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Author Harding, Alice K. ♦ Kalapotharakos, Constantinos
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ DEPOLARIZATION ♦ FORECASTING ♦ GAMMA RADIATION ♦ HARD X RADIATION ♦ LIMITING VALUES ♦ MAGNETIC FIELDS ♦ PHOTON EMISSION ♦ PHOTONS ♦ POLARIZATION ♦ POSITRONS ♦ PULSARS ♦ RELATIVISTIC RANGE ♦ SYNCHROTRON RADIATION ♦ VISIBLE RADIATION
Abstract Polarization measurements provide strong constraints on models for emission from rotation-powered pulsars. We present multiwavelength polarization predictions showing that measurements over a range of frequencies can be particularly important for constraining the emission location, radiation mechanisms, and system geometry. The results assume a generic model for emission from the outer magnetosphere and current sheet in which optical to hard X-ray emission is produced by synchrotron radiation (SR) from electron–positron pairs and γ -ray emission is produced by curvature radiation (CR) or SR from accelerating primary electrons. The magnetic field structure of a force-free magnetosphere is assumed and the phase-resolved and phase-averaged polarization is calculated in the frame of an inertial observer. We find that large position angle (PA) swings and deep depolarization dips occur during the light-curve peaks in all energy bands. For synchrotron emission, the polarization characteristics are strongly dependent on photon emission radius with larger, nearly 180°, PA swings for emission outside the light cylinder (LC) as the line of sight crosses the current sheet. The phase-averaged polarization degree for SR is less that 10% and around 20% for emission starting inside and outside the LC, respectively, while the polarization degree for CR is much larger, up to 40%–60%. Observing a sharp increase in polarization degree and a change in PA at the transition between X-ray and γ -ray spectral components would indicate that CR is the γ -ray emission mechanism.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2017-05-10
Publisher Place United States
Journal Astrophysical Journal
Volume Number 840
Issue Number 2


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