Green Bank and Effelsberg Radio Telescope Searches for Axion Dark Matter Conversion in Neutron Star Magnetospheres

Foster, Joshua W.; Kahn, Yonatan; Macías, Óscar; Zhan, Sun; Eatough, Ralph P.; Kondratiev, V. I.; Peters, Wendy; Weniger, Christoph; Safdi, Benjamin R.

doi:10.1103/physrevlett.125.171301

Cited by 96 publications

(80 citation statements)

References 53 publications

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“…Experimental constraints are shown in dark red and include the results from CAST [42] and dark matter axion haloscopes [16][17][18]22,25,27,28,31]. Astrophysical constraints are shown in green: the stellar bound from horizontal branch stars in globular clusters [114], and a recent indirect dark matter search with radio observations of neutron stars [115]. dependent.…”

Section: A Axion Mass Sensitivitymentioning

confidence: 99%

Axion helioscopes as solar magnetometers

et al. 2020

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Axion helioscopes search for solar axions and axionlike particles via inverse Primakoff conversion in strong laboratory magnets pointed at the Sun. Anticipating the detection of solar axions, we determine the potential for the planned next-generation helioscope, the International Axion Observatory (IAXO), to measure or constrain the solar magnetic field. To do this we consider a previously neglected component of the solar axion flux at sub-keV energies arising from the conversion of longitudinal plasmons. This flux is sensitively dependent to the magnetic field profile of the Sun, with lower energies corresponding to axions converting into photons at larger solar radii. If the detector technology eventually installed in IAXO has an energy resolution better than 200 eV, then solar axions could become an even more powerful messenger than neutrinos of the magnetic field in the core of the Sun. For energy resolutions better than 10 eV, IAXO could access the inner 70% of the Sun and begin to constrain the field at the tachocline: the boundary between the radiative and convective zones. The longitudinal plasmon flux from a toroidal magnetic field also has an additional 2% geometric modulation effect which could be used to measure the angular dependence of the magnetic field.

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Section: A Axion Mass Sensitivitymentioning

confidence: 99%

Axion helioscopes as solar magnetometers

et al. 2020

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“…Some of the strongest constraints on the coupling of axions to matter come from considering the production of axions in the hot and dense stellar interiors. Alternatively, if axions were produced in the early universe and survive today as dark matter, then the flux of these cold axions onto magnetized compact stars could result in a distinctive radio emission [58][59][60][61][62][63][64][65]. As much as an O(1) fraction of the axion dark matter could be in the form of axion stars, and therefore it is also important to develop strategies for detecting the encounter of axion stars with magnetized compact stars [66][67][68][69][70][71][72][73][74][75][76][77][78].…”

Section: Introductionmentioning

confidence: 99%

Dipole radiation and beyond from axion stars in electromagnetic fields

Amin

Long

Mou

et al. 2021

J. High Energ. Phys.

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We investigate the production of photons from coherently oscillating, spatially localized clumps of axionic fields (oscillons and axion stars) in the presence of external electromagnetic fields. We delineate different qualitative behaviour of the photon luminosity in terms of an effective dimensionless coupling parameter constructed out of the axion-photon coupling, and field amplitude, oscillation frequency and radius of the axion star. For small values of this dimensionless coupling, we provide a general analytic formula for the dipole radiation field and the photon luminosity per solid angle, including a strong dependence on the radius of the configuration. For moderate to large coupling, we report on a non-monotonic behavior of the luminosity with the coupling strength in the presence of external magnetic fields. After an initial rise in luminosity with the coupling strength, we see a suppression (by an order of magnitude or more compared to the dipole radiation approximation) at moderately large coupling. At sufficiently large coupling, we find a transition to a regime of exponential growth of the luminosity due to parametric resonance. We carry out 3+1 dimensional lattice simulations of axion electrodynamics, at small and large coupling, including non-perturbative effects of parametric resonance as well as backreaction effects when necessary. We also discuss medium (plasma) effects that lead to resonant axion to photon conversion, relevance of the coherence of the soliton, and implications of our results in astrophysical and cosmological settings.

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“…As a consequence of this inconsistency, new bounds on the parameter space of ALPs are inferred by taking as reference the magnetic field associated with two pulsars: SGR 1806-20 [57,58,[77][78][79] and RX J1856.5-3754 [80][81][82][83][84][85][86]. We shall mention at this point that considerable attention is currently paid to the possibility of probing ALPs via observational effects induced by them in neutron star magnetospheres [87][88][89][90].…”

Section: Introductionmentioning

confidence: 99%

Magnetic dominance of axion electrodynamics: photon capture effect and anisotropy of Coulomb potential

2021

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For magnetic fields larger than the characteristic scale linked to axion-electrodynamics, quantum vacuum fluctuations due to axion-like fields can dominate over those associated with the electron-positron fields. This conjecture is explored by investigating both the axion-modified photon capture by a strong magnetic field and the Coulomb potential of a static pointlike charge. We show that in magnetic fields characteristic of neutron stars $$\sim 10^{13}$$ ∼ 10 13 –$$10^{15}\;\mathrm{G}$$ 10 15 G , the capture of gamma photons prior to the production of a pair can prevent the existence of an electron-positron plasma, essential for explaining the pulsar radiation mechanism. This incompatibility is used to limit the axion parameter space. Our bounds improve existing outcomes in the region of mass $$m\sim 10^{-10}$$ m ∼ 10 - 10 –$$10^{-5}\;{\mathrm{eV}}$$ 10 - 5 eV . The effect of capture, known in QED as relating to gamma-quanta, is extended in axion electrodynamics to include X-ray photons with the result that a specially polarized part of the heat radiation from the surface is canalized along the magnetic field. Besides, we find that in the regime in which the dominance takes place, the running QED coupling depends on the field strength and the modified Coulomb potential is of Yukawa-type in the direction perpendicular to the magnetic field at distances much smaller than the axion Compton wavelength, while along the field it follows approximately the Coulomb law at any length scale. Despite the Coulomb singularity manifested in the latter case, we argue that the ground-state energy of a non-relativistic hydrogen atom placed in a strong magnetic field turns out to be bounded due to the nonrenormalizable feature of axion-electrodynamics.

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Green Bank and Effelsberg Radio Telescope Searches for Axion Dark Matter Conversion in Neutron Star Magnetospheres

Cited by 96 publications

References 53 publications

Axion helioscopes as solar magnetometers

Axion helioscopes as solar magnetometers

Dipole radiation and beyond from axion stars in electromagnetic fields

Magnetic dominance of axion electrodynamics: photon capture effect and anisotropy of Coulomb potential

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