scholarly journals On the Radio Emitting Particles of the Crab Nebula: Stochastic Acceleration Model

2017 ◽  
Vol 13 (S337) ◽  
pp. 259-262
Author(s):  
Shuta J. Tanaka
Keyword(s):  
Crab Nebula ◽  
Supernova Explosion ◽  
Shock Acceleration ◽  
Back Reaction ◽  
Acceleration Process ◽  
Spectral Evolution ◽  
Stochastic Acceleration ◽  
Acceleration Model ◽  
Pulsar Wind ◽  
The Crab Nebula

AbstractThe standard shock acceleration model of pulsar wind nebulae (PWNe) does not account for the hard spectrum in radio wavelengths. The origin of the radio-emitting particles is also important to determine the pair production efficiency in the pulsar magnetosphere. Here, we propose a possible resolution for the particle energy distribution in PWNe; the radio-emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by turbulence inside PWNe. We upgrade our past one-zone spectral evolution model including the energy diffusion, i.e., the stochastic acceleration, and apply to the Crab Nebula. For a particle injection to the stochastic acceleration process, we consider the continuous injection from the supernova ejecta or the impulsive injection associated with supernova explosion. The observed broadband spectrum and the decay of the radio flux are reproduced by tuning the amount of the particle injected to the stochastic acceleration process. Our results imply that some unveiled mechanisms, such as back reaction to the turbulence, are required to make the energies of stochastically and shock accelerated particles comparable.

scholarly journals A corrugated termination shock in pulsar wind nebulae?

2016 ◽  
Vol 82 (4) ◽  
Author(s):  
Martin Lemoine
Keyword(s):  
Magnetic Field ◽  
Crab Nebula ◽  
Radiation Reaction ◽  
Termination Shock ◽  
Pulsar Wind Nebulae ◽  
Order Unity ◽  
Poynting Flux ◽  
Electron Positron ◽  
Pulsar Wind ◽  
The Crab Nebula

Successful phenomenological models of pulsar wind nebulae assume efficient dissipation of the Poynting flux of the magnetized electron–positron wind as well as efficient acceleration of the pairs in the vicinity of the termination shock, but how this is realized is not yet well understood. This paper suggests that the corrugation of the termination shock, at the onset of nonlinearity, may lead towards the desired phenomenology. Nonlinear corrugation of the termination shock would convert a fraction of order unity of the incoming ordered magnetic field into downstream turbulence, slowing down the flow to sub-relativistic velocities. The dissipation of turbulence would further preheat the pair population on short length scales, close to equipartition with the magnetic field, thereby reducing the initial high magnetization to values of order unity. Furthermore, it is speculated that the turbulence generated by the corrugation pattern may sustain a relativistic Fermi process, accelerating particles close to the radiation reaction limit, as observed in the Crab nebula. The required corrugation could be induced by the fast magnetosonic modes of downstream nebular turbulence; but it could also be produced by upstream turbulence, either carried by the wind or seeded in the precursor by the accelerated particles themselves.

scholarly journals Year-scale Morphological Variation of the X-ray Crab Nebula

2004 ◽  
Vol 218 ◽  
pp. 181-184 ◽  
Author(s):  
Koji Mori ◽  
David N. Burrows ◽  
George G. Pavlov ◽  
J. Jeff Hester ◽  
Shinpei Shibata ◽  
...  
Keyword(s):  
Morphological Variation ◽  
Crab Nebula ◽  
The Other ◽  
X Ray ◽  
Morphological Variations ◽  
Other Hand ◽  
Pulsar Wind ◽  
Circular Structures ◽  
The Crab Nebula

We present year-scale morphological variations of the Crab Nebula revealed by the Chandra X-ray Observatory. Observations have been performed about every 1.7 years over the three years from launch. The variations are clearly recognized at two sites: the torus and the southern jet. The torus, which had been steadily expanding until 1.7 years ago, now appears to have shrunk in the latest observation. Additionally, the circular structures seen to the northeast of the torus have decayed into several arcs. On the other hand, the southern jet shows the growth of its overall kinked-structure. We discuss the nature of these variations in terms of the pulsar wind nebula mechanism.

scholarly journals High Resolution X-ray Observations of 3C 58

2004 ◽  
Vol 218 ◽  
pp. 185-188
Author(s):  
Patrick Slane
Keyword(s):  
High Resolution ◽  
Massive Star ◽  
Thermal Emission ◽  
Rotation Axis ◽  
Crab Nebula ◽  
X Ray ◽  
The Galaxy ◽  
Pulsar Wind ◽  
Star Surface ◽  
The Crab Nebula

As the presumed remnant of SN 1181, 3C 58 houses one of the youngest known neutron stars in the Galaxy. The properties of this young pulsar and its associated pulsar wind nebula (PWN) differ considerably from those of the Crab Nebula, and may well offer a more typical example of the endpoint of massive star collapse. High resolution X-ray studies reveal structures in the inner nebula that may be associated with the pulsar wind termination shock, a jet that may be aligned with the rotation axis, and other regions of enhanced emission. Spectral variations in the PWN are consistent with the expected evolution of the postshock flow, and complex loops of emission are seen in the nebula interior. Limits on the neutron star surface temperature fall below standard cooling models, indicating that some more rapid neutrino cooling process is required. The outer regions of 3C 58 show thermal emission with enhanced levels of neon, indicative of shocked ejecta bounding the PWN.

Crab Supernova Rock Art

2015 ◽  
Vol 1 (2) ◽  
pp. 167-197 ◽  
Author(s):  
E. C. Krupp
Keyword(s):  
New Mexico ◽  
Critical Review ◽  
Crab Nebula ◽  
Rock Art ◽  
Supernova Explosion ◽  
American Southwest ◽  
The Sun ◽  
Detailed Evaluation ◽  
The Crab Nebula

“Star” and crescent combinations in rock art in the American Southwest were first interpreted in 1955 as eyewitness depictions of the 1054 AD supernova explosion that produced the Crab nebula. While the Crab nebula is visible only telescopically, the event that generated it was brilliant, and for a time, only the sun and moon were brighter. Additional Crab supernova candidates in California and Southwest rock art were suggested 20 years later, and they included Chaco Canyon’s Penasco Blanco pictograph panel, which became the poster child for Crab supernova rock art and is now called “Supernova” on signage at the site. By 1979, a list of 21 Crab supernova rock art sites was assembled, and the inventory has continued to expand more slowly since then. This critical review of the supernova interpretation of star/crescent rock art, the product of 35 years of fieldwork, required an independent re-examination of all of the primary sites in person. That enterprise has already demonstrated that the Tenabo, New Mexico panel does not illustrate the Crab supernova and that the two Arizona sites on which the entire supernova rock art premise is based (White Mesa and “Navaho Canyon”) are unlikely records of the event. This detailed evaluation of the primary proposed star/crescent images indicates none is a satisfactory portrayal of the striking 1054 AD supernova.

scholarly journals Time-variability of the Crab Nebula wisps

2000 ◽  
Vol 177 ◽  
pp. 507-508 ◽  
Author(s):  
Anatoly Spitkovsky ◽  
Jonathan Arons
Keyword(s):  
Magnetic Field ◽  
Crab Nebula ◽  
Propagation Speed ◽  
Time Dependent ◽  
Time Variability ◽  
Electron Positron ◽  
Pair Density ◽  
Pulsar Wind ◽  
The Crab Nebula ◽  
The Waves

AbstractWe present results of time-dependent numerical modeling of the internal structure of the collisionless shock terminating the pulsar wind in Crab Nebula. We treat the equatorial relativistic wind as composed of ions and electron-positron plasma with an embedded toroidal magnetic field. Relativistic cyclotron instability of the ion ring downstream from the shock is found to launch outward propagating magnetosonic waves. Due to the fresh supply of ions crossing the shock, the time-dependent process achieves a limit-cycle pattern, in which the waves are launched with periodicity on the order of the ion Larmor time. Compressions in magnetic field and pair density associated with these waves as well as their propagation speed qualitatively reproduce the features observed in the wisps.

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 Relationship Between Pulsar and Nebula

1971 ◽  
Vol 46 ◽  
pp. 389-391
Author(s):  
L. Woltjer
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Energy Supply ◽  
Crab Nebula ◽  
Supernova Explosion ◽  
Relativistic Electrons ◽  
The Crab Nebula ◽  
The Magnetic Field

The magnetic field and the relativistic electrons in the Crab Nebula cannot have originated at the time of the supernova explosion. The energy density in the magnetic field is so large that it must have been generated using the energy supply in the pulsar. The energies of the electrons are so high, and their lifetimes correspondingly are so short, that they must have been accelerated, again using the pulsar energy. The efficiency of these processes must be high, but there is an adequate energy supply.

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 Reverberation of pulsar wind nebulae (I): impact of the medium properties and other parameters upon the extent of the compression

2020 ◽  
Vol 499 (2) ◽  
pp. 2051-2062 ◽  
Author(s):  
R Bandiera ◽  
N Bucciantini ◽  
J Martín ◽  
B Olmi ◽  
D F Torres
Keyword(s):  
Ambient Medium ◽  
Crab Nebula ◽  
Late Phase ◽  
Pulsar Wind Nebulae ◽  
Reverse Shock ◽  
Pressure Profiles ◽  
Pulsar Wind ◽  
Radiation Processes ◽  
The Crab Nebula

ABSTRACT The standard approach to the long-term evolution of pulsar wind nebulae (PWNe) is based on one-zone models treating the nebula as a uniform system. In particular for the late phase of evolved systems, many of the generally used prescriptions are based on educated guesses for which a proper assessment lacks. Using an advanced radiative code, we evaluate the systematic impact of various parameters, like the properties of the supernova ejecta, of the inner pulsar, as well of the ambient medium, upon the extent of the reverberation phase of PWNe. We investigate how different prescriptions shift the starting time of the reverberation phase, how this affects the amount of the compression, and how much of this can be ascribable to the radiation processes. Some critical aspects are the description of the reverse shock evolution, the efficiency by which at later times material from the ejecta accretes on to the swept-up shell around the PWN, and finally the density, velocity, and pressure profiles in the surrounding supernova remnant. We have explicitly treated the cases of the Crab Nebula, and of J1834.9−0846, taken to be representatives of the more and the less energetic pulsars, respectively. Especially for the latter object, the prediction of large compression factors is confirmed, even larger in the presence of radiative losses, also confirming our former prediction of periods of superefficiency during the reverberation phase of some PWNe.

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