Fermi Gamma-ray Space Telescope

Multi-TeV Emission From the Vela Pulsar

(C. Kalapotharakos, M. Barnard, C. Venter)


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 near the current sheet. The synchrotron spectrum from pairs resonantly absorbing radio photons at relatively low altitude can account for the observed IR-optical emission. The particles in the current sheet, accelerated to energies of 30-60 TeV, produce GeV emission through curvature radiation and 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 multi-TeV observed emission.