scholarly journals The Lunar Occultation Of The Crab Nebula Observed At Parkes On June 21, 1963

1966 ◽  
Vol 19 (3) ◽  
pp. 409 ◽  
Keyword(s):  
Spectral Index ◽  
Linear Polarization ◽  
Radio Occultation ◽  
Crab Nebula ◽  
Frequency Range ◽  
Lunar Occultation ◽  
Central Regions ◽  
Optical Continuum ◽  
Optical Brightness ◽  
The Crab Nebula

Measurements of the intensity and percentage linear polarization of the Crab nebula radiation at 404 and 1420 Mc/s were made during the partial occultation of .June 21, 1963. The radio occultation curves are similar in shape to that calculated from the isophotes of the optical continuum and show the same principal features. However, the ratio of radio to optical brightness varies in a systematic way across the source, the ratio being greater at the edges than in the central regions. This steepening of the spectral index towards the outer edges continues in the radio frequency range from 1420 to 404 Mc/s. The 1420 Mc/s linear polarization is stronger in the inner areas (2,5%) than in the outer areas (< 1%) of the source.

Radio Observations of the Crab Nebula during a Lunar Occultation

Nature ◽  
1964 ◽  
Vol 203 (4941) ◽  
pp. 171-173 ◽  
Author(s):  
B. H. ANDREW ◽  
N. J. B. A. BRANSON ◽  
D. WILLS
Keyword(s):  
Crab Nebula ◽  
Radio Observations ◽  
Lunar Occultation ◽  
The Crab Nebula

Lunar occultation of the hard X-ray source in the Crab Nebula

Nature ◽  
1975 ◽  
Vol 255 (5508) ◽  
pp. 465-466 ◽  
Author(s):  
Y. FUKADA ◽  
S. HAYAKAWA ◽  
I. KASAHARA ◽  
F. MAKINO ◽  
Y. TANAKA ◽  
...  
Keyword(s):  
Crab Nebula ◽  
X Ray ◽  
Lunar Occultation ◽  
The Crab Nebula

scholarly journals Diffusion and advection model for particle transport in young pulsar wind nebulae

2012 ◽  
Vol 8 (S291) ◽  
pp. 265-268
Author(s):  
Xiaping Tang ◽  
Roger A. Chevalier
Keyword(s):  
Spectral Index ◽  
Particle Transport ◽  
Crab Nebula ◽  
Outer Boundary ◽  
Outer Part ◽  
Pulsar Wind Nebulae ◽  
Pure Diffusion ◽  
Pulsar Wind ◽  
Kink Instability ◽  
The Crab Nebula

AbstractThe magnetohydrodynamic (MHD) model for young pulsar wind nebulae (PWN) has been successful in reproducing many features of the nebulae. The model is characterized by a termination shock (TS) between the PWN and unshocked pulsar wind. Relativistic particles are injected at the TS and follow an advective flow to the outer boundary. However, toroidal structure of well studied young PWN like the Crab Nebula, 3C 58 and G21.5-0.9 is only present in the region close to the TS. In the outer parts of the nebulae, filamentary and loop-like structure is observed. Also, the radial variation of spectral index due to synchrotron losses is smoother than expected in the MHD flow model. We find that a pure diffusion model with energy independent diffusion and a transmitting boundary can reproduce the basic data on nebular size and spectral index variation for the Crab, 3C 58, and G21.5-0.9. Energy dependent diffusion is also discussed. Power law variations of the coefficient with energy are degenerate with variation in the input particle energy distribution index in the steady state case. Monte Carlo simulations of particle transport with both diffusion and advection for the Crab nebula and 3C 58 suggest a picture in which advection dominates the inner part of the PWN where toroidal structure is clearly present. Diffusion dominates the outer part of the PWN where filamentary and loop-like structure is observed. The source of the chaotic field is uncertain, but may be related to Rayleigh-Taylor instability at the outer boundary of young nebulae and/or the kink instability of the toroidal magnetic field.

scholarly journals The Radio Spectral Index of the Crab Nebula

1997 ◽  
Vol 490 (1) ◽  
pp. 291-301 ◽  
Author(s):  
M. F. Bietenholz ◽  
N. Kassim ◽  
D. A. Frail ◽  
R. A. Perley ◽  
W. C. Erickson ◽  
...  
Keyword(s):  
Spectral Index ◽  
Crab Nebula ◽  
The Crab Nebula

scholarly journals Upper Limit of the X-Ray Polarization of the Crab Nebula

1971 ◽  
Vol 46 ◽  
pp. 54-64
Author(s):  
R. Novick ◽  
J. R. P. Angel ◽  
R. S. Wolff
Keyword(s):  
Crab Nebula ◽  
Continuum Emission ◽  
X Ray ◽  
Upper Limit ◽  
Optical Continuum ◽  
The Crab Nebula

A rocket-borne X-ray polarimeter was flown to search for polarization in Taurus X-1. Although a result consistent with zero polarization was obtained, the statistics were such that X-ray polarization comparable in magnitude and direction to that of radio and optical continuum emission cannot be excluded.

scholarly journals The dust content of the Crab Nebula

2019 ◽  
Vol 488 (1) ◽  
pp. 164-182 ◽  
Author(s):  
I De Looze ◽  
M J Barlow ◽  
R Bandiera ◽  
A Bevan ◽  
M F Bietenholz ◽  
...  
Keyword(s):  
Spectral Index ◽  
Near Infrared ◽  
Crab Nebula ◽  
Dust Emission ◽  
Infrared Emission ◽  
Small Contribution ◽  
Dust Extinction ◽  
Dust Mass ◽  
The Crab Nebula ◽  
Dust Condensation

ABSTRACT We have modelled the near-infrared to radio images of the Crab Nebula with a Bayesian SED model to simultaneously fit its synchrotron, interstellar (IS), and supernova dust emission. We infer an IS dust extinction map with an average AV = 1.08 ± 0.38 mag, consistent with a small contribution (${\lesssim }22{{\ \rm per\ cent}}$) to the Crab’s overall infrared emission. The Crab’s supernova dust mass is estimated to be between 0.032 and 0.049 M⊙ (for amorphous carbon grains) with an average dust temperature Tdust = 41 ± 3 K, corresponding to a dust condensation efficiency of 8–12 ${{\ \rm per\ cent}}$. This revised dust mass is up to an order of magnitude lower than some previous estimates, which can be attributed to our different IS dust corrections, lower SPIRE flux densities, and higher dust temperatures than were used in previous studies. The dust within the Crab is predominantly found in dense filaments south of the pulsar, with an average V-band dust extinction of AV = 0.20–0.39 mag, consistent with recent optical dust extinction studies. The modelled synchrotron power-law spectrum is consistent with a radio spectral index αradio = 0.297 ± 0.009 and an infrared spectral index αIR = 0.429 ± 0.021. We have identified a millimetre excess emission in the Crab’s central regions, and argue that it most likely results from two distinct populations of synchrotron emitting particles. We conclude that the Crab’s efficient dust condensation (8–12 ${{\ \rm per\ cent}}$) provides further evidence for a scenario where supernovae can provide substantial contributions to the IS dust budgets in galaxies.

The Crab Nebula - High energy X-ray observation of a lunar occultation

1975 ◽  
Vol 201 ◽  
pp. L15 ◽  
Author(s):  
R. Staubert ◽  
E. Kendziorra ◽  
J. Truemper ◽  
C. Reppin ◽  
J. A. Hoffman ◽  
...  
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
X Ray ◽  
Lunar Occultation ◽  
The Crab Nebula

High-energy X-ray observations of a lunar occultation of the Crab Nebula

1975 ◽  
Vol 197 ◽  
pp. L83 ◽  
Author(s):  
G. R. Ricker ◽  
S. G. Ryckman ◽  
J. E. Ballintine ◽  
J. P. Doty ◽  
P. M. Downey ◽  
...  
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
X Ray ◽  
Lunar Occultation ◽  
The Crab Nebula

A Lunar Occultation of the Crab Nebula at 1420 Mc/sec.

1966 ◽  
Vol 71 ◽  
pp. 167 ◽  
Author(s):  
T. Krishnan ◽  
S. H. Zisk ◽  
D. D. Cudaback
Keyword(s):  
Crab Nebula ◽  
Lunar Occultation ◽  
The Crab Nebula

Lunar Occultation of X-ray Emission from the Crab Nebula

Science ◽  
1964 ◽  
Vol 146 (3646) ◽  
pp. 912-917 ◽  
Author(s):  
S. Bowyer ◽  
E. T. Byram ◽  
T. A. Chubb ◽  
H. Friedman
Keyword(s):  
Crab Nebula ◽  
X Ray ◽  
Lunar Occultation ◽  
The Crab Nebula
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