Multi-TeV Emission From the Vela Pulsar

Abstract

Pulsed emission from the Vela pulsar at energies above 3 TeV has recently been detected by the H.E.S.S. II air-Cherenkov telescope. We present a model for the broad-band spectrum of Vela from infra-red (IR) to beyond 10 TeV. Recent simulations of the global pulsar magnetosphere have shown that most of the particle acceleration occurs in the equatorial current sheet outside the light cylinder and that the magnetic field structure is nearly force-free for younger pulsars. We adopt this picture to compute the radiation from both electron-positron pairs produced in polar cap cascades and from primary particles accelerated in the separatrix and current sheet. The synchrotron spectrum from pairs resonantly absorbing radio photons at relatively low altitude can account for the observed IR-optical emission. We set the parallel electric field in the current sheet to produce the Fermi GeV emission through curvature radiation, producing particles with energies of 30-60 TeV. These particles then produce Very-High-Energy emission up to around 30 TeV through inverse-Compton scattering of the IR-Optical emission. We present model spectra and light curves that can match the IR-Optical, GeV and make predictions for the multi-TeV emission.