scholarly journals Interstellar absorption of X-rays emitted by supernova remnants

1970 ◽  
Vol 37 ◽  
pp. 134-137
Author(s):  
P. Gorenstein ◽  
E. M. Kellogg ◽  
H. Gursky
Keyword(s):  
Supernova Remnants ◽  
Galactic Center ◽  
Crab Nebula ◽  
A Priori ◽  
Time Interval ◽  
Short Time Interval ◽  
X Rays ◽  
X Ray ◽  
The Galaxy ◽  
Cas A

An X-ray observation of the Cassiopeia Region by the ASE group from a sounding rocket on December 5, 1968, has resulted in the determination of locations for two sources that are precise to about 0.1 of a square degree. The positions of two well-known radio sources Cas A and SN 1572 (Tycho's Supernova), objects which are remnants of relatively recent galactic supernova, are consistent with these locations. Inasmuch as that region of the galaxy does not appear to contain nearly as large a concentration of objects as the galactic center, it is reasonable to make the identification between the X-ray sources and the supernova remnants on the basis of there being a small a priori probability of having an accidental coincidence within 0.1 square degrees. Cas A is almost certainly the same source as Cas XR-1 which the NRL group saw in an earlier survey [1]. During the December flight the Crab nebula was also observed for a short time interval.

scholarly journals Hard Cosmic X-Ray Sources

1973 ◽  
Vol 55 ◽  
pp. 51-73 ◽  
Author(s):  
L. E. Peterson
Keyword(s):  
Supernova Remnants ◽  
Galactic Center ◽  
Galactic Plane ◽  
Crab Nebula ◽  
X Rays ◽  
X Ray ◽  
Sky Survey ◽  
Upper Limits ◽  
Observational Status ◽  
The Crab Nebula

A review of the observational status of X-ray sources detected in the 20 ⋍ 500 keV range is presented. Of the approximately 115 sources listed in the March 1972 edition of the UHURU 2–6 keV sky survey catalog, about 15 sources have been studied in hard X-rays. Most of the data have been obtained from balloons, although the OSO-3, and more recently the OSO-7, have contributed. With the exception of CEN A, the SMC, and possibly M-87, all the sources detected at higher energies are galactic and heavily concentrated in the galactic plane. The Crab Nebula has been measured to about 500 keV in continuous emission and a component at the ⋍ 33 ms pulsar period comprising about 20% of the total emission has been detected to ∼10 MeV. Objects such as SCO-1 and CYG-2 are characterized by an exponential spectrum, which varies over a 10 min. time scale about a factor of two, and a flatter spectrum extending to above 40 keV which exhibits independent variability. Objects such as CYG-1 and possibly CYG-3 have a multi-component power law spectrum extending to over 100 keV, and may vary many factors over a period of weeks. Other sources generally not yet identified with optical or radio candidates, located in the Galactic Center and the Centaurus/Crux region also show considerable variability, and in one case may have been detected to nearly 500 keV. Only upper limits at about 2 × 10−4 photon (cm2 s keV)−1 in the 20–50 keV range exist for most supernova remnants and extragalactic sources.

scholarly journals High energy cosmic photons and neutrinos

1965 ◽  
Vol 23 ◽  
pp. 195-225
Author(s):  
R. J. Gould ◽  
G. R. Burbidge
Keyword(s):  
Supernova Remnants ◽  
Crab Nebula ◽  
Meson Production ◽  
Cosmic Ray ◽  
High Energy ◽  
Relativistic Electrons ◽  
X Ray ◽  
Hard Radiation ◽  
The Galaxy ◽  
The Crab Nebula

This review concentrates primarily on the problem of interpreting the recent X-ray and γ-ray observations of celestial sources. The expected fluxes of hard radiation from various processes are estimated (when possible) and are compared with the observations. We compute the synchrotron, bremsstrahlung, and (inverse) Compton spectra originating from relativistic electrons produced (via meson production) in the galaxy and intergalactic medium by cosmic ray nuclear collisions; the spectra from π°-decay are also computed. Neutron stars, stellar coronae, and supernova remnants are reviewed as possible X-ray sources. Special consideration is given to the processes in the Crab Nebula. Extragalactic objects as discrete sources of energetic photons are considered on the basis of energy requirements; special emphasis is given to the strong radio sources and the possibility of the emission of hard radiation during their formation. The problem of the detection of cosmic neutrinos is reviewed.As yet, no definite process can be identified with any of the observed fluxes of hard radiation, although a number of relevant conclusions can be drawn on the basis of the available preliminary observational results. In particular, some cosmogonical theories can be tested.

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 A balloon-borne X-ray survey of the central region of the galaxy

1968 ◽  
Vol 46 (10) ◽  
pp. S444-S447 ◽  
Author(s):  
Elihu Boldt ◽  
Henry Doong ◽  
Peter Serlemitsos ◽  
Guenter Riegler
Keyword(s):  
Central Region ◽  
Proportional Counter ◽  
Galactic Center ◽  
Galactic Plane ◽  
Cesium Iodide ◽  
X Rays ◽  
Scintillation Crystal ◽  
X Ray ◽  
Gas Proportional Counter ◽  
The Galaxy

A balloon-borne X-ray survey of the galactic plane in the region of the galactic center was made from Australia during December 1966. The photon events recorded by a detector composed of a krypton gas proportional counter and a cesium iodide scintillation crystal are used to determine the spectrum of hard X-rays from the vicinity of Sgr XR-1.

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 A Catalogue of Galactic Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 597-604 ◽  
Author(s):  
Sidney van den Bergh
Keyword(s):  
Supernova Remnants ◽  
X Rays ◽  
True Nature ◽  
X Ray ◽  
The Galaxy ◽  
Optical Wavelengths ◽  
Optical Identifications

At this conference results have been presented on a number of individual galactic supernova remnants, but many others remain unstudied. It therefore seemed worthwhile to present a catalogue of all presently known SNR's in the Galaxy. Objects of which the true nature is not yet well established have, as far as possible, been omitted. Remnants which have been detected at optical wavelengths are marked by an asterisk in Table 1. Data on the optical identifications are from van den Bergh (1978), supplemented by recent results of Zealey, Elliot and Malin (1979), Reich, Kallas and Steube (1979), Downes, Pauls and Salter (1980), van den Bergh (1981) and Reich and Braunsfurth (1981). Also marked in the table are supernova remnants that have been detected in x-rays. These x-ray identifications are from miscellaneous sources.

scholarly journals Optical and Radio Information

1968 ◽  
Vol 1 ◽  
pp. 206-209
Author(s):  
Hugh M. Johnson
Keyword(s):  
Cross Sections ◽  
Supernova Remnants ◽  
Galactic Plane ◽  
Optical Data ◽  
X Rays ◽  
Interstellar Gas ◽  
X Ray ◽  
The Galaxy ◽  
Ionization Cross Sections ◽  
Optical Astronomy

The six or eight optically identified X-ray sources comprise starlike objects and extended supernova remnants in the Galaxy, well as as a radio galaxy and a quasar. Both X-ray and radiofrequency radiation penetrate the entire galactic plane, but only two or three galactic radio sources have been identified with X-ray sources. This has led Hayakawa et al. to postulate that detectable X-ray sources are not farther than 1 kpc. However, other studies suggest that there is a cluster of a few intrinsically bright sources actually near the galactic nucleus and a scattering of weaker sources near the sun.The distances of X-ray sources can be estimated from extinction by interstellar gas or intergalactic gas on spectra above 10 Å, but the method ultimately depends on the radio and optical data of the gas. Conversely, interstellar densities of certain elements with large photo-ionization cross-sections may be determined from the absorption of X-rays, after calibration of source distances by the methods of optical astronomy.

scholarly journals X-ray Observations of Crab-Like Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 321-328
Author(s):  
R. H. Becker
Keyword(s):  
Spatial Distribution ◽  
Kinetic Energy ◽  
Radio Emission ◽  
Supernova Remnants ◽  
Galactic Plane ◽  
Crab Nebula ◽  
Radio Spectrum ◽  
X Rays ◽  
X Ray ◽  
Evolutionary Connection

On the basis of extensive radio surveys of the galactic plane, approximately 140 sources of diffuse radio emission have been classified as supernova remnants (SNR). Using spectral index and spatial distribution as the primary selection criteria, these have been subdivided into two groups, “shell” and “Crab-like”. In each case, the radio emission is assumed to be of non-thermal origin. The two distinct morphologies arise from two distinct energy sources. For shell remnants, the energy is drawn from the reservoir of kinetic energy in the expanding shock front; in Crab-like remnants, the energy is drawn from the rotational kinetic energy of a central stellar remnant.These two classes of remnants differ significantly in their x-ray emission. With few exceptions, radio shell remnants emit thermal x-rays from shock heated gas which is itself distributed in a shell. Crab-like sources (as defined by their radio properties) emit synchrotron x-rays in a centrally-peaked spatial distribution. Presumably, the x-ray emission from these objects is an extension of the radio spectrum. Crab-like sources have a high probability of containing a compact (unresolved) source of x-ray emission which in analogy to the Crab Nebula, is identified as the central stellar remnant.The general absence of either compact x-ray sources or Crab-like diffuse nebulae within shell sources indicates that active pulsars are not usually formed in SN events which eventually form shell sources. However, there are several examples of remnants which share both shell and Crab-like characteristics so we cannot rule out an evolutionary connection between these two classes of SNR.

Some recent observations of supernova remnants emitting X-rays

1979 ◽  
Vol 366 (1726) ◽  
pp. 311-327
Keyword(s):  
Supernova Remnants ◽  
Supernova Remnant ◽  
X Rays ◽  
Coronal Line ◽  
Crystal Spectrometer ◽  
X Ray ◽  
Cygnus Loop ◽  
The Galaxy ◽  
Two Distinct Temperatures ◽  
Line Observation

There are currently believed to be 13 X-ray sources which can be fairly confidently identified with galactic supernova remnants. All of these sources are thought to be at reasonably small distances, thus supporting the view that absorption in the interstellar medium prevents us from seeing the more distant galactic remnants with the level of sensitivity currently available from soft X-ray instrumentation. Of the older remnants, the Cygnus Loop and Puppis-A are discussed in the light of recent observations. Several mapping experiments show that the Cygnus Loop exhibits a shell-like structure in X-rays, though with considerable fine structure. From these experiments, it is still not clear how uniform is the temperature over the X-ray emitting region. In addition, results from a crystal spectrometer are described which imply that the temperature may be higher than had been previously determined from proportional counter observations. Results from observations of Puppis-A are presented. These imply that two distinct temperatures exist in this source. It is argued that this may represent the interaction of the expanding shock front with a relatively dense interstellar cloud. The sources W44 and γ -Cygni supernova remnant are discussed and it is suggested that these may now be regarded as members of the class of confirmed X-ray emitting supernova remnants. Finally, an optical coronal line observation of the remnant N49 in the L. M. C. is considered, and it is suggested that this source is a likely candidate to be detected as the first X-ray emitting supernova remnant outside the galaxy.

scholarly journals Physical Processes and Parameters in the Magnetosphere of NP 0532

1971 ◽  
Vol 46 ◽  
pp. 394-406
Author(s):  
F. Pacini
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
General Relation ◽  
Energy Generation ◽  
Main Pulse ◽  
Physical Processes ◽  
X Ray ◽  
The Crab Nebula

The Crab Nebula pulsar conforms to the model of a rotating magnetised neutron star in the rate of energy generation and the exponent of the rotation law.It is suggested that the main pulse is due to electrons and the precursor to protons. Both must radiate in coherent bunches. Optical and X-ray radiation is by the synchrotron process.The wisps observed in the Nebula may represent the release of an instability storing about 1043 erg and 1047–48 particles.Finally, some considerations are made about the general relation between supernova remnants and rotating neutron stars.

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