Polarized Brightness Distribution Over Cassiopeia a, the Crab Nebula, and Cygnus a at 1.55 CM Wavelength

1968 ◽  
Vol 151 ◽  
pp. 53 ◽  
Author(s):  
C. H. Mayer ◽  
J. P. Hollinger
Keyword(s):  
Crab Nebula ◽  
Brightness Distribution ◽  
Cassiopeia A ◽  
Cygnus A ◽  
The Crab Nebula

scholarly journals The structure of the Cassiopeia A and Cygnus A radio sources measured at 127 Mc/s and 3000 Mc/s

1959 ◽  
Vol 9 ◽  
pp. 309-314
Author(s):  
R. C. Jennison
Keyword(s):  
Position Angle ◽  
Brightness Distribution ◽  
Radio Sources ◽  
Cassiopeia A ◽  
The Third ◽  
Cygnus A ◽  
Main Component ◽  
Main Region

The brightness distribution across the Cassiopeia A source in position angle 90 degrees consists of a primary region of emission 4.1 minutes of arc in width, with a much fainter extension offset from the main region of emission and having a brightness of only 10 per cent of that of the main component. Measurements were made up to the third maximum of the transform (2160 λ), and the position of the first zero was determined at 840 λ.

Coronal Broadening of the Crab Nebula 1969-71: Interpretation

1972 ◽  
Vol 2 (2) ◽  
pp. 86-88 ◽  
Author(s):  
P. A. Dennison ◽  
R. G. Blesing
Keyword(s):  
Power Spectrum ◽  
Crab Nebula ◽  
Preceding Paper ◽  
Theoretical Models ◽  
Brightness Distribution ◽  
Two Dimensional ◽  
Scattering Process ◽  
Angular Power Spectrum ◽  
Basic Parameters ◽  
The Crab Nebula

In the preceding paper, observations of the coronal broadening of the Crab Nebula during 1969-71 were described. The basic parameters, radial and tangential broadening, and their relation to previous work were discussed. Whereas previous observations have utilized two or three interferometers only, so that the degree of broadening along any particular axis could only be obtained under the assumption of a particular form (e.g. Gaussian) for the angular power spectrum, the present work has enabled complete sampling of the two-dimensional brightness distribution of the broadened source. It is therefore possible, and of considerable interest, to compare the observed distributions to those computed on the basis of various theoretical models for the scattering process.

scholarly journals Synchrotron Thermal Instabilities and Radio Filaments in the Lobes of Cygnus A

1989 ◽  
Vol 8 ◽  
pp. 417-422
Author(s):  
G. Bodo ◽  
A. Ferrari ◽  
S. Massaglia ◽  
E. Trussoni
Keyword(s):  
Magnetic Field ◽  
Thermal Instability ◽  
Crab Nebula ◽  
Relativistic Electrons ◽  
Synchrotron Emission ◽  
Cygnus A ◽  
The Crab Nebula ◽  
The Magnetic Field

Recent VLA observations of the lobes of Cygnus A exhibit complex “filamentary” structures, with typical scale width ~ 1 arcsec (Dreher, Carilli and Perley, 1987, Perley, 1987). The filaments appear aligned with the magnetic field, as results from polarization measures, suggesting that the field may play a fundamental role in the process of their formation.We propose a mechanism for the possible formation of these filaments based upon a thermal instability connected with synchrotron emission from relativistic electrons. This type of instability was studied by Simon and Axford (1967), who discussed it in connection with the Crab Nebula filaments, and by Eilek and Caroff (1979), who generalized the previous study for application to quasar atmospheres.

The Fortieth Anniversary of Extragalactic Radio Astronomy: Radiophysics in Exile

1990 ◽  
Vol 8 (04) ◽  
pp. 381-383 ◽  
Author(s):  
J. G. Bolton
Keyword(s):  
Radio Astronomy ◽  
Crab Nebula ◽  
Low Frequency ◽  
Early Years ◽  
Owens Valley ◽  
Detection Range ◽  
Staff Members ◽  
Cygnus A ◽  
The Galaxy ◽  
The Crab Nebula

In 1931 Karl Jansky established that radio noise was associated with our own galaxy–the Milky Way. For a decade and a half there was little follow-up; those of us who were associated with low frequency radar during the war regarded it as a nuisance which could limit the detection range of enemy aircraft. Grote Reber was the first to make a detailed but fairly low resolution map of the radiation from the galaxy showing, for the first time, some detailed structure. The event which we celebrate today occurred when Gordon Stanley, Bruce Slee and I showed that three of the discrete sources that we had discovered could be identified with visual objects. One was with the Crab Nebula, a supernova remnant within our own galaxy and the other two with galaxies, far beyond our own system, in the constellations of Virgo and Centaurus. Thus began extragalactic radio astronomy. In 1982 at the Noosa meeting of the ASA, I gave an account of those early years, later to be published in the ASA Proceedings. As I don’t wish to repeat myself, I propose to speak on my involvement in a later development which was to extend the observable scale of the universe to look-back times as great as the age of the oldest stars in our own system. The first important step was Graham Smith’s identification of Cygnus A with a galaxy that was much fainter than our two. The spectrum by Minkowski revealed an instrinsically highly-luminous galaxy with strong emission lines and opened up the possibility of discovering similar objects at significantly greater distance. This was achieved nine years later with the building of the Owens Valley Observatory and my title of ‘Radiophysics in Exile’ comes from the fact the observatory owed its existence and early successes very largely to past and future staff members of Radiophysics. They were, in order of appearance, J. G. Bolton, G. J. Stanley, K. C. Westfold, J. A. Roberts, V. Radhakrishnan, D. Morris and K. I. Kellermann. Some still bear . the scars–Westfold left the tip of one index finger in the Owens Valley!

scholarly journals The Common Properties of Plerions and Active Galactic Nuclei

1981 ◽  
Vol 94 ◽  
pp. 165-166
Author(s):  
N. Panagia ◽  
K. W. Weiler
Keyword(s):  
Supernova Remnants ◽  
Crab Nebula ◽  
Spectral Characteristics ◽  
Radio Spectrum ◽  
Brightness Distribution ◽  
Relativistic Electrons ◽  
Object A ◽  
Linearly Polarized ◽  
Bona Fide ◽  
The Crab Nebula

Plerions, i.e. supernova remnants resembling the Crab Nebula, are characterized at radio wavelengths by having: 1) a centrally peaked brightness distribution, 2) flat radio spectrum (α > −0.3, Sν να), 3) high linear polarization, and 4) a highly ordered magnetic field. At higher frequencies (1011–1013 Hz depending upon the age) the spectrum turns over and attains a slope of α ~ −1. In particular, for the Crab Nebula the turnover frequency occurs at νc ~ 3×1012 Hz (cf. Fig. 1). Moreover, the optical spectrum displays a slope of −0.9 and the radiation is linearly polarized. Nonthermal emission is also detected in the X-ray and γ-ray domains (Fig.1). Similar spectral characteristics are found for other bona fide plerions. As discussed by Weiler and Panagia (1980), the plerion phenomenon is determined by the presence of a highly energetic and active central object (a fast spinning neutron star) which is able to both accelerate and inject continuously relativistic electrons into the remnant with a typically flat energy distribution roughly proportional to E−1.

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.

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