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Search for Axion-Like Particles in High-Magnetic-Field Pulsars with NICER

Yen-Jhen Liu, Yi Yang

TL;DR

This work probes photon–ALP conversion in pulsar magnetospheres using NICER X-ray spectra, targeting relativistic ALPs with a sliding-window power-law approach. Across three pulsars, no significant conversion features are found, leading to upper bounds on the axion–photon coupling $g_{a\gamma\gamma}$ in the range $10^{-12}$–$10^{-14}$ GeV$^{-1}$, with the strongest limit from PSR J2229+6114. The method combines robust windowing analyses and a physically motivated conversion probability in the $qL\ll 1$ regime, illustrating the potential of high-field astrophysical environments to constrain ALP parameter space in the relativistic regime. These results complement other astrophysical and laboratory searches, demonstrating NICER’s capability to contribute to ALP constraints in the X-ray band.

Abstract

Axion-like particles (ALPs) can couple to photons in strong magnetic fields, producing characteristic fluctuations in X-ray spectra. Using data from NASA's Neutron Star Interior Composition EXplorer (NICER), we analyzed three pulsars, PSR J2229+6114, PSR J1849-0001, and PSR B0531+21, to search for such features. Each spectrum was modeled with a sliding-window power-law fitting method to identify local deviations from the smooth continuum. From these analyses, we derived constraints on the axion-photon coupling constant $g_{aγγ}$ within a refined parameter space compared to previous studies, obtaining upper limits in the range $10^{-12}-10^{-14}GeV^{-1}$.

Search for Axion-Like Particles in High-Magnetic-Field Pulsars with NICER

TL;DR

This work probes photon–ALP conversion in pulsar magnetospheres using NICER X-ray spectra, targeting relativistic ALPs with a sliding-window power-law approach. Across three pulsars, no significant conversion features are found, leading to upper bounds on the axion–photon coupling in the range – GeV, with the strongest limit from PSR J2229+6114. The method combines robust windowing analyses and a physically motivated conversion probability in the regime, illustrating the potential of high-field astrophysical environments to constrain ALP parameter space in the relativistic regime. These results complement other astrophysical and laboratory searches, demonstrating NICER’s capability to contribute to ALP constraints in the X-ray band.

Abstract

Axion-like particles (ALPs) can couple to photons in strong magnetic fields, producing characteristic fluctuations in X-ray spectra. Using data from NASA's Neutron Star Interior Composition EXplorer (NICER), we analyzed three pulsars, PSR J2229+6114, PSR J1849-0001, and PSR B0531+21, to search for such features. Each spectrum was modeled with a sliding-window power-law fitting method to identify local deviations from the smooth continuum. From these analyses, we derived constraints on the axion-photon coupling constant within a refined parameter space compared to previous studies, obtaining upper limits in the range .

Paper Structure

This paper contains 6 sections, 8 equations, 2 figures, 1 table.

Table of Contents

  1. Introduction
  2. Data
  3. Analysis
  4. Result
  5. Conclusion
  6. Appendix

Figures (2)

  • Figure 1: The merged Pulsar spectrum for \ref{['fig:spectrum_1']} J2229+6114, \ref{['fig:spectrum_2']} J1849-0001, and \ref{['fig:spectrum_3']} B0531+21 with 3c50 background model subtraction, the colored band means the energy range we used to fit.
  • Figure 2: Axion-photon coupling constant constraints result from J2229+6114, J1849$-$0001 and B0531+21 pulsar spectra \ref{['fig:result_1']} for non-dark matter axion constraints and \ref{['fig:result_2']} for all dark matter constraints near X-ray range.