernovae (SNe) provide us with an observational window to study extreme conditions, characterized by high Mach (and Alfvenic Mach) numbers, together with powerful nonthermal processes. In collisionless shocks, temperature equilibrati...
November 22, 1999
We present new radio observations of the supernova SN 1979C made with the VLA at 20, 6, 3.6, and 2 cm from 1991 July to 1998 October, which extend our previously published observations (Weiler et al.1986, 1991), beginning 8 days after optical maximum in 1979 April and continuing through 1990 December. We find that the radio emission from SN 1979C has stopped declining in flux density in the manner described by Weiler et al. (1992), and has apparently entered a new stage of ev...
January 21, 2000
In present study I examine the capability of diffusive shock acceleration mechanism to explain existing data on radio emission from evolved large diameter shell-type adiabatic supernova remnants (SNRs). Time-dependent ''onion-shell'' model for the radio emission of SNRs is developed, which is based on the assumptions: a) acceleration takes place from thermal energies and test-particle approximation is valid; b) the problem of injection is avoided by introducing, like Bell (19...
September 13, 2021
The remnant of SN 1987A is the best-studied object of its kind. The rich data-set of its thermal and non-thermal emission across the electromagnetic spectrum poses a unique testbed for the elaboration of particle-acceleration theory. We use 2D simulations of the progenitor's wind to obtain hydro-profiles for the medium around the supernova explosion. Various cones along prominent features of the ambient medium are then used in our time-dependent acceleration code RATPaC to ...
March 13, 2000
We have extended a simple model of nonlinear diffusive shock acceleration (Berezhko and Ellison 1999) to include the injection and acceleration of electrons and the production of photons from bremsstrahlung, synchrotron, inverse-Compton, and pion-decay processes. We argue that the results of this model, which is simpler to use than more elaborate ones, offer a significant improvement over test-particle, power-law spectra which are often used in astrophysical applications of d...
September 8, 2004
Without amplification, magnetic fields in expanding ejecta of young supernova remnants (SNRs) will be orders of magnitude below those required to shock accelerate thermal electrons, or ions, to relativistic energies or to produce radio synchrotron emission at the reverse shock. The reported observations of such emission give support to the idea that diffusive shock acceleration (DSA) can amplify magnetic fields by large factors. Furthermore, the uncertain character of the amp...
December 27, 1996
We present seven years of radio observations of SN 1987A made with the Australia Telescope Compact Array. At 1.4, 2.4, 4.8 and 8.6 GHz, the flux density of the radio remnant has increased monotonically since emission was redetected 1200 days after the explosion. On day 3200, the remnant was expanding at 2800 +/- 400 km/s, which we interpret as indicating significant deceleration of the fastest moving ejecta. Since day 1787 the spectral index has remained constant at alpha = -...
July 6, 2001
We are investigating the SN 1987A remnant by modeling the circumstellar environment of the progenitor star. Interacting stellar winds models have been reasonably successful at reproducing the gross features of the nebula, but some details, such as the early rise of the radio and x-ray emission from the supernova blast and the presence of the outer rings, are not explained in a pure wind model. In this paper we describe preliminary results from 2-D models that incorporate the ...
April 21, 2015
Recent observations by the Large Area Telescope (LAT) onboard the Fermi satellite have revealed bright gamma-ray emission from middle-aged supernova remnants (SNRs) inside our Galaxy. These remnants, which also possess bright non-thermal radio shells, are often found to be interacting directly with surrounding gas clouds. We explore the non-thermal emission mechanism at these dynamically evolved SNRs by constructing a hydrodynamical model. Two scenarios of particle accelerati...
July 2, 1998
The radio light curves of SN 1993J are found to be well fit by a synchrotron spectrum, suppressed by external free-free absorption and synchrotron self-absorption. A standard r^-2 circumstellar medium is assumed, and found to be adequate. The magnetic field and number density of relativistic electrons behind the shock are determined. The strength of the magnetic field argues strongly for turbulent amplification behind the shock. The ratio of the magnetic and thermal energy de...