Axion spectra and the associated x-ray spectra of low-mass stars

Abstract

For the first time, we predict the axion spectra and their associated luminosities for several low-mass stars -- one and two solar masses stars in the main sequence and post-main sequence stages of evolution. Equally, we also compute the x-ray excess emission resulting from the conversion of axions back to photons in the presence of a strong magnetic field in the envelope of these stars. Hence, a given star will have a unique axion spectrum and $L_a$ axion luminosity. And if such star has a strong magnetic field in its stellar envelope, it will also show a characteristic x-ray spectrum and $L_{a\gamma }$ x-ray luminosity. Such radiation will add up to the x-ray electromagnetic spectrum and $L_X$ luminosity of the star. The present study focuses on axion models with an axion-photon coupling constant, $510^{-11}{\mathrm{GeV}}^{-1}$, a value just below the most recent upper limit of $6.610^{-11}{\mathrm{GeV}}^{-1}$ found by CAST and IAXO helioscopes. The range of axion parameters discussed here spans many axion models' parameter space, including the DFSZ and KSVZ models. We found that axions with a mass in the range $10^{-7}$ to $10^{-5}\mathrm{eV}$ and an axion-photon coupling constant of $510^{-11}{\mathrm{GeV}}^{-1}$ produce an axion emission spectra with an averaged axion energy that varies from 1 to 5 KeV, and an $L_a$ ranging from $10^{-6}$ to $710^{-3}{L}_{\odot }$. We also predict that $L_{a\gamma }$ varies from $510^{-8}$ to $10^{-5}{L}_{\odot }$ for stars with an averaged magnetic field of $310^4\mathrm{G}$ in their atmospheres. Most of these $L_{a\gamma }$ predictions are larger than the $L_X$ observed in some stars. Therefore, such preliminary results show the potential of the next generation of stellar x-ray missions to constrain several classes of axion models.

12 pages, 1 table, 4 figures, published in PRD

References in corpus (21)

• Modules for Experiments in Stellar Astrophysics (MESA)
• The landscape of QCD axion models
• Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles
• The solar magnetic field
• Probing eV-scale axions with CAST
• Dilute and dense axion stars
• Stellar Recipes for Axion Hunters
• The connection between stellar activity cycles and magnetic field topology
• X-ray Searches for Axions from Super Star Clusters
• Magnetic Field Generation in Stars
• An X-ray activity cycle on the young solar-like star $\epsilon \mathrm{Eridani}$
• Revisiting longitudinal plasmon-axion conversion in external magnetic fields
• Axion helioscopes as solar magnetometers
• Future cosmological sensitivity for hot dark matter axions
• Hydrogen Axion Star: Metallic Hydrogen Bound to a QCD Axion BEC
• Inflection point in the power spectrum of stellar brightness variations. I. The model
• Production of axion-like particles from photon conversions in large-scale solar magnetic fields
• Oscillator models of the solar cycle: Towards the development of inversion methods
• A first proof of principle booster setup for the MADMAX dielectric haloscope
• The impact of composition choices on solar evolution: age, helio- and asteroseismology, and neutrinos
• Acoustic modes of pulsating axion stars: Non-radial oscillations

Cited by in corpus (1)

• Axion Astrophysics