scholarly journals Nonstationary Phenomena in the Radiation of Young Supernova Remnants

1987 ◽  
Vol 40 (6) ◽  
pp. 801 ◽  
Author(s):  
VP Ivanov ◽  
KS Stankevich
Keyword(s):  
Radio Emission ◽  
Flux Density ◽  
Spectral Index ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
Adiabatic Expansion ◽  
Cassiopeia A ◽  
Average Decrease ◽  
Tycho Brahe ◽  
The Crab Nebula

The time variation of the radio emission from the supernova remnants Cassiopeia A, the Crab Nebula and Tycho Brahe (SN 1572) is investigated. There is a frequency dependence on the rate of decrease in the flux density of Cassiopeia A for the period 1957 to 1984. The (positive) spectral index has a secular decrease and also, for frequencies above 320 MHz, slight oscillations with a six-year period. The radio emission from the Crab Nebula was constant from 1953 to 1975 but has since decreased accompanied by a change in spectral index. The average decrease of the flux density of SN 1572 from 1963 to 1983 was 0�52% per year, close to the value predicted for adiabatic expansion.

scholarly journals Peculiar Differences in Radio and X-ray Synchrotron Radiation from Pulsar Wind Nebulae

2004 ◽  
Vol 218 ◽  
pp. 221-224
Author(s):  
John R. Dickel ◽  
Shiya Wang
Keyword(s):  
Synchrotron Radiation ◽  
Radio Emission ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
Pulsar Wind Nebulae ◽  
X Ray ◽  
Pulsar Wind ◽  
The Crab Nebula

Several Crab-type supernova remnants appear to have very bright non-thermal X-ray cores just around the pulsar or expected pulsar. This X-ray brightness is often not matched by a corresponding increase in radio emission. The best example of this phenomenon is in N157B in the LMC. G21.5−0.9 and possibly 3C 58 also show it while the Crab Nebula and 0540−69.3 do not. Some method to enhance the higher energy particles must be present in these objects.

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 The radio sources in the Cygnus loop and IC443

1959 ◽  
Vol 9 ◽  
pp. 323-327 ◽  
Author(s):  
E. Margaret Burbidge ◽  
G. R. Burbidge
Keyword(s):  
Synchrotron Radiation ◽  
Radio Emission ◽  
Strong Evidence ◽  
Crab Nebula ◽  
Radio Sources ◽  
Cassiopeia A ◽  
Cygnus Loop ◽  
Physical Conditions ◽  
Nonthermal Radio ◽  
The Crab Nebula

Within our Galaxy there are a number of nonthermal sources of radio emission. In the last few years a considerable amount of data has been collected about some of these sources, in particular the Crab nebula and the Cassiopeia A source. There is strong evidence now to suggest that all of the nonthermal radio sources emit by synchrotron radiation, or acceleration radiation as we shall describe it here. In this paper we want to discuss the physical conditions in two objects, the Cygnus loop and IC 443.

Studies of the X-ray emission from supernova remnants

1974 ◽  
Vol 340 (1623) ◽  
pp. 423-437
Keyword(s):  
Supernova Remnants ◽  
Column Density ◽  
Supernova Remnant ◽  
Crab Nebula ◽  
Lower Intensity ◽  
X Ray ◽  
Cassiopeia A ◽  
Cygnus Loop ◽  
A Value ◽  
The Crab Nebula

Supernova remnants are now recognized as a class of soft X-ray emitting-objects. The evolution of a remnant’s X-ray emission is discussed and a number of possible X-ray emission mechanisms are described. The spectrum of the Crab Nebula has been studied with Copernicus. The data have been used to derive a value of the gas column density of the interstellar medium. The X-ray structure and spectrum of the remnant Cassiopeia. A have been investigated and the results are presented. A high resolution X-ray map of the Puppis A supernova remnant has been obtained and the interpretation of the X-ray structure is discussed. X-ray emission has been detected from the pulsar PSR 08 33-45. This observation is compared with data obtained from the Uhuru satellite in order to derive the gas column density to the source. Weak soft X-ray emission has been detected from the Cygnus Loop in the regions expected but a t a lower intensity – a search for regions of higher intensity is continuing. A programme to identify known radio remnants as X-ray emitters is in progress and the results obtained so far are reported.

scholarly journals A Newly-Recognised Galactic Supernova Remnant with Shell-Type and Filled-Centre Features

1988 ◽  
Vol 101 ◽  
pp. 347-350
Author(s):  
Peter J. Barnes ◽  
A.J. Turtle
Keyword(s):  
Spectral Index ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Crab Nebula ◽  
Dual Nature ◽  
Valuable Addition ◽  
Shell Type ◽  
The Crab Nebula ◽  
Galactic Object

While the number of galactic supernova remnants (SNRs) now known is fairly large (>150), the subset among these that are known to resemble the Crab Nebula is still distressingly small, about 15 or so (Green, 1984). Thus any object that can be unambiguously included in this exclusive club forms a valuable addition to our knowledge of this class. We report here observations of a newly recognised nonthermal galactic object, G18.94-l.06, having all the hallmarks of the classical shell-type SNRs, while also appearing to have a filled-centre component located inside the shell. Among the known Crab-like remnants, about one third show this dual nature (Green, 1984). This diagnosis of G18.94-1.06 is supported mainly by the variations in spectral index α (Sν∝ να) across the source, as seen between the two observation frequencies, 408 MHz and 5.0 GHz.

scholarly journals Radio Emission from Supernova Remnants

1971 ◽  
Vol 46 ◽  
pp. 248-262
Author(s):  
D. K. Milne
Keyword(s):  
Radio Emission ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
The Other ◽  
The Galaxy ◽  
The Crab Nebula ◽  
Thermal Sources

Observations of the radio emission from supernova remnants are reviewed with emphasis on the dissimilarity between the Crab Nebula and the other remnants. From this we conclude that there may be several non-thermal sources in the Galaxy with the same centrally filled structure as the Crab. These are, however, more evolved, and clearly there is no other source of the same age and type as the Crab Nebula.

scholarly journals The Electromagnetic Spectrum of the Crab Nebula

1971 ◽  
Vol 46 ◽  
pp. 22-31 ◽  
Author(s):  
J. E. Baldwin
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Crab Nebula ◽  
Electromagnetic Spectrum ◽  
Optical Range ◽  
X Ray ◽  
Radio Data ◽  
A Value ◽  
The Crab Nebula

I shall discuss observations of the spectrum of the integrated emission from the Crab Nebula. The radio data with accurate calibrations lead to a flux density spectral index of −0.26. Discrepancies in the published fluxes at millimetre wavelengths can be resolved if appropriate angular dimensions are used. In the optical range the spectral index has increased to a value of −0.9 if 1m.0 of absorption is used. At X-ray wavelengths the spectral index has increased further to −1.2.

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