Very high energy emission as a probe of relativistic magnetic reconnection in pulsar winds

Abstract

The population of gamma-ray pulsars, including Crab observed in the TeV range, and Vela detected above 50 GeV, challenges existing models of pulsed high-energy emission. Such models should be universally applicable, yet they should account for spectral differences among the pulsars. We show that the gamma-ray emission of Crab and Vela can be explained by synchrotron radiation from the current sheet of a striped wind, expanding with a modest Lorentz factor $\Gamma \lesssim 100$ in the Crab case, and $\Gamma \lesssim 50$ in the Vela case. In the Crab spectrum a new synchrotron self-Compton component is expected to be detected by the upcoming experiment CTA. We suggest that the gamma-ray spectrum directly probes the physics of relativistic magnetic reconnection in the striped wind. In the most energetic pulsars, like Crab, with ${\dot{E}}_{38}^{3/2}/P_{-2}\gtrsim 0.002$ (where $\dot{E}$ is the spin down power, $P$ is the pulsar period, and $X=X_i\times 10^i$ in CGS units), reconnection proceeds in the radiative cooling regime and results in a soft power-law distribution of cooling particles; in less powerful pulsars, like Vela, particle energization is limited by the current sheet size, and a hard particle spectrum reflects the acceleration mechanism. A strict lower limit on the number density of radiating particles corresponds to emission close to the light cylinder, and, in units of the GJ density, it is $\gtrsim 0.5$ in the Crab wind, and $\gtrsim 0.05$ in the Vela wind.

published version; corrected typo, added reference

References in corpus (3)

• Formation of Hard Power-laws in the Energetic Particle Spectra Resulting from Relativistic Magnetic Reconnection
• A one-dimensional Vlasov-Maxwell equilibrium for the force-free Harris sheet
• Fermi-LAT Detection of Pulsed Gamma-rays Above 50 GeV from the Vela Pulsar

Cited by in corpus (12)

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• Pulsed VHE emission from the Crab Pulsar in the context of magnetocentrifugal particle acceleration
• The INTEGRAL view of the pulsating hard X-ray sky: from accreting and transitional millisecond pulsars to rotation-powered pulsars and magnetars
• Prospects for the detection of high-energy (E>25 GeV) Fermi pulsars with the Cherenkov Telescope Array
• A Search for Pulsed Very High-Energy Gamma Rays from Thirteen Young Pulsars in Archival VERITAS Data
• Electron acceleration at pulsar wind termination shocks
• Prospects for the characterization of the VHE emission from the Crab Nebula and Pulsar with the Cherenkov Telescope Array
• Dark photon constraints using the UHE gamma-ray emission from galactic sources. A Phenomenological Study
• Rotationally-driven VHE emission from the Vela pulsar