A compact pulsar wind nebula model of the gamma-ray loud binary LS I 61 303 - AstrophysicsReport as inadecuate

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Abstract: We study a model of of LS I +61 303 in which its radio to TeV emission is dueto interaction of a relativistic wind from a young pulsar with the wind fromits companion Be star. We assume the fast polar wind is clumpy, which istypical for radiatively-driven winds. The clumpiness cause the two winds tomix. The relativistic electrons from the pulsar wind are retained in the movingclumps by inhomogeneities of the magnetic field, which explains the X-rayvariability observed on time scales much shorter than the orbital period. Wecalculate detailed inhomogeneous spectral models reproducing the averagebroad-band spectrum from radio to TeVs. Given the uncertainties the form of thedistribution of relativistic electrons, the X-ray spectrum could be dominatedby either Compton or synchrotron emission. The recent Fermi observationsconstrain the high-energy cut-off in the electron distribution to be at theLorentz factor of 2 10^4 or 10^8 in the former and latter model, respectively.We provide formulae comparing the losses of the relativistic electrons due toCompton, synchrotron and Coulomb processes vs. the distance from the Be star.We calculate the optical depth of the wind to free-free absorption, showingthat it will suppress most of the radio emission within the orbit. We point outthe importance of Compton and Coulomb heating of the stellar wind within andaround the gamma-ray emitting region. Then, we find the most likely mechanismexplaining the orbital modulation at TeV energies is anisotropy of emission.

Author: A. A. Zdziarski, A. Neronov, M. Chernyakova

Source: https://arxiv.org/

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