High Time Resolution Infrared Observations of the Crab Nebula Pulsar and the Pulsar Emission Mechanism

We investigate a stationary pair-production cascade in the outer magnetosphere of a spinning neutron star. The charge depletion due to global Ñows of charged particles causes a large electric Ðeld along the magnetic Ðeld lines. Migratory electrons and/or positrons are accelerated by this Ðeld to radiate curvature gamma rays, some of which collide with the X-rays to materialize as pairs in the gap. The replenished charges partially screen the electric Ðeld, which is self-consistently solved together with the distribution functions of particles and gamma rays. If no current is injected at either of the boundaries of the accelerator, the gap is located around the conventional null surface, where the local Goldreich-Julian charge density vanishes. However, we Ðrst Ðnd that the gap position shifts outward (or inward) when particles are injected at the inner (or outer) boundary. Applying the theory to the Crab pulsar, we demonstrate that the pulsed TeV Ñux does not exceed the observational upper limit for moderate infrared photon density and that the gap should be located near to or outside of the conventional null surface so that the observed spectrum of pulsed GeV Ñuxes may be emitted via a curvature process. Some implications of the existence of a solution for a super Goldreich-Julian current are discussed.

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“…Setting mJy at which is consistent with F l \ 3 v IR \ 10~6, near-IR and optical observations (Eikenberry et al 1997), we obtain cm~3. 5.2.…”

Section: Input Infrared Fieldsupporting

confidence: 74%

Electrodynamic Structure of an Outer Gap Accelerator: Location of the Gap and the Gamma‐Ray Emission from the Crab Pulsar

Hirotani

Shibata

2001

ApJ

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“…A similar result is obtained when only the main peak part of the pulse profile is used for this analysis. It is important to realize that this is only a statement about the phase-averaged arrival times of photons: the full width at halfmaximum (FWHM) of the pulse peak is known to decrease with decreasing wavelength (Percival et al 1993;Eikenberry et al 1997;Sollerman et al 2000). This trend is also evident in our data.…”

Section: Wavelength Dependence Of the Delayssupporting

confidence: 53%

Simultaneous absolute timing of the Crab pulsar at radio and optical wavelengths

Oosterbroek¹,

Cognard

Golden

et al. 2008

A&A

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Context. The Crab pulsar emits across a large part of the electromagnetic spectrum. Determining the time delay between the emission at different wavelengths will allow to better constrain the site and mechanism of the emission. We have simultaneously observed the Crab Pulsar in the optical with S-Cam, an instrument based on Superconducting Tunneling Junctions (STJs) with μs time resolution and at 2 GHz using the Nançay radio telescope with an instrument doing coherent dedispersion and able to record giant pulses data. Aims. We have studied the delay between the radio and optical pulse using simultaneously obtained data therefore reducing possible uncertainties present in previous observations. Methods. We determined the arrival times of the (mean) optical and radio pulse and compared them using the tempo2 software package.Results. We present the most accurate value for the optical-radio lag of 255±21 μs and suggest the likelihood of a spectral dependence to the excess optical emission asociated with giant radio pulses.

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“…For the Crab pulsar, the (isotropic, phase-averaged) near infrared-optical luminosity is of order L o ∼ 10 33 erg/s, turning significantly downward for lower frequencies (e.g., Middleditch et al 1983;Eikenberry et al 1997;Sollerman 2003). This suggests a photon energy density close to the light surface of order u ph ∼ L o /(4πr L c) ∼ 10 5 sin 2 α erg/cm 3 , comparable to the thermal one.…”

Section: Inverse Compton With Infrared Photonsmentioning

confidence: 91%

“…For a characteristic (observed pulsed Crab) photon field of L(0.1eV) L(1eV) < ∼ (1−3) × 10 33 erg/s (e.g., Eikenberry et al 1997;Sollerman 2003) this would result in…”

Section: Pair Creation and γγ-Absorptionmentioning

confidence: 99%

On particle acceleration and very high energy γ-ray emission in Crab-like pulsars

Osmanov

Rieger

2009

A&A

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Context. The origin of very energetic charged particles and the production of very high-energy (VHE) gamma-ray emission remains still a challenging issue in modern pulsar physics. Aims. By applying a toy model, we explore the acceleration of co-rotating charged particles close to the light surface in a plasma-rich pulsar magnetosphere and study their interactions with magnetic and photon fields under conditions appropriate for Crab-type pulsars. Methods. Centrifugal acceleration of particles in a monopol-like magnetic field geometry is analyzed and the efficiency constraints, imposed by corotation, inverse Compton interactions and curvature radiation reaction are determined. We derive expressions for the maximum particle energy and provide estimates for the corresponding high-energy curvature and inverse Compton power outputs. Results. It is shown that for Crab-like pulsars, electron Lorentz factor up to γ ∼ 10 7 can be achieved, allowing inverse Compton (Klein-Nishina) up-scattering of thermal photons to TeV energies with a maximum luminosity output of ∼10 31 erg/s. Curvature radiation, on the other hand, will result in a strong GeV emission output of up to ∼(10 34 −10 35 ) erg/s, quasi-exponentially decreasing towards higher energies for photon energies below ∼50 GeV. Conclusions. Accordingly to the results presented only young pulsars are expected to be sites of detectable VHE γ-ray emission.

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High Time Resolution Infrared Observations of the Crab Nebula Pulsar and the Pulsar Emission Mechanism

Cited by 32 publications

References 11 publications

Electrodynamic Structure of an Outer Gap Accelerator: Location of the Gap and the Gamma‐Ray Emission from the Crab Pulsar

Electrodynamic Structure of an Outer Gap Accelerator: Location of the Gap and the Gamma‐Ray Emission from the Crab Pulsar

Simultaneous absolute timing of the Crab pulsar at radio and optical wavelengths

On particle acceleration and very high energy γ-ray emission in Crab-like pulsars

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