Rotationally driven VHE emission from the Vela pulsar

Abstract

Context. The recent detection of pulsed γ-ray emission from the Vela pulsar in the ∼ 10 to 100 GeV range by H.E.S.S. promises an important potential to probe into the very high energy (VHE) radiation mechanisms of pulsars. Aims. A combined analysis of H.E.S.S. and Fermi-LAT data suggests that the leading wing of the P2 peak shows a new, hard gammaray component (with photon index as hard as Γ ∼ 3.5), setting in above 50 GeV and extending beyond 100 GeV. We study these findings in the context of rotationally-driven (centrifugal) particle acceleration. Methods. We analyze achievable particle energies in the magnetosphere of the Vela pulsar, and calculate the resultant emission properties.Results. Inverse Compton up-scattering of thermal photons from the surface of the star is shown to lead a pulsed VHE contribution reaching into the TeV regime with spectral characteristics compatible with current findings. If confirmed by further observations this could be the second case where rotationally-driven processes turn out to be important to understand the VHE emission in young pulsars.

Synchrotron emission from the depths of pulsar magnetospheres

“…It is clear that generation of radiation requires efficient acceleration of particles. In general it is thought that particles might accelerate from a nearby region of the polar caps (polar cap acceleration) (Nobuyuki & Shinpei 2003;Harding & Muslimov 1998;Cheng & Ruderman 1980) as well as from the outer magnetosphere, by means of the so called outer gap mechanism (Hirotani 2015;Takata et al 2008) or centrifugal acceleration (Osmanov & Rieger 2019, 2017, 2009.…”