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 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 Aluminium incorporation in polar, semi- and non-polar AlGaN layers: a comparative study of x-ray diffraction and optical properties

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Duc V. Dinh ◽  
Nan Hu ◽  
Yoshio Honda ◽  
Hiroshi Amano ◽  
Markus Pristovsek
Keyword(s):  
Room Temperature ◽  
Optical Emission ◽  
Vapour Phase ◽  
Optical Data ◽  
Bandgap Energy ◽  
X Ray Diffraction ◽  
Vapour Phase Epitaxy ◽  
X Ray ◽  
Metal Organic ◽  
Organic Vapour

Abstract Growth of AlxGa1−xN layers (0 ≤ x ≤ 1) simultaneously on polar (0001), semipolar ($$10\bar{{\rm{1}}}$$ 10 1 ¯ 3) and ($$11\bar{{\rm{2}}}2$$ 11 2 ¯ 2 ), as well as nonpolar ($$10\bar{{\rm{1}}}0$$ 10 1 ¯ 0 ) and ($$11\bar{{\rm{2}}}0$$ 11 2 ¯ 0 ) AlN templates, which were grown on planar sapphire substrates, has been investigated by metal-organic vapour phase epitaxy. By taking into account anisotropic in-plane strain of semi- and non-polar layers, their aluminium incorporation has been determined by x-ray diffraction analysis. Optical emission energy of the layers was obtained from room-temperature photoluminescence spectra, and their effective bandgap energy was estimated from room-temperature pseudo-dielectric functions. Both x-ray diffraction and optical data consistently show that aluminium incorporation is comparable on the polar, semi- and non-polar planes.

Mixed-morphology supernova remnants: the case of SNR 0520–69.4 in the Large Magellanic Cloud

2020 ◽  
Vol 499 (3) ◽  
pp. 4213-4222
Author(s):  
I Ramírez-Ballinas ◽  
J Reyes-Iturbide ◽  
P Ambrocio-Cruz ◽  
R Gabbasov ◽  
M Rosado
Keyword(s):  
Supernova Remnants ◽  
Plasma Temperature ◽  
Optical Emission ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Physical Parameters ◽  
X Ray ◽  
Hot Plasma ◽  
Observatory Data ◽  
Fabry Perot

ABSTRACT We present observations in X-ray and optical emission of the supernova remnant (SNR) 0520–69.4 in the Large Magellanic Cloud. Using XMM–Newton observatory data, we produced images of the diffuse X-ray emission and spectra to obtain the X-ray parameters, such as luminosity and temperature, of hot plasma in the SNR. Diffuse X-ray emission with filled-centre morphology goes beyond the Hα region, suggesting that the hot gas escapes through the pores of the Hα shell. We fitted a model that has a plasma temperature of 1.1 × 107 K for an X-ray thermal luminosity of 3.3 × 1035 erg s−1. However, from Hα and [O iii] Fabry–Perot observations obtained with the Marseille Hα Survey of the Magellanic Clouds and the Milky Way at La Silla, European Southern Observatory, we are able to obtain physical parameters such as the velocity of the shock induced in the cloudlets emitting at optical wavelengths and the electron density of this gas. With the parameters described above, we test the model proposed by White & Long (1991, ApJ, 373, 543) for explaining the mixed-morphology observed.

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.

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.

scholarly journals Unveiling pure-metal ejecta X-ray emission in supernova remnants through their radiative recombination continuum

2020 ◽  
Vol 638 ◽  
pp. A101 ◽  
Author(s):  
Emanuele Greco ◽  
Jacco Vink ◽  
Marco Miceli ◽  
Salvatore Orlando ◽  
Vladimir Domček ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Spectral Resolution ◽  
Supernova Remnants ◽  
Radiative Recombination ◽  
Spectral Feature ◽  
Pure Metal ◽  
Chemical Abundances ◽  
X Ray ◽  
Cas A ◽  
Ccd Detectors

Context. Spectral analysis of X-ray emission from ejecta in supernova remnants (SNRs) is hampered by the low spectral resolution of CCD detectors, which typically creates a degeneracy between the best-fit values of chemical abundances and the plasma emission measure. The combined contribution of shocked ambient medium and ejecta to the emerging X-ray emission further complicates the determination of the ejecta mass and chemical composition. This degeneracy leads to big uncertainties in mass estimates and can introduce a bias in the comparison between the ejecta chemical composition derived from the observations and the yields predicted by explosive nucleosynthesis models. Aims. We explore the capabilities of present and future spectral instruments with the aim of identifying a spectral feature that may allow us to discriminate between metal-rich and pure-metal plasmas in X-ray spectra of SNRs. Methods. We studied the behavior of the most common X-ray emission processes of an optically thin plasma in the high-abundance regime. We investigated spectral features of bremsstrahlung, radiative recombination continua (RRC), and line emission, by exploring a wide range of chemical abundances, plasma temperatures, and ionization parameters. We then synthesized X-ray spectra from a state-of-the-art 3D hydrodynamic simulation of Cas A, by using the response matrix from the Chandra ACIS-S charged-coupled device detector and that of the XRISM/Resolve X-ray calorimeter spectrometer. Results. We found that a bright RRC shows up when the plasma is made of pure-metal ejecta, and a high spectral resolution is needed to actually identify this ejecta signature. We tested and verified the applicability of our novel diagnostic tool and we propose a promising target for the future detection of such spectral feature: the southeastern Fe-rich clump of Cas A. Conclusions. While there is no way to unambiguously reveal pure-metal ejecta emission with CCD detectors, X-ray calorimeters will be able to pinpoint the presence of pure-metal RRC and to recover correctly absolute mass and the chemical composition of the ejecta, opening a new window on the link between progenitor star, supernova and SNRs.

scholarly journals A compact X-ray emitting binary in likely association with 4FGL J0935.3+0901

2020 ◽  
Vol 493 (4) ◽  
pp. 4845-4851 ◽  
Author(s):  
Zhongxiang Wang ◽  
Yi Xing ◽  
Jujia Zhang ◽  
Konstantina Boutsia ◽  
Gege Wang ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Optical Emission ◽  
Emission Lines ◽  
Large Area ◽  
Time Resolved ◽  
X Ray ◽  
Current State ◽  
Low Mass ◽  
Γ Ray ◽  
Error Circle

ABSTRACT 4FGL J0935.3+0901 is a γ-ray source detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope. We have conducted detailed analysis of the LAT data for this source and multiwavelength studies of the source field. Its γ-ray emission can be described with a power law (Γ = 2.0 ± 0.2) with an exponential cut-off (Ec = 2.9 ± 1.6 GeV), while the flux shows significant long-term variations. From analysis of archival Neil Gehrels Swift Observatory X-Ray Telescope data, we find only one X-ray source in the LAT’s 2σ error region. Within a $3.7\,{\rm arcsec}$ radius error circle of the X-ray source, there is only one optical object down to r′ ∼ 23 mag. Time-resolved photometry of the optical object indicates a likely 2.5 h periodic modulation, while its spectrum shows double-peaked hydrogen and helium emission lines (similar to those seen in accretion discs in low-mass X-ray binaries). Combining these results, we conclude that we have discovered a compact X-ray emitting binary in likely association with 4FGL J0935.3+0901, i.e. a millisecond pulsar (MSP) binary. We discuss the implication of the optical spectral features: this binary could be a transitional MSP system at a subluminous disc state, although the other possibility, the binary in a rotation-powered state showing the optical emission lines due to intrabinary interaction processes, cannot be excluded. Further observational studies will help to determine detailed properties of this candidate MSP binary and thus clarify its current state.

scholarly journals The Secular Behavior of X-Ray and Radio Emission from Supernova Remnants

1971 ◽  
Vol 46 ◽  
pp. 268-272
Author(s):  
Wallace H. Tucker
Keyword(s):  
Radio Emission ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
X Ray ◽  
Cas A ◽  
The Crab Nebula ◽  
Continuous Injection

Continuous injection models for the secular behavior of the radio and X-ray emission from supernova remnants are examined and compared with the observations. Among other things, it is concluded that (1) continuous injection probably occurs for at least 10 yr in every case and about 1000 yr in most supernova remnants, in which case the supernova remnants 3C392, W28, Pup A and IC443 should produce 1–10 keV X-ray fluxes ≈ 10-10 ergs/cm2-sec, and (2) the X-ray sources in the Crab Nebula, Cas A and Tycho can be explained in terms of a model wherein continuous injection occurs for 300 yr for the Crab Nebula, much less than 250 yr for Cas A and much longer than 400 yr for Tycho. Finally, it is shown that if Tycho and Cas A contain an X-ray star such as NP 0532, it is quite possible that the X-ray emission from those sources is predominantly due to the X-ray star.

scholarly journals X-ray and Optical Properties of Radio Jets

2005 ◽  
Vol 13 ◽  
pp. 685-691 ◽  
Author(s):  
D.M. Worrall
Keyword(s):  
Optical Properties ◽  
Spectroscopic Data ◽  
Optical Data ◽  
High Quality ◽  
X Ray ◽  
Radio Jets ◽  
Current State ◽  
Quality Imaging

AbstractOver the last few years the high-quality imaging and spectroscopic data from Chandra and XMM-Newton have added greatly to our knowledge of the physics of radio jets. Supported by optical data, we are now able to understand much about jet energetics. Here I review the current state of knowledge.

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