Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars

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dc.citation.articleNumber98
dc.citation.journalTitleThe Astrophysical Journal
dc.citation.volumeNumber854
dc.contributor.authorWadiasingh, Zorawar
dc.contributor.authorBaring, Matthew G.
dc.contributor.authorGonthier, Peter L.
dc.contributor.authorHarding, Alice K.
dc.date.accessioned2018-07-11T20:57:34Z
dc.date.available2018-07-11T20:57:34Z
dc.date.issued2018
dc.description.abstractHard, nonthermal, persistent pulsed X-ray emission extending between 10 and ~150 keV has been observed in nearly 10 magnetars. For inner-magnetospheric models of such emission, resonant inverse Compton scattering of soft thermal photons by ultrarelativistic charges is the most efficient production mechanism. We present angle-dependent upscattering spectra and pulsed intensity maps for uncooled, relativistic electrons injected in inner regions of magnetar magnetospheres, calculated using collisional integrals over field loops. Our computations employ a new formulation of the QED Compton scattering cross section in strong magnetic fields that is physically correct for treating important spin-dependent effects in the cyclotron resonance, thereby producing correct photon spectra. The spectral cutoff energies are sensitive to the choices of observer viewing geometry, electron Lorentz factor, and scattering kinematics. We find that electrons with energiesļ¾ lesssim15 MeV will emit most of their radiation below 250 keV, consistent with inferred turnovers for magnetar hard X-ray tails. More energetic electrons still emit mostly below 1 MeV, except for viewing perspectives sampling field-line tangents. Pulse profiles may be singly or doubly peaked dependent on viewing geometry, emission locale, and observed energy band. Magnetic pair production and photon splitting will attenuate spectra to hard X-ray energies, suppressing signals in theļ¾ Fermi-LAT band. The resonant Compton spectra are strongly polarized, suggesting that hard X-ray polarimetry instruments such as X-Calibur, or a future Compton telescope, can prove central to constraining model geometry and physics.
dc.identifier.citationWadiasingh, Zorawar, Baring, Matthew G., Gonthier, Peter L., et al.. "Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars." <i>The Astrophysical Journal,</i> 854, (2018) IOP Publishing: https://doi.org/10.3847/1538-4357/aaa460.
dc.identifier.doihttps://doi.org/10.3847/1538-4357/aaa460
dc.identifier.urihttps://hdl.handle.net/1911/102415
dc.language.isoeng
dc.publisherIOP Publishing
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
dc.titleResonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars
dc.typeJournal article
dc.type.dcmiText
dc.type.publicationpublisher version
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