The supernova remnant (SNR) E0102.2-72.2 is the brightest in the Small Magellanic Cloud (SMC) at X-ray wavelengths. This object, which is remarkable because of its high velocity (∼4000 km s−1) oxygen-rich optical emission, appears to be similarly remarkable at X-ray wavelengths. The high resolution imager (HRI) data can be quite well described by a thick ring with a radius of ∼19" (6 pc at a distance of 63 kpc). The imaging proportional counter (IPC) X-ray spectral data can be best fit by a single emission line of energy ∼0.9 keV. It seems likely that this is the emission from a plasma of almost pure neon.

We use Einstein FPCS observations of lines of highly ionized neon, silicon and sulfur to constrain the parameters of the supernova remnant Cas A.

We reexamine the X-ray emission from Tycho’s remnant using results from hydrodynamic models computed with a detailed spherically symmetric code. The observed synchrotron radio contours (Green and Gull 1983) appear to require a cloudy circumstellar medium (Dickel and Jones, 1985; Dickel, Eilek, and Jones 1987), thus we explore the X-ray emission properties of similar models. We find that they tend to produce broad shells of X-ray emission that resemble the observed X-ray map of Tycho (Seward, Gorenstein, and Tucker 1983). A simple hydrodynamic model can satisfy both radio and X-ray observations, but it has little similarity to the evolution of remnants in cloudy media dominated by thermal conduction (McKee and Ostriker 1977). More work needs to be done to ensure that the spectrum as well as the X-ray map can be modeled with the same cloudy circumstellar medium, although we believe it will not be difficult to obtain as good a statistical agreement with the spectral data as other models have achieved (e.g. Hamilton, Sarazin, and Szymkowiak 1986).

X-ray observations of young supernova remnants (SNR) provide the most direct tool to study their evolution, their chemical composition, and their interaction with the interstellar medium. We will show for a SNR with the characteristics of Tycho that great care has to be taken in interpreting spectral data obtained with X-ray detectors with low spatial resolution.

We present NEI hydrodynamical models of Kepler’s SNR compared with the EXOSAT and EINSTEIN X-ray spectra.

We have synthesized a set of SNR X-ray and coronal iron surface brightness profiles to determine observational constraints to help distinguish how the remnants’ ion-electron energy equilibration time-scales compare to their ionization time-scales. The profiles are based on Sedov-Taylor blast wave models under the two scenarios (1) equal Tion and Te or (2) Coulomb equilibration of Te and Tion. Resultant spectra were convolved with Einstein HRI and IPC sensitivity curves to simulate satellite observations of actual remnants.

The thermal X-ray emission from SN 1987A may be enhanced to a detectable level when the blast shock hits the circumstellar medium which has formed in the red-supergiant stage of the progenitor.

The X-ray spectrum of Tycho observed with the satellite Tenma can be explained approximately within the context of a carbon deflagration model for Type la supernovae, if the ejecta are assumed to be mixed partially.

High resolution X-ray spectral observations of Puppis A were performed with the FPCS on Einstein. We use plasma diagnostics of lines from OVII and OVIII to constrain the values of temperature, ionization timescale, and hydrogen column density.

A complete X-ray image of the SNR PKS1209-52 (= G296.5+10.0) was obtained with the IPC and HRI on the Einstein Observatory. The remnant has a shell-like X-ray morphology much like its appearance at radio wavelengths, while a compact X-ray source is clearly detected near the center of the remnant. The flux observed from the X-ray nebula F(0.1−4.5 keV) is 8 × 10−11 ergs cm−2 s−1, which corresponds to a luminosity L(0.1−4.5 keV) = 8 × 1035 ergs s−1 for a distance of 2 kpc. Applying a simple shell model to the X-ray emission distribution, we derived an ambient interstellar medium nO = 0.08 H atoms cm−3, total X-ray emitting plasma mass 150 M⊙, and thermal energy 1.2 × 1050 ergs. The flux from the compact X-ray source F(0.15−4.5 keV) is ~2 × 10−12 ergs cm−2 s−1. There are no obvious optical counterparts brighter than mv ~ 22 within the 3.3″ radius HRI error circle. If the object is a hot neutron star, the HRI/IPC count rate ratio implies a surface temperature of 1.6 × 106 K for NH = 3.2 × 1021 cm−2.

This review discusses the observations and theoretical models of interstellar shock waves in diffuse and molecular clouds. After summarizing the relevant gas dynamics, atomic, molecular and grain processes, and physics of radiative and magnetic precursors, I describe observational diagnostics of shocks. I conclude with a discussion of two new topics: unstable or non-steady shocks and thermal conduction in metal-rich shocks.

The high molecular abundances seen in IC443 may be due to hot chemistry in shocked gas or to an increase in the cosmic ray ionization rate. New calculations reported here show that shock chemistry dominates over the relevant short time scale.

Combining new spectrophotometric data on the Orion and Crab Nebulae with detailed calculations, we show that strong [Ni II] λ7378 emission observed in numerous SNR’s may be associated with gas having Ne > 50,000 cm−3.

We report ultraviolet and optical spectra of IE 0102-7219, the oxygen-rich supernova remnant in the Small Magellanic Cloud. The UV data contain strong lines of oxygen, carbon, neon, and magnesium. OI recombination lines in the optical and UV permit the relative line intensities to be determined from 1200Å to 1 micron. Models assuming shock excitation and X-ray photoionization have been calculated and compared with the observations.

A new area-spectroscopy search for sulfur as a tracer of the “Si Group” of elements in the ejecta of the young SNRs, LMC N132D and SMC 1E0102.2–7219, yields negative results for [S II]λλ6719, 6731 and [S III]λλ9064, 9532.

We have obtained long slit echelle spectroscopy for 10 of the brightest supernova remnants in M33 using the KPNO 4 m telescope. The profiles at Hα indicate bulk motions in the range 100–350 km s−1 in these remnants. Nearly all of the objects show signs of contamination by low velocity H II emission at some level. This affects the line intensities measured from low resolution data and may affect diameter measurements of these remnants.

Existing catalogues of supernova remnants (SNRs) in external galaxies are very incomplete. Potentially however, such samples are of great importance in understanding SNRs, since the distances to objects in a given sample are essentially the same and since absorption is small (compared to galactic SNRs). We have recently obtained Hα+[NII], Hβ, [SII], [OIII], and 6100 Å continuum CCD images of nine selected areas in M33 using the KPNO 4m. In addition to the six SNRs already known to exist in the fields we have surveyed, we have identified 21 other nebulae with [SII]:Hα+[NII] ratios which may be SNRs. Spectra of seven of these nebulae were obtained subsequently and show that the majority are indeed SNRs. A more detailed analysis of regions containing significant HII region contamination and a search for very small diameter remnants is currently underway.

Giant HII regions contain large numbers of massive stars, and hence are expected to contain large numbers of SNRs. Until recently, however, only a few SNRs have been identified in extragalactic giant HII regions. Moreover, most of these SNRs are located at the outskirts of HII regions, instead of the core where most of the stars are located. The low detection rate and the outlying locations of the SNRs may be due to: 1) observational difficulties - the background HII regions are much more luminous than the SNRs in both optical line emission and radio continuum; 2) intrinsic invisibility of SNRs - stellar wind and SNRs may have created a supershell (Mac Low and McCray 1987), and the core of a giant HII region is filled with hot tenuous coronal gas; or 3) a genuine deficiency of supernovae and SNRs in the HII regions (Sramek and Weedman 1986).

The inhomogeneity of the interstellar medium (ISM) has a profound effect on the propagation of the interstellar shock generated by a supernova and on the appearance of the resulting supernova remnant (SNR). Low mass supernovae produce remnants that interact with the “pristine” ISM, which has density inhomogeneities (clouds) on a wide range of scales. The shock compresses and accelerates the clouds it encounters; inside the blast wave, the clouds are hydrodynamically unstable, and mass is injected from the clouds into the intercloud medium. Embedded clouds interact thermally with the shock also, adding mass to the hot intercloud medium via thermal evaporation or subtracting it via condensation and thermal instability. Mass injection into the hot intercloud medium, whether dynamical or thermal, leads to infrared emission as dust mixes with the hot gas and is thermally sputtered. The remnants of massive supernovae interact primarily with circumstellar matter and with interstellar material which has been processed by the ionizing radiation and wind of the progenitor star. After passing through any circumstellar material which may be present, the shock encounters a cavity which tends to “muffle” the SNR. The remnants of massive supernovae therefore tell us more about the late stages of the evolution of massive stars than about the ISM.

A numerical simulation of shock propagation in a clumpy medium with a weak magnetic field is presented which illustrates a number of dynamical processes of potential importance for explaining spectral line width and radio polarization measurements in supernova remnants.

The interactions of supernovae ejecta with the surrounding medium which have a dominant influence on the resulting SNR dynamics and brightness are considered for both young and evolved objects. The important roles of clumpy ejecta in determining the brightness of young SNR and of shock impingement on a pre-existing shell in influencing both the brightness and subsequent dynamics of evolved SNR are stressed.