Magnetic absorption of VHE photons in the magnetosphere of the Crab pulsar

Abstract

The detection of the pulsed $\sim 1$~TeV gamma-ray emission from the Crab pulsar reported by MAGIC and VERITAS collaborations demands a substantial revision of existing models of particle acceleration in the pulsar magnetosphere. In this regard model independent restrictions on the possible production site of the VHE photons become an important issue. In this paper, we consider limitations imposed by the process of conversion of VHE gamma rays into $e^{\pm }$ pairs in the magnetic field of the pulsar magnetosphere. Photons with energies exceeding 1~TeV are effectively absorbed even at large distances from the surface of the neutron star. Our calculations of magnetic absorption in the force-free magnetosphere show that the twisting of the magnetic field due to the pulsar rotation makes the magnetosphere more transparent compared to the dipole magnetosphere. The gamma-ray absorption appears stronger for photons emitted in the direction of rotation than in the opposite direction. There is a small angular cone inside which the magnetosphere is relatively transparent and photons with energy $1.5$~TeV can escape from distances beyond $0.1$~light cylinder radius ($R_{\mathrm{lc}}$). The emission surface from where photons can be emitted in the observer's direction further restricts the sites of VHE gamma-ray production. For the observation angle $57^{\circ }$ relative to the Crab pulsar axis of rotation and the orthogonal rotation, the emission surface in the open field line region is located as close as $0.4R_{\mathrm{lc}}$ from the stellar surface for a dipole magnetic field, and $0.1R_{\mathrm{lc}}$ for a force-free magnetic field.

arXiv comment22 pages, 9 figures

References in corpus (37)

• Shapiro delay measurement of a two solar mass neutron star
• A Massive Pulsar in a Compact Relativistic Binary
• Time-dependent force-free pulsar magnetospheres: axisymmetric and oblique rotators
• The Axisymmetric Pulsar Magnetosphere
• Detection of 16 Gamma-Ray Pulsars Through Blind Frequency Searches Using the Fermi LAT
• Gamma Ray Pulsars: Emission from Extended Polar Cap Cascades
• Modeling of Gamma-Ray Pulsar Light Curves with Force-Free Magnetic Field
• On the force-free magnetosphere of aligned rotator
• High-Altitude Particle Acceleration and Radiation in Pulsar Slot Gaps
• Simulations of Axisymmetric Magnetospheres of Neutron Stars
• Detection of Pulsed Gamma Rays Above 100 GeV from the Crab Pulsar
• The Power of Axisymmetric Pulsar
• Three-dimensional numerical simulations of the pulsar magentoshere: Preliminary results
• Pair-production multiplicities in rotation-powered pulsars
• Time-Dependent 3D Magnetohydrodynamic Pulsar Magnetospheres: Oblique Rotators
• Teraelectronvolt pulsed emission from the Crab pulsar detected by MAGIC
• Evolution of the Magnetic Field Structure of the Crab Pulsar
• The Vela Pulsar: Results from the First Year of Fermi LAT Observations
• Atmospheres and radiating surfaces of neutron stars
• Relativistic Force-Free Electrodynamic Simulations of Neutron Star Magnetospheres
• Phase-resolved energy spectra of the Crab Pulsar in the range of 50-400 GeV measured with the MAGIC Telescopes
• An Outer Gap Model of High-Energy Emission from Rotation-Powered Pulsars
• Introducing PHAEDRA: a new spectral code for simulations of relativistic magnetospheres
• Very-high-energy gamma radiation associated with the unshocked wind of the Crab pulsar
• Magnetic dissipation in the Crab Nebula
• Three-dimensional Analytical Description of Magnetised Winds from Oblique Pulsars
• Uncertainties of Modeling Gamma-Ray Pulsar Light Curves with Vacuum Dipole Magnetic Field
• The Extended Pulsar Magnetosphere
• The pulsar synchrotron in 3D: curvature radiation
• Acceleration and collimation of relativistic plasmas ejected by fast rotators
• General-relativistic force-free pulsar magnetospheres
• Synchro-curvature radiation of charged particles in the strong curved magnetic fields
• A High-Order WENO-based Staggered Godunov-type Scheme with Constrained Transport for Force-free Electrodynamics
• On particle acceleration and very high energy gamma-ray emission in Crab-like pulsars
• The spectral simulations of axisymmetric force-free pulsar magnetosphere
• Magnetocentrifugal acceleration of bulk motion of plasma in pulsar magnetosphere
• Magnetic Pair Creation Transparency in Gamma-Ray Pulsars

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