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Title: Multiwavelength Polarization of Rotation-powered Pulsars

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 tomore » 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.« less

Authors:
;  [1]
  1. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22663627
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 840; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 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

Citation Formats

Harding, Alice K., and Kalapotharakos, Constantinos. Multiwavelength Polarization of Rotation-powered Pulsars. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA6EAD.
Harding, Alice K., & Kalapotharakos, Constantinos. Multiwavelength Polarization of Rotation-powered Pulsars. United States. doi:10.3847/1538-4357/AA6EAD.
Harding, Alice K., and Kalapotharakos, Constantinos. Wed . "Multiwavelength Polarization of Rotation-powered Pulsars". United States. doi:10.3847/1538-4357/AA6EAD.
@article{osti_22663627,
title = {Multiwavelength Polarization of Rotation-powered Pulsars},
author = {Harding, Alice K. and Kalapotharakos, Constantinos},
abstractNote = {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.},
doi = {10.3847/1538-4357/AA6EAD},
journal = {Astrophysical Journal},
number = 2,
volume = 840,
place = {United States},
year = {Wed May 10 00:00:00 EDT 2017},
month = {Wed May 10 00:00:00 EDT 2017}
}