We present an analytical model of SNR evolution in a cloudy interstellar medium for a single progenitor star of spectral type 05 V. The model begins with the progenitor on the zero-age main sequence, includes the effects of the star’s wind and ionizing photons, and ends with the SNR’s assimilation by the ISM. We assume that the ISM consists of atomic clouds, molecular clouds, and a hot intercloud phase. The type of SNR that results bears a strong resemblance to N63A in the Large Magellanic Cloud.

The evolution of young supernova remnants has been modeled using a 1-dimensional hydrodynamic code. Turbulent dynamo amplification of magnetic fields and both turbulent and shock acceleration of relativistic electrons have been included macroscopically to produce synchotron radiation. The observed radio morphology cannot be reproduced by expansion into a homogeneous medium; it appears that many small cloudlets must be present in the circumstellar material.

A small HI absorption feature has been detected in front of Cas A at a velocity of -66 km/s. This HI feature can probably be associated with a recombined high density QSF.

VRO 42.05.01 (G166.0+4.3) is a SNR which has broken into and re-energized an old interstellar cavity. Observations of HI in a field containing the SNR show features associated with it. An expanding shell of mass ∼40 M⊙ is associated with the semi-circular shell of the SNR. The cavity, which the SNR has re-energized, is seen in the HI. A cloud of HI of mass ∼25 M⊙ has apparently been hit by the shock and has been accelerated by the post-shock flow.

The presence of interstellar clouds along the northern and eastern edges of Puppis A is revealed by our HI and CO observations.

New radio continuum and spectral line observations of the Galactic radio source G18.95-1.1 are reported. The distance to G18.95-1.1 is 2 kpc as derived from HI-21 cm spectral line observations. These data also indicate an interaction with the interstellar medium. The radio continuum observations classify G18.95-1.1 as a composite supernova remnant.

We observed the semicircular supernova remnant G109.1-1.0 in the J = 1-0 transition of CO with the Nobeyama 45-m radio telescope. It is found that two remarkably thin molecular filaments delineate the inner boundary of the X-ray jet feature in this remnant. These filaments seem to have experienced evaporation due to the hot gas in the remnant.

A program of CO observations of five selected supernova remnants is in progress on the 4-m radio telescope at Nagoya. Here, we report observations of two supernova remnants, G78.2+2.1 (the γ Cygni SNR) and HB21. In these two remnants we have obtained evidence for the interaction between the supernova remnants and molecular gas.

High resolution (∼36“×90”) radio maps of SNRs W28 and W44 observed with the OSRT at 327 MHz are presented. The distortions or dents in their shell structure are associated with the parts of the shells expanding into dense molecular clouds in their vicinity and provide direct observational evidence for interaction between them.

Most supernova remnants (SNRs) in our galaxy have been discovered from their radio emission and for the majority this remains the only means of studying them. In this review the impact of new radio observations is discussed.

The increased detail of recent radio maps reveals some common patterns among SNRs, despite their generally diverse appearance. The patterns can give us clues to both the intrinsic properties of the supernova and the influence of the interstellar medium. With a fuller understanding of individual remnants, there are better prospects for meaningful interpretation of statistical studies.

Variations in ambient density can largely account for: slope and extent of the observed Σ-D relations, the slope of about +1 of the cumulative N-D relation, and the increase of Eo with D as derived from optical line data. Emin increases during the evolution; the behaviour of Ex remains uncertain.

The results of a VLA study of the radio continuum properties of supernova remnants in the nearby spiral galaxy M33 are presented. It is shown that a relationship exists between the radio surface brightnesses and the diameters of the 13 detected supernova remnants. The significance of the relation and the constraints it imposes on models of SNR evolution are discussed.

Based on radio continuum surveys of the Galactic plane at wavelengths of 21 cm and 11 cm we have so far identified about 32 new supernova remnants in the area 357°.4 ≤ℓ≤ 76°. |b| ≤ 5°. This increases the number of known objects in this field by about 68%. Most of them are in the Galactic latitude range |b| 〉 0°.5. Some implications are discussed.

Radio continuum observations, obtained with the DRAO Synthesis Telescope, are presented of the new supernova remnant (SNR) G73.9+0.9. Our map at 1420 MHz shows indications of spatially resolved knots of emission in the brightest part of the remnant. The 408 MHz map, although of lower resolution, shows the same general morphology. The spectral index α (Sv∝v−α) between 1420 and 408 MHz is about 0.5, a value typical for shell type SNRs. The morphology however is more suggestive of a filled centre SNR.

G160.9+2.6 (HB9) is a supernova remnant of large angular diameter and low radio surface brightness. We report new observations of the continuum emission from HB9 at 408 MHz and 1420 MHz with angular resolutions of 3.5’ and 1.0#x2019;, respectively, which reveal significant filamentary structure not previously detected. The 1420 MHz field covers only the central and eastern parts of HB9. The 408-1420 MHz spectral index (S∝vα) of regions common to both maps is α=-0.68, with no significant spatial variation. The radio filamentary structure closely follows the optical structure. X-ray emission from HB9 is more centrally concentrated than the radio or optical emission. The radio, optical, and particularly, the X-ray surface brightness are all diminished in the northern and northwestern portions of the remnant, in directions approximately coincident with an extensive molecular cloud detected in CO.

We describe in this work the results of high frequency radio continuum observations of 96 supernova remnants (SNRs) obtained at the Itapetinga Observatory at 22 GHz. We have detected 15 SNRs. Most of the strongest SNRs detected were previously classified in terms of their spectral and morphological properties as filled-center type (Crab-like). Some of the others have doubtful classifications.

Some recent developments in the theory of particle acceleration at supernova shock fronts are reviewed and the confrontation of this theory with measurements of galactic cosmic rays and observations of supernova remnants is discussed. Supernova shock waves are able to account for the energetics, spectrum and composition of galactic cosmic rays, though it remains difficult to understand acceleration of ∼ 105 GeV particles. Recent developments in the analysis of interplanetary shock waves and in the numerical simulation of quasi-parallel shocks are encouraging. Interpretations of different categories of remnants are reviewed and a speculative interpretation of the optical companion to SN1987a is discussed.

Supernova remnants can reaccelerate cosmic rays and modify their distribution during the cosmic ray propagation in the galaxy. Cosmic ray observations (in particular the boron-to-carbon data) strongly limit the permitted amount of reacceleration, which is used to set an upper limit on the expansion of supernova remnants, and a lower limit on the effective density of the ISM swept up by supernova shocks. The constraint depends on the theory of cosmic ray propagation: the standard Leaky Box model requires a high effective density, > 1cm−3, and is probably inconsistent with the present picture of the ISM. Modifying the Leaky Box model to include a moderate amount of weak-shock reacceleration, a self consistent solution is found, where the effective density in this solution is ≈ 0.1 cm−3, which implies efficient evaporation of the warm ISM component by young supernova remnants, during most of their supersonic expansion.

Recent VLA observations of the shell supernova remnant SN 1006 AD (Reynolds and Gilmore 1986) and the Crablike remnant 3C 58 (SN 1181 AD?; Reynolds and Aller 1987) show features at high resolution that contain information on details of particle acceleration and transport in the remnants. Thin arcs at the edge of SN 1006 require time-variable particle acceleration and/or magnetic field amplification. Filaments in 3C 58 probably result from interaction of pulsar-generated relativistic fluid with filaments of thermal gas formed early in the remnant’s life by cooling or dynamical instabilities. Their sharp edges imply efficient scattering by Alfvén waves; as much as 1% of the large-scale magnetic energy density may be in magnetic turbulence on length scales of 1011 cm.

Prior to conducting a survey of the galactic plane at 327 MHz using the VLA, we have imaged four fields near galactic longitude of 20 degrees. Each image will cover a 2.5 degree field with ∼1 arcmin resolution. The fields have been chosen to include the remnants G20.0-0.2, G21.5-0.9, and G24.7+0.6. The first two are isolated Crab-like objects, that is, there is no discernible associated shell. Since such shells have relatively steep spectra, images at 327 MHz will be more sensitive to their presence. The absence of a shell can constrain the density of the ISM in the vicinity of the SNR (Reynolds and Aller 1985 A.J. 90, 2312). Since ∼50% of Crabs are naked, the implications can be extended to a significant fraction of the ISM.