Structure of relativistic shocks in pulsar winds: A model of the wisps in the Crab Nebula

1994 ◽  
Vol 435 ◽  
pp. 230 ◽  
Author(s):  
Yves A. Gallant ◽  
Jonathan Arons
Keyword(s):  
Crab Nebula ◽  
Relativistic Shocks ◽  
The Crab Nebula ◽  
Pulsar Winds

scholarly journals Reconnection in Pulsar Winds

2001 ◽  
Vol 18 (4) ◽  
pp. 415-420 ◽  
Author(s):  
J. G. Kirk ◽  
Y. Lyubarsky
Keyword(s):  
Magnetic Field ◽  
Energy Transport ◽  
Crab Nebula ◽  
Low Frequency ◽  
Frequency Wave ◽  
Poynting Flux ◽  
High Particle ◽  
The Crab Nebula ◽  
Pulsar Winds ◽  
The Magnetic Field

AbstractThe spin-down power of a pulsar is thought to be carried away in an MHD wind in which, at least close to the star, the energy transport is dominated by Poynting flux. The pulsar drives a low frequency wave in this wind, consisting of stripes of toroidal magnetic field of alternating polarity, propagating in a region around the equatorial plane. The current implied by this configuration falls off more slowly with radius than the number of charged particles available to carry it, so that the MHD picture must, at some point, fail. Recently, magnetic reconnection in such a structure has been shown to accelerate the wind significantly. This reduces the magnetic field in the comoving frame and, consequently, the required current, enabling the solution to extend to much larger radius. This scenario is discussed and, for the Crab Nebula, the range of validity of the MHD solution is compared with the radius at which the flow appears to terminate. For sufficiently high particle densities, it is shown that a low frequency entropy wave can propagate out to the termination point. In this case, the ‘termination shock’ itself must be responsible for dissipating the wave.This paper is dedicated to Don Melrose on his 60th birthday.

scholarly journals PeV Emission of the Crab Nebula: Constraints on the Proton Content in Pulsar Wind and Implications

2021 ◽  
Vol 922 (2) ◽  
pp. 221
Author(s):  
Ruo-Yu Liu ◽  
Xiang-Yu Wang
Keyword(s):  
Energy Content ◽  
Crab Nebula ◽  
Cosmic Ray ◽  
Ultrahigh Energy ◽  
Pulsar Wind Nebulae ◽  
Air Shower ◽  
Pulsar Wind ◽  
The Crab Nebula ◽  
Pulsar Winds ◽  
Cosmic Ray Flux

Abstract Recently, two photons from the Crab Nebula with energy of approximately 1 PeV were detected by the Large High Altitude Air Shower Observatory (LHAASO), opening an ultrahigh-energy window for studying pulsar wind nebulae (PWNe). Remarkably, the LHAASO spectrum at the highest-energy end shows a possible hardening, which could indicate the presence of a new component. A two-component scenario with a main electron component and a secondary proton component has been proposed to explain the whole spectrum of the Crab Nebula, requiring a proton energy of 1046–1047 erg remaining in the present Crab Nebula. In this paper, we study the energy content of relativistic protons in pulsar winds using the LHAASO data of the Crab Nebula, considering the effect of diffusive escape of relativistic protons. Depending on the extent of the escape of relativistic protons, the total energy of protons lost in the pulsar wind could be 10–100 times larger than that remaining in the nebula presently. We find that the current LHAASO data allow up to (10–50)% of the spindown energy of pulsars being converted into relativistic protons. The escaping protons from PWNe could make a considerable contribution to the cosmic-ray flux of 10–100 PeV. We also discuss the leptonic scenario for the possible spectral hardening at PeV energies.

scholarly journals Particle Acceleration in Gamma-Ray Bursts

2005 ◽  
Vol 192 ◽  
pp. 475-482
Author(s):  
J.G. Kirk
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Shock Front ◽  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Magnetic Field Generation ◽  
Relativistic Shocks ◽  
The Crab Nebula

SummarySimple kinematic theories of particle acceleration at relativistic shocks lead to the prediction of a high-energy spectral index of −1.1 for the energy flux of synchrotron photons. However, several effects can change this picture. In this paper I discuss the effect of magnetic field generation at the shock front and, by analogy with the Crab Nebula, suggest that an intrinsic break in the injection spectrum should be expected where the electron gyro radius is comparable to that of protons thermalized by the shock.

scholarly journals Pulsar Winds

1996 ◽  
Vol 160 ◽  
pp. 401-408
Author(s):  
Jonathan Arons
Keyword(s):  
Shock Waves ◽  
Gamma Rays ◽  
Crab Nebula ◽  
Theoretical Work ◽  
High Energy ◽  
Time Variable ◽  
Recent Theoretical Work ◽  
Energy Gamma ◽  
The Crab Nebula ◽  
Pulsar Winds

AbstractThe shock excitation of pulsar powered nebulae (plerions) is discussed, based on recent theoretical work on the structure of relativistic, collisionless magnetosonic shock waves. This theory is used to outline a model in which theγ−2injection spectrum of the Crab Nebula is satisfactorily accounted for. The same theory suggests a model of the “wisp” features in the Crab Nebula which accounts for these time variable features in the surface bightness as compressions associated with the magnetic overshootswithinthe shock structure. It is pointed out that this theory suggests observable variability in the high energy gamma rays from the Crab Nebula (ε > 50 MeV).

scholarly journals Shocks and Wind Bubbles Around Energetic Pulsars

2004 ◽  
Vol 218 ◽  
pp. 151-158 ◽  
Author(s):  
Bryan M. Gaensler
Keyword(s):  
Ambient Medium ◽  
Crab Nebula ◽  
Quality Data ◽  
Time Variability ◽  
Electromagnetic Spectrum ◽  
Pulsar Wind Nebulae ◽  
High Quality Data ◽  
Bow Shocks ◽  
The Crab Nebula ◽  
Pulsar Winds

The Crab Nebula demonstrates that neutron stars can interact with their environments in spectacular fashion, their relativistic winds generating nebulae observable across the electromagnetic spectrum. At many previous conferences, astronomers have discussed, debated and puzzled over the complicated structures seen in the Crab, but have been limited to treating most other pulsar wind nebulae (PWNe) as simple calorimeters for a pulsar's spin-down energy. However, with the wealth of high-quality data which have now become available, this situation has changed dramatically. I here review some of the main observational themes which have emerged from these new measurements. Highlights include the ubiquity of pulsar termination shocks, the unambiguous presence of relativistic jets in PWNe, complicated time variability seen in PWN structures, and the use of bow shocks to probe the interaction of pulsar winds with the ambient medium.

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.

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