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Title: Constraining Relativistic Bow Shock Properties in Rotation-powered Millisecond Pulsar Binaries

Abstract

Multiwavelength follow-up of unidentified Fermi sources has vastly expanded the number of known galactic-field “black widow” and “redback” millisecond pulsar binaries. Focusing on their rotation-powered state, we interpret the radio to X-ray phenomenology in a consistent framework. We advocate the existence of two distinct modes differing in their intrabinary shock orientation, distinguished by the phase centering of the double-peaked X-ray orbital modulation originating from mildly relativistic Doppler boosting. By constructing a geometric model for radio eclipses, we constrain the shock geometry as functions of binary inclination and shock standoff R {sub 0}. We develop synthetic X-ray synchrotron orbital light curves and explore the model parameter space allowed by radio eclipse constraints applied on archetypal systems B1957+20 and J1023+0038. For B1957+20, from radio eclipses the standoff is R {sub 0} ∼ 0.15–0.3 fraction of binary separation from the companion center, depending on the orbit inclination. Constructed X-ray light curves for B1957+20 using these values are qualitatively consistent with those observed, and we find occultation of the shock by the companion as a minor influence, demanding significant Doppler factors to yield double peaks. For J1023+0038, radio eclipses imply R {sub 0} ≲ 0.4, while X-ray light curves suggest 0.1 ≲ R {submore » 0} ≲ 0.3 (from the pulsar). Degeneracies in the model parameter space encourage further development to include transport considerations. Generically, the spatial variation along the shock of the underlying electron power-law index should yield energy dependence in the shape of light curves, motivating future X-ray phase-resolved spectroscopic studies to probe the unknown physics of pulsar winds and relativistic shock acceleration therein.« less

Authors:
; ;  [1];  [2];  [3]
  1. Centre for Space Research, North–West University, Potchefstroom (South Africa)
  2. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  3. Department of Physics and Astronomy, Rice University, Houston, TX 77251 (United States)
Publication Date:
OSTI Identifier:
22663698
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 839; 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; ACCELERATION; ELECTRONS; ENERGY DEPENDENCE; INCLINATION; LIMITING VALUES; MODULATION; ORBITS; PULSARS; RELATIVISTIC RANGE; ROTATION; SHOCK WAVES; SPACE; STELLAR WINDS; VARIATIONS; VISIBLE RADIATION; X RADIATION

Citation Formats

Wadiasingh, Zorawar, Venter, Christo, Böttcher, Markus, Harding, Alice K., and Baring, Matthew G., E-mail: zwadiasingh@gmail.com. Constraining Relativistic Bow Shock Properties in Rotation-powered Millisecond Pulsar Binaries. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA69BF.
Wadiasingh, Zorawar, Venter, Christo, Böttcher, Markus, Harding, Alice K., & Baring, Matthew G., E-mail: zwadiasingh@gmail.com. Constraining Relativistic Bow Shock Properties in Rotation-powered Millisecond Pulsar Binaries. United States. doi:10.3847/1538-4357/AA69BF.
Wadiasingh, Zorawar, Venter, Christo, Böttcher, Markus, Harding, Alice K., and Baring, Matthew G., E-mail: zwadiasingh@gmail.com. Thu . "Constraining Relativistic Bow Shock Properties in Rotation-powered Millisecond Pulsar Binaries". United States. doi:10.3847/1538-4357/AA69BF.
@article{osti_22663698,
title = {Constraining Relativistic Bow Shock Properties in Rotation-powered Millisecond Pulsar Binaries},
author = {Wadiasingh, Zorawar and Venter, Christo and Böttcher, Markus and Harding, Alice K. and Baring, Matthew G., E-mail: zwadiasingh@gmail.com},
abstractNote = {Multiwavelength follow-up of unidentified Fermi sources has vastly expanded the number of known galactic-field “black widow” and “redback” millisecond pulsar binaries. Focusing on their rotation-powered state, we interpret the radio to X-ray phenomenology in a consistent framework. We advocate the existence of two distinct modes differing in their intrabinary shock orientation, distinguished by the phase centering of the double-peaked X-ray orbital modulation originating from mildly relativistic Doppler boosting. By constructing a geometric model for radio eclipses, we constrain the shock geometry as functions of binary inclination and shock standoff R {sub 0}. We develop synthetic X-ray synchrotron orbital light curves and explore the model parameter space allowed by radio eclipse constraints applied on archetypal systems B1957+20 and J1023+0038. For B1957+20, from radio eclipses the standoff is R {sub 0} ∼ 0.15–0.3 fraction of binary separation from the companion center, depending on the orbit inclination. Constructed X-ray light curves for B1957+20 using these values are qualitatively consistent with those observed, and we find occultation of the shock by the companion as a minor influence, demanding significant Doppler factors to yield double peaks. For J1023+0038, radio eclipses imply R {sub 0} ≲ 0.4, while X-ray light curves suggest 0.1 ≲ R {sub 0} ≲ 0.3 (from the pulsar). Degeneracies in the model parameter space encourage further development to include transport considerations. Generically, the spatial variation along the shock of the underlying electron power-law index should yield energy dependence in the shape of light curves, motivating future X-ray phase-resolved spectroscopic studies to probe the unknown physics of pulsar winds and relativistic shock acceleration therein.},
doi = {10.3847/1538-4357/AA69BF},
journal = {Astrophysical Journal},
number = 2,
volume = 839,
place = {United States},
year = {Thu Apr 20 00:00:00 EDT 2017},
month = {Thu Apr 20 00:00:00 EDT 2017}
}