Secondary-electron radiation from SNRs

Posted on | In
The synchrotron radiation from secondary electrons and positrons (SEPs) generated by hadronic interactions in the shock of supernova remnant (SNR) could be a distinct evidence of cosmic ray (CR) production in SNR shocks. Here we provide a method where the observed gamma-ray flux from SNRs, created by pion decays, is directly used to derive the SEP distribution and hence the synchrotron spectrum. We apply the method to three gamma-ray bright SNRs, RX J1713.7-3946, IC 443 and W44.

Y., Li Z., Wang W., Zhao X., 2018, arXiv, arXiv:1807.11239, to be submitted.
Full Paper: https://arxiv.org/

The synchrotron radiation from secondary electrons and positrons (SEPs) generated by hadronic interactions in the shock of supernova remnant (SNR) could be a distinct evidence of cosmic ray (CR) production in SNR shocks. Here we provide a method where the observed gamma-ray flux from SNRs, created by pion decays, is directly used to derive the SEP distribution and hence the synchrotron spectrum. We apply the method to three gamma-ray bright SNRs, RX J1713.7-3946, IC 443 and W44.

  • In the young SNR RX J1713.7-3946, if the observed GeV-TeV gamma-rays are of hadronic origin and the magnetic field in the SNR shock is B>0.5mG, the SEPs may produce a spectral bump at 1E-5 - 1E-2 eV, exceeding the predicted synchrotron component of the leptonic model, and a soft spectral tail at >100keV, distinct from the hard spectral slope in the leptonic model.

  • In the middle-aged SNRs IC 443 and W44, if the observed gamma-rays are of hadronic origin, the SEP synchrotron radiation with B~0.3-0.4mG can well account for the observed radio flux and spectral slopes, supporting the hadronic origin of gamma-rays.

  • Future microwave to far-infrared and hard X-ray (>100keV) observations are encouraged to constraining the SEP radiation and the gamma-ray origin in SNRs.