On the origin of sub-TeV gamma-ray pulsed emission from rotating neutron stars

Abstract

Intriguing sub-TeV tails in the pulsed $\gamma$-ray emission from the Crab pulsar have been recently discovered by the MAGIC and VERITAS Collaborations. They were not clearly predicted by any pulsar model. It is at present argued that this emission is produced by electrons in the Inverse Compton process occurring either in the outer gap of the pulsar magnetosphere or in the pulsar wind region at some distance from the light cylinder. We analyse another scenario which is consistent with the basic features of this enigmatic emission. It is proposed that this emission is caused by electrons accelerated very close to the light cylinder where the $e^{\pm }$ plasma can not saturate induced huge electric fields. Electrons reach energies sufficient for production of hard $\gamma$-ray spectra in the curvature radiation process. Due to different curvature radii of the leading and trailing magnetic field lines, the $\gamma$-ray spectra from separate pulses should extend to different maximum energies. The scenario can also explain the lower level $\gamma$-ray emission from the interpulse region (between P1 and P2) observed in the Crab pulsar light curve. Moreover, we argue that pulsars with parameters close to the Vela pulsar should also show pulsed emission with the cut-off at clearly lower energies ($\sim$50 GeV) than that observed in the case of the Crab pulsar. On the other hand, such tail emission is not expected in pulsars with parameters close to the Geminga pulsar. The model also predicts the tail $\gamma$-ray emission extending up to $\sim$50 GeV from some millisecond pulsars with extreme parameters such as PSR J0218+4243 and PSR J1823-3021A.

16 pages, 2 figures, accepted to MNRAS

References in corpus (4)

• VHE Gamma-Ray Observation of the Crab Nebula and its Pulsar with the MAGIC telescope
• Observation of Pulsed Gamma-rays Above 25 GeV from the Crab Pulsar with MAGIC
• Time-dependent pair cascades in magnetospheres of neutron stars I. Dynamics of the polar cap cascade with no particle supply from the neutron star surface
• Radio-to-TeV Phase-resolved Emission from the Crab Pulsar: The Annular Gap Model

Cited by in corpus (15)

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• Theory of pulsar magnetosphere and wind
• First Ground-based Measurement of Sub-20 GeV to 100 GeV $\gamma$-rays from the Vela Pulsar with H.E.S.S. II
• Detection of bridge emission above 50 GeV from the Crab pulsar with the MAGIC telescopes
• Search for VHE gamma-ray emission from Geminga pulsar and nebula with the MAGIC telescopes
• A Search for Pulsations from Geminga Above 100 GeV with VERITAS
• Magnetocentrifugal acceleration of bulk motion of plasma in pulsar magnetosphere
• Pulsed VHE emission from the Crab Pulsar in the context of magnetocentrifugal particle acceleration
• Prospects for the detection of high-energy (E>25 GeV) Fermi pulsars with the Cherenkov Telescope Array
• Does a strong particle accelerator arise very close to the light cylinder in a pulsar magnetosphere?
• Observation of the Black Widow B1957+20 millisecond pulsar binary system with the MAGIC telescopes
• Two-fluid model of the pulsar magnetosphere represented as an axisymmetric force-free dipole
• On the highest energy emission from millisecond pulsars
• Rotationally-driven VHE emission from the Vela pulsar