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Title: Dynamical and Radiative Properties of X-Ray Pulsar Accretion Columns: Phase-averaged Spectra

Abstract

The availability of the unprecedented spectral resolution provided by modern X-ray observatories is opening up new areas for study involving the coupled formation of the continuum emission and the cyclotron absorption features in accretion-powered X-ray pulsar spectra. Previous research focusing on the dynamics and the associated formation of the observed spectra has largely been confined to the single-fluid model, in which the super-Eddington luminosity inside the column decelerates the flow to rest at the stellar surface, while the dynamical effect of gas pressure is ignored. In a companion paper, we have presented a detailed analysis of the hydrodynamic and thermodynamic structure of the accretion column obtained using a new self-consistent model that includes the effects of both gas and radiation pressures. In this paper, we explore the formation of the associated X-ray spectra using a rigorous photon transport equation that is consistent with the hydrodynamic and thermodynamic structure of the column. We use the new model to obtain phase-averaged spectra and partially occulted spectra for Her X-1, Cen X-3, and LMC X-4. We also use the new model to constrain the emission geometry, and compare the resulting parameters with those obtained using previously published models. Our model sheds new lightmore » on the structure of the column, the relationship between the ionized gas and the photons, the competition between diffusive and advective transport, and the magnitude of the energy-averaged cyclotron scattering cross-section.« less

Authors:
 [1];  [2];  [3]
  1. Department of Electrical and Computer Engineering, United States Naval Academy, Annapolis, MD (United States)
  2. Naval Research Laboratory (retired), Washington, DC (United States)
  3. Department of Physics and Astronomy, George Mason University, Fairfax, VA (United States)
Publication Date:
OSTI Identifier:
22663916
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; 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; ABSORPTION; ACCRETION DISKS; CROSS SECTIONS; CYCLOTRONS; EMISSION; HYDRODYNAMICS; LUMINOSITY; PHOTON TRANSPORT; PULSARS; RADIANT HEAT TRANSFER; RADIATION PRESSURE; RESOLUTION; SCATTERING; SHOCK WAVES; SURFACES; THERMODYNAMICS; TRANSPORT THEORY; VISIBLE RADIATION; X RADIATION; X-RAY SPECTRA

Citation Formats

West, Brent F., Wolfram, Kenneth D., and Becker, Peter A., E-mail: bwest@usna.edu, E-mail: kswolfram@gmail.com, E-mail: pbecker@gmu.edu. Dynamical and Radiative Properties of X-Ray Pulsar Accretion Columns: Phase-averaged Spectra. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/130.
West, Brent F., Wolfram, Kenneth D., & Becker, Peter A., E-mail: bwest@usna.edu, E-mail: kswolfram@gmail.com, E-mail: pbecker@gmu.edu. Dynamical and Radiative Properties of X-Ray Pulsar Accretion Columns: Phase-averaged Spectra. United States. doi:10.3847/1538-4357/835/2/130.
West, Brent F., Wolfram, Kenneth D., and Becker, Peter A., E-mail: bwest@usna.edu, E-mail: kswolfram@gmail.com, E-mail: pbecker@gmu.edu. Wed . "Dynamical and Radiative Properties of X-Ray Pulsar Accretion Columns: Phase-averaged Spectra". United States. doi:10.3847/1538-4357/835/2/130.
@article{osti_22663916,
title = {Dynamical and Radiative Properties of X-Ray Pulsar Accretion Columns: Phase-averaged Spectra},
author = {West, Brent F. and Wolfram, Kenneth D. and Becker, Peter A., E-mail: bwest@usna.edu, E-mail: kswolfram@gmail.com, E-mail: pbecker@gmu.edu},
abstractNote = {The availability of the unprecedented spectral resolution provided by modern X-ray observatories is opening up new areas for study involving the coupled formation of the continuum emission and the cyclotron absorption features in accretion-powered X-ray pulsar spectra. Previous research focusing on the dynamics and the associated formation of the observed spectra has largely been confined to the single-fluid model, in which the super-Eddington luminosity inside the column decelerates the flow to rest at the stellar surface, while the dynamical effect of gas pressure is ignored. In a companion paper, we have presented a detailed analysis of the hydrodynamic and thermodynamic structure of the accretion column obtained using a new self-consistent model that includes the effects of both gas and radiation pressures. In this paper, we explore the formation of the associated X-ray spectra using a rigorous photon transport equation that is consistent with the hydrodynamic and thermodynamic structure of the column. We use the new model to obtain phase-averaged spectra and partially occulted spectra for Her X-1, Cen X-3, and LMC X-4. We also use the new model to constrain the emission geometry, and compare the resulting parameters with those obtained using previously published models. Our model sheds new light on the structure of the column, the relationship between the ionized gas and the photons, the competition between diffusive and advective transport, and the magnitude of the energy-averaged cyclotron scattering cross-section.},
doi = {10.3847/1538-4357/835/2/130},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}