Two-zone model for the broadband Crab nebula spectrum: microscopic interpretation

¹ Depts. of Planetary Sciences and Astronomy, University of Arizona, Tucson, AZ, 85721, USA
² DESY, 15738 Zeuthen, Germany
³ Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany

^a e-mail: ffrasche@lpl.arizona.edu

Published online: 23 March 2017

Abstract

We develop a simple two-zone interpretation of the broadband baseline Crab nebula spectrum between 10⁻⁵ eV and ~ 100 TeV by using two distinct log-parabola energetic electrons distributions. We determine analytically the very-high energy photon spectrum as originated by inverse-Compton scattering of the far-infrared soft ambient photons within the nebula off a first population of electrons energized at the nebula termination shock. The broad and flat 200 GeV peak jointly observed by Fermi/LAT and MAGIC is naturally reproduced. The synchrotron radiation from a second energetic electron population explains the spectrum from the radio range up to ~ 10 keV. We infer from observations the energy dependence of the microscopic probability of remaining in proximity of the shock of the accelerating electrons.