skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SIGNATURES OF PHOTON-AXION CONVERSION IN THE THERMAL SPECTRA AND POLARIZATION OF NEUTRON STARS

Abstract

Conversion of photons into axions under the presence of a strong magnetic field can dim the radiation from magnetized astrophysical objects. Here we perform a detailed calculation aimed at quantifying the signatures of photon-axion conversion in the spectra, light curves, and polarization of neutron stars (NSs). We take into account the energy and angle dependence of the conversion probability and the surface thermal emission from NSs. The latter is computed from magnetized atmosphere models that include the effect of photon polarization mode conversion due to vacuum polarization. The resulting spectral models, inclusive of the general-relativistic effects of gravitational redshift and light deflection, allow us to make realistic predictions for the effects of photon to axion conversion on observed NS spectra, light curves, and polarization signals. We identify unique signatures of the conversion, such as an increase of the effective area of a hot spot as it rotates away from the observer line of sight. For a star emitting from the entire surface, the conversion produces apparent radii that are either larger or smaller (depending on axion mass and coupling strength) than the limits set by NS equations of state. For an emission region that is observed phase-on, photon-axion conversion resultsmore » in an inversion of the plane of polarization with respect to the no-conversion case. While the quantitative details of the features that we identify depend on NS properties (magnetic field strength and temperature) and axion parameters, the spectral and polarization signatures induced by photon-axion conversion are distinctive enough to make NSs very interesting and promising probes of axion physics.« less

Authors:
 [1];  [2]; ;  [3];  [4]
  1. JILA and Department of Astrophysical and Planetary Science, University of Colorado at Boulder, 440 UCB, Boulder, CO 80304 (United States)
  2. School of Mathematics, University of Southampton, Southampton, SO17 1BJ (United Kingdom)
  3. ICREA and ICC, University of Barcelona (IEEC-UB) (Spain)
  4. Center for Relativistic Astrophysics and School of Physics Georgia Institute of Technology, Atlanta, GA 30332 (United States)
Publication Date:
OSTI Identifier:
22016094
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 748; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; AXIONS; COSMOLOGY; EQUATIONS OF STATE; HOT SPOTS; MAGNETIC FIELDS; MODE CONVERSION; NEUTRON STARS; PHOTONS; POLARIZATION; RED SHIFT; RELATIVISTIC RANGE; STELLAR ATMOSPHERES; VACUUM POLARIZATION; X RADIATION

Citation Formats

Perna, Rosalba, Ho, Wynn C. G., Verde, Licia, Jimenez, Raul, and Van Adelsberg, Matthew. SIGNATURES OF PHOTON-AXION CONVERSION IN THE THERMAL SPECTRA AND POLARIZATION OF NEUTRON STARS. United States: N. p., 2012. Web. doi:10.1088/0004-637X/748/2/116.
Perna, Rosalba, Ho, Wynn C. G., Verde, Licia, Jimenez, Raul, & Van Adelsberg, Matthew. SIGNATURES OF PHOTON-AXION CONVERSION IN THE THERMAL SPECTRA AND POLARIZATION OF NEUTRON STARS. United States. https://doi.org/10.1088/0004-637X/748/2/116
Perna, Rosalba, Ho, Wynn C. G., Verde, Licia, Jimenez, Raul, and Van Adelsberg, Matthew. 2012. "SIGNATURES OF PHOTON-AXION CONVERSION IN THE THERMAL SPECTRA AND POLARIZATION OF NEUTRON STARS". United States. https://doi.org/10.1088/0004-637X/748/2/116.
@article{osti_22016094,
title = {SIGNATURES OF PHOTON-AXION CONVERSION IN THE THERMAL SPECTRA AND POLARIZATION OF NEUTRON STARS},
author = {Perna, Rosalba and Ho, Wynn C. G. and Verde, Licia and Jimenez, Raul and Van Adelsberg, Matthew},
abstractNote = {Conversion of photons into axions under the presence of a strong magnetic field can dim the radiation from magnetized astrophysical objects. Here we perform a detailed calculation aimed at quantifying the signatures of photon-axion conversion in the spectra, light curves, and polarization of neutron stars (NSs). We take into account the energy and angle dependence of the conversion probability and the surface thermal emission from NSs. The latter is computed from magnetized atmosphere models that include the effect of photon polarization mode conversion due to vacuum polarization. The resulting spectral models, inclusive of the general-relativistic effects of gravitational redshift and light deflection, allow us to make realistic predictions for the effects of photon to axion conversion on observed NS spectra, light curves, and polarization signals. We identify unique signatures of the conversion, such as an increase of the effective area of a hot spot as it rotates away from the observer line of sight. For a star emitting from the entire surface, the conversion produces apparent radii that are either larger or smaller (depending on axion mass and coupling strength) than the limits set by NS equations of state. For an emission region that is observed phase-on, photon-axion conversion results in an inversion of the plane of polarization with respect to the no-conversion case. While the quantitative details of the features that we identify depend on NS properties (magnetic field strength and temperature) and axion parameters, the spectral and polarization signatures induced by photon-axion conversion are distinctive enough to make NSs very interesting and promising probes of axion physics.},
doi = {10.1088/0004-637X/748/2/116},
url = {https://www.osti.gov/biblio/22016094}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 748,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2012},
month = {Sun Apr 01 00:00:00 EDT 2012}
}