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Measurements of Fe XIV 5303-A and Fe X 6374-A forbidden emission from several supernova remnants are reported, and their relation to X-ray observations is discussed. The brightest Fe XIV forbidden-emission region in Puppis A is interpreted as being the result of the supernova shock wave's interacting with a dense cloud in the interstellar medium.
Evidence for weak soft X-ray emission from the remnant of Kepler's supernova has been acquired by the low energy detectors of the A 2 experiment on HEAO 1. A soft X-ray source has been detected using a narrow field of view sensitive to X rays between 0.2 and 3 keV and is found to be the only constant X-ray source within the error box containing Kepler's supernova remnant. The intensity of the X-ray source is calculated to be about 6.3 x 10 to the -2 counts/sq cm sec, with an intrinsic X-ray luminosity in the energy range 0.3 to 3 keV of about 28 x 10 to the 35 erg/sec if, as is widely believed, the remnant is at a distance of 4 kpc. Observations from HEAO 2 will allow the detection to be confirmed, the source to be imaged and its spectrum to be determined.
The nature of type 1 supernovae (SN 1) is discussed through a comparison of observational evidence and theoretical perspectives relating to both type 1 and 2 supernovae. In particular two hypotheses relating to SN 1 phenomenon are examined: the first proposing that SN 1 are components of binary systems in which, at a comparatively late stage of evolution, overflow of the mass occurs; the second considers pre-SN 1 to be recently evolved stars with a mass greater than 1.4 solar mass (white dwarfs). In addition, an explanation of the reduced frequency of flares of SN 1 in spiral galaxies as related to that in elliptical galaxies is presented.
The thermal conditions leading to the rapid nucleation and growth of dust in astronomical explosions are examined. The contribution to nucleation physics lies only in the clarification of the ambient conditions where it apparently occurs. In both nova and interior shells of supernovae, dust precipitates in gas densities of the order of 10 to the -14th g/cu cm a few months after the explosion. The ambient conditions differ widely, however. Supernova condensation occurs in a thermal equilibrium, with photons, ions, electrons, and grains having equal temperatures. In novae huge disequilibria exist, with photon and electron temperatures near 50,000 K, photon energy density near 750 K, and forming refractory grains near 1800 K. In neither type of explosion can the condensed matter easily maintain chemical equilibrium with the total system. Interesting isotopic anomalies are trapped in both types of refractory condensate in the interstellar medium. The nova provides the best astronomical laboratory for observing the condensation.
The number of known X-ray emitting supernova remnants in our galaxy has significantly grown as a result of the soft X-ray survey by the HEAO-1 spacecraft. The HEAO-1 A-2 experiment has observed soft X-ray emission from the old supernova remnant HB9 which lies close to the previously identified X-ray source, Capella. Spectral data and the low optical obscuration in the direction of the remnant suggest that HB9 is a good candidate for detecting Fe XIV coronal forbidden-line emission. Mapping of the coronal line emission in association with the imaging X-ray data expected from HEAO-2 would allow the temperature profile of the emitting shell to be determined in a manner similar to that used by Tuohy, Nousek, and Garmire (1979) for the Cygnus Loop, which is in a similar evolutionary phase to HB9.
The soft X-ray data from the low energy detectors of the HEAO 1 A-2 experiment are surveyed in the 0.15-3.0 keV range to search for X-ray bursts (less than 1 hour) from extragalactic supernovae predicted by Klein and Chevalier. To within the operating sensitivity of 0.08 photons per sq cm/s no events were discovered from the first 8 months of operation. This is consistent with the theoretical prediction that the probability of finding one such event is small. The HEAO 2 satellite should be capable of detecting supernovae out to 2000 Mpc; these events are of cosmological interest.
The present status of theories of presupernova stellar evolution and the triggering mechanisms of supernova explosions are reviewed. The validity of the single-star approximation for stellar core evolution is considered, and the central density and temperature of the stellar core are discussed. Attention is then given to the results of numerical models of supernova explosions by carbon deflagration of an intermediate mass star, resulting in the total disruption of the star; the photodissociation of iron nuclei in a massive star, resulting in neutron star or black hole formation; and stellar core collapse triggered by electron capture in stars of mass ranging between those of the intermediate mass and massive stars, resulting in neutron star formation despite oxygen deflagration. Helium and carbon combustion and detonation in accreting white dwarfs and the gravitational collapse triggered by electron-pair creation in supermassive stars are also discussed, and problems requiring future investigation are indicated.
Soft X-ray observations of the X-ray source H1122-59 in the 0.4-2 keV band made with the low-energy detector 1 of the HEAO A-2 experiment are described. Based on positional coincidence, the source is identified with the supernova remnant MSH-11-54, thus confirming the report of Share et al. (1980). The object is a bright source in the 0.4-2 keV band with an X-ray flux of 9 x 10 to the -11th ergs/sq cm s near the earth. The measured source spectrum implies a plasma temperature of 4 million K and X-ray luminosity in the 0.4-2 keV band of 10 to the 37th ergs/s using a distance of 10 kpc for MSH 11-54. The X-ray observations, interpreted in terms of an adiabatic shock wave model, give a shock velocity of about 560 km/s and a supernova age of about 2300 yr, in good agreement with the age derived from the radio observations.
A simple model is given for the infrared light-echo from a supernova explosion in a molecular cloud. The color temperature is determined by the vaporization temperature of the dust grains, and the time scale is given by the light travel time across the distance to which grains are vaporized. For typical parameters, a supernova exploding in a cloud with a density of approximately 10,000/cu cm at a distance of 10 kpc produces a flux of approximately 60,000 Jy at 3.5 microns for 150 days.
The X-ray spectra of supernova remnants are discussed, and their implications for the emission mechanism are considered. A model-fitting procedure for analyzing spectral information is presented, and alternative data presentations are indicated. Model spectra expected from diffuse X-ray sources, in which X-ray transfer effects are minimized, are calculated for the cases of Compton interactions, synchrotron radiation and bremsstrahlung. The emission mechanisms of supernova remnants are then considered, and it is pointed out that whereas it is certain that the X radiation from the Crab pulsar arises from synchrotron emission, the kinetic mechanisms giving rise to X-ray emission in the nonpulsar SNRs are not understood. Results of Einstein Observatory solid state spectrometer measurements of the Cas A, Tycho and Puppis A are then presented which are fit by two-temperature thermal spectra, and the Crab SNR, fit by a power-law model. Spectral trends in the older and younger SNRs are pointed out, and the role of Einstein imaging data in future detailed modeling necessary to convert apparent abundances into true abundances is indicated.
The superposition of the X-ray, optical, and radio imagery of supernova remnants in the Cygnus Loop region is described. The radio data of the region was obtained using the Westerbork interferometer, and the optical image was recorded by the NASA Wide Field Camera. The X-ray imagery was obtained using the High Resolution Imager. The mechanisms by which the supernova ejecta and the swept-up material shock the interstellar medium are studied by the resampling of the imagery onto a common celestial grid. The initial results indicate a radio arc in the northeastern portion of the region that is along the faintest outermost filaments, and a separate radio arc along the brightest filaments.
The possibility of detecting grains formed in supernovae by observations of their emission in the infrared is examined. The basic processes determining the temperature and infrared radiation of grains in supernova environments are analyzed, and the results are used to estimate the infrared emission from the highly metal enriched fast moving knots in Cas A. The predicted fluxes lie within the reach of current ground-based facilities at 10 microns, and their emission should be detectable throughout the infrared band with cryogenic space telescopes.
Strong interstellar absorption lines of C I, arising from the two excited fine-structure levels, are found in IUE observations of HD 72350 (type B4 III). An analysis of the excited-level populations of C I gives local temperature and pressure limits, and auxiliary data on the limit of column density for excited O I and the carbon ionization help to establish that (1) the local temperature is within the limits of 25-100 K, and (2) the pressure/Boltzmann's constant ratio is at least 10 to the 4.3/cu cm K, despite its small size. This high-pressure cloud is discussed in terms of shock compression by the Vela supernova blast wave, along with the relationship of this kind of cloud compression to star formation and to the origin of the characteristic filamentary emission arcs seen in Vela and other supernova remnants
The first order Fermi acceleration mechanism of cosmic rays in shocks may be at work for neutrinos in supernova shocks when the latter are at densities greater than 10 to the 13th g/cu cm, at which the core material is opaque to neutrinos. A Monte Carlo approach to study this effect is employed, and the emerging neutrino power law spectra are presented. The increased energy acquired by the neutrinos may facilitate their detection in supernova explosions and provide information about the physics of collapse.
An investigation is conducted concerning the possibility that supernovae (SN), located in dense interstellar clouds, might become the sources of gamma ray lines. The SN progenitor, in such a case, has to be an O or B star so that its evolutionary lifetime is short, and an explosion inside the cloud is still possible. It is shown that, in principle, a measurement of the abundances in the ejecta is possible. Attention is given to the characteristics of a model, the expected luminosity of gamma-ray lines, and the study of specific numerical examples for testing the feasibility of the considered mechanism. On the basis of the obtained results, it is concluded that gamma-ray line production by collisional excitation in confined supernovae remnants may be quite important.
Consideration is given to imaging observations of supernova remnants (SNRs) obtained during the first year of the Einstein Observatory's operation. Inferences are drawn regarding models for stellar explosions, remnant evolution, neutron star formation and the interstellar medium. Because the X-ray emission traces the expanding shock boundary and dominates the radiative energy losses of an SNR over much of its lifetime, it can provide data on the possible collapsed remnants of the explosion, such as neutron stars and/or black holes. X-ray emission also allows a supernova shock to be used as a probe of interstellar medium structure. The imaging instrument aboard the Einstein satellite has been used to observe over 30 known Galactic remnants, and a similar number of objects in other galaxies, in the 0.15-4.5 keV band.
A general overview of supernova astronomy is presented, followed by a discussion of the relationship between SN and galactic cosmic rays. Pre-supernova evolution is traced to core collapse, explosion, and mass ejection. The two types of SN light curves are discussed in terms of their causes, and the different nucleosynthetic processes inside SNs are reviewed. Physical events in SN remnants are discussed. The three main connections between cosmic rays and SNs, the energy requirement, the acceleration mechanism, and the detailed composition of CR, are detailed.
The results of recent very long baseline interferometry of G127.11+0.54 at 10.65 GHz reveal a core dual 'jet' structure. The morphology and physical properties of the compact source are similar to those of SS 433. The combined data from various studies of this object suggest that G127.11+0.54 may be the stellar remnant of the supernova event which also produced the supernova remnant G127.1+0.5.