scholarly journals High Resolution X-ray Spectra of Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 205-211
Author(s):  
C. R. Canizares ◽  
P. F. Winkler ◽  
T. H. Markert ◽  
C. Berg
Keyword(s):  
Supernova Remnants ◽  
Abundance Ratio ◽  
Ionization Equilibrium ◽  
X Ray ◽  
Cygnus Loop ◽  
Doppler Shifts ◽  
Wide Range ◽  
Cas A ◽  
Einstein Observatory ◽  
Tycho’S Snr

We review results obtained with the Focal Plane Crystal Spectrometer (FPCS) on the Einstein Observatory. Clear evidence is found for departures from ionization equilibrium in the interior of Puppis A. This comes from the observed weakness of the forbidden lines relative to the resonance lines for the He - like triplets of O VII and Ne IX. However, it is shown that this departure from equilibrium does not alter our conclusion, based on previous FPCS results, that O and Ne are overabundant relative to Fe. The spectrum of N132D shows strong O VIII emission and very weak Fe emission, suggesting an even greater O/Fe abundance enhancement than in Puppis A. In the Cygnus Loop, the O to Ne abundance ratio is approximately solar; we have no information about Fe. The O VII triplet shows clear evidence for departures from ionization equilibrium in the Cygnus Loop. The spectrum of Tycho's SNR contains lines from ionization stages of Fe XVII through Fe XXIII and XXIV, indicating that a wide range of ionization conditions are present. Cas A and Kepler's SNR show relatively less emission from the higher ionization stages. For Tycho, we measured the strength of the strong Si XIII lines, and we find that a many-fold overabundance of Si relative to Fe is required regardless of the equilibrium state of the emitting plasma (confirming the Solid State Spectrometer results). On a separate topic, the completed analysis of X-ray Doppler shifts in Cas A suggests that the emitting material is concentrated in a ring that is inclined to the line of sight and is expanding at ~5000 km s−1.

scholarly journals Einstein Observatory Limits on Neutron Star Surface Temperatures

1987 ◽  
Vol 125 ◽  
pp. 457-457
Author(s):  
F.R. Harnden
Keyword(s):  
Star Formation ◽  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Remnants ◽  
Theoretical Models ◽  
X Ray ◽  
Star Models ◽  
Formation And Evolution ◽  
Star Surface ◽  
Einstein Observatory

For years the theoretical models of neutron star formation and evolution had remained largely unconstrained by observation. Following the Einstein X-ray Observatory surveys of supernova remnants and pulsars, however, strict temperature limits were placed on many putative neutron stars. The Einstein search for additional objects in the class of supernova remnants with embedded pulsars has increased the number of such objects by two. For the four objects in this class, the surface temperature limits (see Table 1) provide meaningful logically sound constraints on the neutron star models. For the future, however, still better X-ray observations are needed, both to increase the number of objects available for study and to refine the spatial and spectral capabilities of the X-ray measurements.

scholarly journals X-ray spectral variations over the Cygnus Loop and Puppis A supernova remnants

1980 ◽  
Vol 191 (4) ◽  
pp. 729-737 ◽  
Author(s):  
M. A. Kayat ◽  
D. P. Rolf ◽  
G. C. Smith ◽  
R. Willingale
Keyword(s):  
Supernova Remnants ◽  
X Ray ◽  
Cygnus Loop

scholarly journals Models for the Emission Line Spectra of Oxygen-rich Supernova Remnants

1987 ◽  
Vol 40 (6) ◽  
pp. 789 ◽  
Author(s):  
Michael A Dopita
Keyword(s):  
Supernova Remnants ◽  
Optical Emission ◽  
Theoretical Modelling ◽  
Optical Data ◽  
X Ray ◽  
Elemental Abundances ◽  
Current State ◽  
Enormous Amount ◽  
Degree Of Confidence ◽  
Cas A

The mechanism of excitation of the oxygen-rich class of young supernova remnants (SNRs), typified by the fast-moving knots of Cas A, is not currently understood. In this paper we review the available optical data and the current state of attempts at theoretical modelling. A new model is proposed which dramatically improves the fit of the theory with the observations for this class of SNRs. The model is of an X-ray driven R-type ionisation front precursor of a very fast shock. The peculiarities of the thermal balance in oxygen allow an enormous amount of superheating in the gas, which is first exposed to the X-ray ionising field, and the optical emission occurs in this superheated gas. The fit with observation is sufficiently good to give some degree of confidence that the mode of excitation of the plasma has at last been identified, and elemental abundances in four young oxygen-rich SNRs are derived.

scholarly journals Optical and UV Observations of Supernova Remnants

1996 ◽  
Vol 145 ◽  
pp. 381-389
Author(s):  
Robert A. Fesen
Keyword(s):  
Mass Loss ◽  
Proper Motion ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
Circumstellar Disk ◽  
Mantle Material ◽  
Cygnus Loop ◽  
Cas A ◽  
The Crab Nebula

Recent observations of the galactic supernova remnants the Crab Nebula, SN 1006, Cas A, and the Cygnus Loop are reviewed. New studies of the Crab Nebula suggest its progenitor may have had appreciable mass loss in the form of a circumstellar disk resulting in both a bipolar expansion and formation of the synchrotron ‘bays'. Unusually high proper motion knots near to and possibly directed away from the pulsar also have been reported. In the Cas A remnant, a NE jet of ejecta appears to be a plume of mantle material with expansion velocities up to 12000 km s-1 or nearly twice that seen in the main ejecta shell. HST observations of the sdOB star located behind SN 1006 indicate symmetrically expanding Fe II ejecta out to 8100 km s-1. Lastly, deep images of the Cygnus Loop reveal emission structures similar to those seen in 2D & 3D shocked cloud simulations.

scholarly journals Quasar Contribution to the X-Ray Background

1981 ◽  
Vol 94 ◽  
pp. 273-274
Author(s):  
Ajit Kembhavi ◽  
A. C. Fabian
Keyword(s):  
X Ray ◽  
Statistical Correlations ◽  
Wide Range ◽  
X Ray Background ◽  
Einstein Observatory ◽  
Insight Into

Recent observations by the Einstein Observatory have shown that a majority of known quasars are powerful X-ray emitters. The 107 objects observed as of Feb. 1980 (Zamorani et al. 1980) have X-ray, optical and radio luminosities scattered over a wide range. Until a large enough X-ray selected sample of quasars becomes available, it is necessary to study statistical correlations in the available sample, so that some insight into X-ray production may be obtained, and the contribution of quasars to the X-ray background estimated.

scholarly journals Non-Equilibrium Ionization X-ray Emission from Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 99-107
Author(s):  
J. Michael Shull
Keyword(s):  
Supernova Remnants ◽  
Heavy Element ◽  
Plasma Temperature ◽  
Supernova Explosion ◽  
Theoretical Models ◽  
Astrophysical Plasmas ◽  
Ionization Equilibrium ◽  
X Ray ◽  
Elemental Abundances ◽  
Stellar Nucleosynthesis

X-ray spectra of young supernova remnants (SNR's) are perhaps the most spectacular examples of hot, line-emitting astrophysical plasmas. Heated to temperatures of 1 to 10 keV and enriched with the heavy element products of stellar nucleosynthesis, the plasma inside these SNR's emits prodigiously in lines of 0, Ne, Mg, Si, S, Ar, Ca, and Fe. Theoretical models of this emission provide measures of the plasma temperature and density, elemental abundances, and the degree of approach to ionization equilibrium. Thus, astrophysicists are offered the opportunity to test their understanding of the supernova explosion, its interaction with the interstellar medium, and the nucleo-synthetic processes which enrich our galaxy with heavy elements.

Observations at 408 MHz of Supernova Remnants in the LMC

1971 ◽  
Vol 2 (1) ◽  
pp. 44-45 ◽  
Author(s):  
J. N. Clarke
Keyword(s):  
Supernova Remnants ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Independent Evidence ◽  
Cygnus Loop ◽  
Cas A ◽  
Thermal Sources

There are three non-thermal sources in the Large Magellanic Cloud which are recognized as supernova remnants. They are N49, N63A and N132D in Henize’s catalogue; a summary of their observing history is given by Westerlund and Mathewson (hereinafter referred to as ‘WM’). They are rather important to our knowledge of supernovae, as there are only four galactic supernova remnants (Cas A, the Crab, the Cygnus Loop and Vela) whose distances are known approximately from independent evidence. Since the distance to the LMC is well-known, the distance to sources in it is also known quite accurately.

scholarly journals X-Ray Spectroscopic Measurements of Non-Equilibrium Ionization in Supernova Remnants

1984 ◽  
Vol 86 ◽  
pp. 76-79
Author(s):  
T.H. Markert ◽  
C.R. Canizares ◽  
T. Pfafman ◽  
P. Vedder ◽  
P.F. Winkler ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
X Rays ◽  
Ionization Equilibrium ◽  
X Ray ◽  
Elemental Abundances ◽  
Ion Collisions ◽  
Ionization Structure ◽  
Cool Plasma ◽  
Collisional Ionization ◽  
Time Required

When a cool plasma is shock-heated to X-ray temperatures, the ionization structure does not attain its final, equilibrium value immmediately, but proceeds toward it through electron-ion collisions with a timescale τ ≡ net of order 1012 cm−3 sec. For supernova remnants (SNRs), where 0.1 ≤ ne ≤ 10 cm−3 typically, the time required to achieve collisional ionization equilibrium (CIE) can be greater than the age of the remnant. Even if the SNR is quite old, that part of the remnant which is emitting most of the X-rays may have been shocked relatively recently, so that the assumption of CIE may be inappropriate (see below).The question of ionization equilibrium is of great astrophysical importance in the study of SNRs because it affects the deduced values of their masses and elemental abundances (e.g. Shull 1982). Mass determinations are affected because underionized plasma generally has a much higher emissivity in soft X-rays than equilibrium plasma. Unless this is accounted for, the deduced value of the density and therefore of the mass, will be considerably overestimated.

scholarly journals The High Energy X-ray Spectra of Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 29-36
Author(s):  
Steven H. Pravdo ◽  
John J. Nugent
Keyword(s):  
Lower Energy ◽  
Supernova Remnants ◽  
High Energy ◽  
X Rays ◽  
Energy Data ◽  
X Ray ◽  
Ionization Structure ◽  
Continuum Contribution ◽  
Cas A ◽  
Ionization Nonequilibrium

We present the results of fitting an ionization nonequilibrium (NIE) model to the high energy (> 5 keV) X-ray spectra of the young supernova remnants Cas A and Tycho. As an additional constraint, we demand that the models simultaneously fit lower energy, higher resolution data. For Cas A, a single NIE component can not adequately reproduce the features for the entire X-ray spectrum because 1) the ionization structure of iron ions responsible for the K emission is inconsistent with that of the ions responsible for the lower energy lines, and 2) the flux of the highest energy X-rays is underestimated. The iron K line and the high energy continuum could arise from the same NIE component but the identification of this component with either the blast wave or the ejecta in the “standard” model is difficult. In Tycho, the high energy data rule out a class of models for the lower energy data which have too large a continuum contribution.

X-Ray Observations of Supernova Remnants from the Einstein Observatory

1980 ◽  
Vol 4 (1) ◽  
pp. 4-8 ◽  
Author(s):  
Ian R. Tuohy
Keyword(s):  
Supernova Remnants ◽  
X Ray ◽  
The Past ◽  
Optical Wavelengths ◽  
Einstein Observatory

The most extensive studies of supernova remnants (SNRs) in the past have taken place at radio and optical wavelengths.

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