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Author Tanaka, Shuta J. ♦ Asano, Katsuaki
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ ACCELERATION ♦ COMPARATIVE EVALUATIONS ♦ CRAB NEBULA ♦ DECAY ♦ DIFFUSION ♦ EFFICIENCY ♦ ELECTRONS ♦ EMISSION ♦ ENERGY SPECTRA ♦ EVOLUTION ♦ EXPLOSIONS ♦ INJECTION ♦ PAIR PRODUCTION ♦ POSITRONS ♦ PULSARS ♦ RESOLUTION ♦ STELLAR WINDS ♦ STOCHASTIC PROCESSES ♦ TURBULENCE ♦ WAVELENGTHS
Abstract The broadband emission of pulsar wind nebulae (PWNe) is well described by non-thermal emissions from accelerated electrons and positrons. However, the standard shock acceleration model of PWNe does not account for the hard spectrum in radio wavelengths. The origin of the radio-emitting particles is also important to determine the pair production efficiency in the pulsar magnetosphere. Here, we propose a possible resolution for the particle energy distribution in PWNe; the radio-emitting particles are not accelerated at the pulsar wind termination shock but are stochastically accelerated by turbulence inside PWNe. We upgrade our past one-zone spectral evolution model to include the energy diffusion, i.e., the stochastic acceleration, and apply the model to the Crab Nebula. A fairly simple form of the energy diffusion coefficient is assumed for this demonstrative study. For a particle injection to the stochastic acceleration process, we consider the continuous injection from the supernova ejecta or the impulsive injection associated with supernova explosion. The observed broadband spectrum and the decay of the radio flux are reproduced by tuning the amount of the particle injected to the stochastic acceleration process. The acceleration timescale and the duration of the acceleration are required to be a few decades and a few hundred years, respectively. Our results imply that some unveiled mechanisms, such as back reaction to the turbulence, are required to make the energies of stochastically and shock-accelerated particles comparable.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2017-06-01
Publisher Place United States
Journal Astrophysical Journal
Volume Number 841
Issue Number 2


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