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Hard Spectral Tails in Magnetars

Published online by Cambridge University Press:  04 June 2018

Zorawar Wadiasingh ,
Matthew G. Baring ,
Peter L. Gonthier  and
Alice K. Harding
Zorawar Wadiasingh
Affiliation:
Centre For Space Research, North-West University, Potchefstroom, South Africa
Matthew G. Baring
Affiliation:
Rice University, Houston, Texas, USA
Peter L. Gonthier
Affiliation:
Hope College, Holland, Michigan, USA
Alice K. Harding
Affiliation:
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
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Abstract

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Pulsed non-thermal quiescent emission between 10 keV and around 150 keV has been observed in ~10 magnetars. For inner magnetospheric models of such hard X-ray signals, resonant Compton upscattering of soft thermal photons from the neutron star surface is the most efficient radiative process. We present angle-dependent hard X-ray upscattering model spectra for uncooled monoenergetic relativistic electrons. The spectral cut-off energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the observed turnovers in magnetar hard X-ray tails. Moreover, electrons of higher energy still emit most of the radiation below around 1 MeV, except for quasi-equatorial emission locales for select pulses phases. Our spectral computations use new state-of-the-art, spin-dependent formalism for the QED Compton scattering cross section in strong magnetic fields.

Keywords

radiation mechanisms: non-thermal–magnetic fields–stars: neutron–pulsars: general–X rays: theory
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S337: Pulsar Astrophysics the Next Fifty Years , September 2017 , pp. 108 - 111
Copyright
Copyright © International Astronomical Union 2018 

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