Pulsed VHE emission from the Crab Pulsar in the context of magnetocentrifugal particle acceleration

Abstract

The Crab Pulsar has been recently detected at very high energies (VHE) with its pulsed VHE emission reaching up to 1.5 TeV. The VHE peaks appear synchronised with the peaks at GeV energies and show VHE spectra following hard power-law functions. These new findings have been interpreted as evidence for a gamma-ray production that happens very close to the light cylinder. Motivated by these experimental results we consider the efficiency of magnetocentrifugal particle acceleration in the magnetosphere of the Crab Pulsar, reexamining and extending results obtained in a previous work (Osmanov & Rieger 2009). It is shown that efficient magnetocentrifugal acceleration close to the light cylinder could provide the required electron Lorentz factors of 5 × 10 6 and that the resulting inverse Compton (IC) scattering off thermal photons might explain the enigmatic TeV emission of the pulsar. We estimate the corresponding VHE luminosity and provide a derivation of its spectral characteristics, that appear remarkably close to the observational results to encourage further studies.

Rotationally driven VHE emission from the Vela pulsar

“…In particular, applying magneto-centrifugal acceleration to Crab-like pulsars it was found that on approaching the LC area electrons could achieve Lorentz factor up to γ ∼ 10 7 (Osmanov & Rieger 2009;Bogovalov 2014), suggesting that inverse Compton (IC) scattering in the Crab Pulsar's magnetosphere could generate detectable pulsed VHE emission in the TeV band. A subsequent evaluation of the spectral characteristics (Osmanov & Rieger 2017) turned out to be in a good agreement with the observational data.…”

“…(4) suggests that rotationallydriven IC emission could well yield VHE emission up to several TeV. When compared to the Crab pulsar, where r otationallydriven curvature emission can lead to a detectable GeV contribution (Osmanov & Rieger 2017), supporting a smoother GeV-VHE connection, as indeed observed (Ansoldi et al 2016), rotationally-driven curvature emission in the Vela pulsar peaks at MeV energies only (eq. [5]); rotationally-driven IC VHE component in the Vela pulsar thus appears as a separate, second and new component.…”

“…(3)) has been used. The (effective) differential number of electrons, N e (γ) = dN e dγ , then becomes (Osmanov & Rieger 2017) N e (γ) = n e (γ)∆V ∝ n e (γ)d ∝ γ −5/2 ,…”

Observation of the black widow B1957+20 millisecond pulsar binary system with the MAGIC telescopes

“…For example, Lyutikov et al (2012) and Aleksić et al (2012) argue that this pulsed emission component is produced in the comptonization process occurring within the outer gap scenario. It is also suggested that electrons, accelerated close to the light cylinder radius (at a distance of 7 × 10 6 cm from the Black Widow pulsar), can produce γ rays in curvature process in the distorted magnetic field (Bednarek 2012;Bogovalov 2014) or due to IC scattering of thermal radiation from the NS surface (Osmanov & Rieger 2017). This emission could also come from the outside of the light cylinder radius, from the region of the equatorial current sheet (e.g.…”

Relativistic Effects of Rotation in γ-ray Pulsars—Invited Review

“…We apply the model of centrifugal acceleration to the wellknown Crab and Vela pulsars and normal period pulsars, and in Section 3, we outline the obtained results. [22]. The centrifugally accelerated co-rotating particles in the nearby zone of the LC area emit in a relatively narrow cone along the tangential direction.…”