scholarly journals On the Structure of the Crab Nebula

1979 ◽  
Vol 32 (2) ◽  
pp. 105 ◽  
Author(s):  
LI Matveyenko ◽  
VI Kostenko
Keyword(s):  
Crab Nebula ◽  
Detailed Structure ◽  
Physical Conditions ◽  
The Crab Nebula

Utilizing a large number of published observations, we investigate the detailed structure of the Crab Nebula over a range of wavelengths from 3�5 mm to 75 em, and identify many different features. The spectra of some of these features are followed to longer wavelengths, extending to nearly 10 m. Physical conditions within the features are discussed.

Faraday rotation and physical conditions in the Crab Nebula

1991 ◽  
Vol 368 ◽  
pp. 231 ◽  
Author(s):  
Michael F. Bietenholz ◽  
Philipp P. Kronberg
Keyword(s):  
Faraday Rotation ◽  
Crab Nebula ◽  
Physical Conditions ◽  
The Crab Nebula

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.

scholarly journals Optical Observations of the Crab Nebula

1971 ◽  
Vol 46 ◽  
pp. 3-11
Author(s):  
Virginia Trimble
Keyword(s):  
Crab Nebula ◽  
Emission Lines ◽  
Optical Observations ◽  
Continuum Radiation ◽  
Physical Conditions ◽  
The Crab Nebula ◽  
The Continuum

The continuum radiation from the Crab Nebula has a great deal of structure, the majority of which is strongly polarized. Wisps in the vicinity of the pulsar at the centre of the nebula move noticeably in a few months. The appearance of the nebula changes markedly when photographed in different emission lines, as a result of the variations of physical conditions from place to place within the nebula.

Observation of Polarization for the Crab Nebula with PHENEX Polarimeter

2010 ◽  
Vol 8 (ists27) ◽  
pp. Tm_35-Tm_40 ◽  
Author(s):  
Yuji KISHIMOTO ◽  
Shuichi GUNJI ◽  
Yushi ISHIKAWA ◽  
Makoto TAKADA ◽  
Tatehiro MIHARA ◽  
...  
Keyword(s):  
Crab Nebula ◽  
The Crab Nebula

A Model for the Moving “Wisps” in the Crab Nebula

1999 ◽  
Vol 512 (2) ◽  
pp. 755-760 ◽  
Author(s):  
Mitchell C. Begelman
Keyword(s):  
Crab Nebula ◽  
The Crab Nebula

scholarly journals Strong Waves from Pulsars and Morphologies in SNRs

1983 ◽  
Vol 101 ◽  
pp. 499-501
Author(s):  
Gregory Benford ◽  
Attilio Ferrari ◽  
Silvano Massaglia
Keyword(s):  
Large Amplitude ◽  
Crab Nebula ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Optical Emission ◽  
Amplitude Wave ◽  
Surface Magnetic Field ◽  
Plasma Absorption ◽  
The Crab Nebula ◽  
Large Amplitude Wave

Canonical models for pulsars predict the emission of low–frequency waves of large amplitudes, produced by the rotation of a neutron star possessing a strong surface magnetic field. Pacini (1968) proposed this as the basic drain which yields to the pulsar slowing–down rate. The main relevance of the large amplitude wave (LAW) is the energetic link it provides between the pulsar and the surrounding medium. This role has been differently emphasized (Rees and Gunn, 1974; Ferrari, 1974), referring to absorption effects by relativistic particle acceleration and thermal heating, either close to the pulsar magnetosphere or in the nebula. It has been analyzed in the special case of the Crab Nebula, where observations are especially rich (Rees, 1971). As the Crab Nebula displays a cavity around the pulsar of dimension ∼1017cm, the function of the wave in sweeping dense gas away from the circumpulsar region is widely accepted. Absorption probably occurs at the inner edges of the nebula; i.e., where the wave pressure and the nebular pressure come into balance. Ferrari (1974) interpreted the wisps of the Crab Nebula as the region where plasma absorption occurs, damping the large amplitude wave and driving “parametric” plasma turbulence, thus trasferring energy to optical radiation powering the nebula. The mechanism has been extended to interpret the specific features of the “wisps” emission (Benford et al., 1978). Possibly the wave fills the nebula completely, permeating the space outside filaments with electromagnetic energy, continuously accelerating electrons for the extended radio and optical emission (Rees, 1971).

scholarly journals The Crab nebula variability at short time-scales with the Cherenkov telescope array

2020 ◽  
Vol 501 (1) ◽  
pp. 337-346
Author(s):  
E Mestre ◽  
E de Oña Wilhelmi ◽  
D Khangulyan ◽  
R Zanin ◽  
F Acero ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Telescope Array ◽  
Cherenkov Telescopes ◽  
Cherenkov Telescope ◽  
Emission Models ◽  
Short Time ◽  
The Crab Nebula

ABSTRACT Since 2009, several rapid and bright flares have been observed at high energies (>100 MeV) from the direction of the Crab nebula. Several hypotheses have been put forward to explain this phenomenon, but the origin is still unclear. The detection of counterparts at higher energies with the next generation of Cherenkov telescopes will be determinant to constrain the underlying emission mechanisms. We aim at studying the capability of the Cherenkov Telescope Array (CTA) to explore the physics behind the flares, by performing simulations of the Crab nebula spectral energy distribution, both in flaring and steady state, for different parameters related to the physical conditions in the nebula. In particular, we explore the data recorded by Fermi during two particular flares that occurred in 2011 and 2013. The expected GeV and TeV gamma-ray emission is derived using different radiation models. The resulting emission is convoluted with the CTA response and tested for detection, obtaining an exclusion region for the space of parameters that rule the different flare emission models. Our simulations show different scenarios that may be favourable for achieving the detection of the flares in Crab with CTA, in different regimes of energy. In particular, we find that observations with low sub-100 GeV energy threshold telescopes could provide the most model-constraining results.

scholarly journals New Measurement of the Vertical Atmospheric Density Profile from Occultations of the Crab Nebula with X-Ray Astronomy Satellites Suzaku and Hitomi

2020 ◽  
Author(s):  
Satoru Katsuda ◽  
Hitoshi Fujiwara ◽  
Yoshitaka Ishisaki ◽  
Yoshitomo Maeda ◽  
Koji Mori ◽  
...  
Keyword(s):  
Density Profile ◽  
Crab Nebula ◽  
Atmospheric Density ◽  
X Ray ◽  
The Crab Nebula

Preferential acceleration of heavy ions from thermal velocities

1968 ◽  
Vol 46 (10) ◽  
pp. S638-S641 ◽  
Author(s):  
D. B. Melrose
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Heavy Ions ◽  
Crab Nebula ◽  
Low Frequency ◽  
High Frequency Waves ◽  
Hydromagnetic Waves ◽  
The Crab Nebula ◽  
Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

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