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Time dependent magnetic fields can be sourced by spinning neutron stars, orbiting binaries and merging neutron stars. We consider electromagnetic radiation from axion condensates in the background of an alternating magnetic field. We find…

High Energy Physics - Phenomenology · Physics 2022-06-15 Srimoyee Sen , Lars Sivertsen

It has been suggested that radio telescopes may be sensitive to axion dark matter that resonantly converts to radio photons in the magnetospheres surrounding neutron stars (NSs). In this work, we closely examine this possibility by…

Cosmology and Nongalactic Astrophysics · Physics 2019-07-03 Benjamin R. Safdi , Zhiquan Sun , Alexander Y. Chen

We show that solar axion conversion to photons in the Earth's magnetosphere can produce an x-ray flux, with average energy \sim 4 keV, which is measurable on the dark side of the Earth. The smallness of the Earth's magnetic field is…

High Energy Physics - Phenomenology · Physics 2009-11-11 Hooman Davoudiasl , Patrick Huber

Magnetic field dependent transient solar observations are suggestive for axion-photon oscillations with light axion(-like) particle involvement. Novel dark-moon measurements with the SMART X-ray detectors can be conclusive for radiatively…

We discuss axion dark matter detection via two mechanisms: spontaneous decays and resonant conversion in neutron star magnetospheres. For decays, we show that the brightness temperature signal, rather than flux, is a less ambiguous measure…

Cosmology and Nongalactic Astrophysics · Physics 2020-07-15 Richard A. Battye , Bjoern Garbrecht , Jamie I. McDonald , Francesco Pace , Sankarshana Srinivasan

Axion dark matter (DM) may efficiently convert to photons in the magnetospheres of neutron stars (NSs), producing nearly monochromatic radio emission. This process is resonantly triggered when the plasma frequency induced by the underlying…

Cosmology and Nongalactic Astrophysics · Physics 2022-12-28 Joshua W. Foster , Samuel J. Witte , Matthew Lawson , Tim Linden , Vishal Gajjar , Christoph Weniger , Benjamin R. Safdi

Axions are hypothetical particles that could address both the strong charge-parity problem in quantum chromodynamics and the enigmatic nature of dark matter. However, if axions exist, their mass remains unknown, and they are expected to…

High Energy Physics - Phenomenology · Physics 2025-11-18 Evangelos Almpanis

Intense electric field $\sim 10^{10}-10^{11}$ V/cm in crystal has been known for a long time and has wide applications. We study the conversion of axion-like light particle and photon in the intense electric field in crystal. We find that…

High Energy Physics - Phenomenology · Physics 2011-07-22 Wei Liao

Recent work has shown that axions can be efficiently produced via non-stationary pair plasma discharges in the polar cap region of pulsars. Here, we point out that for axion masses $10^{-9} \, {\rm eV} \lesssim m_a \lesssim 10^{-4} \, \rm…

High Energy Physics - Phenomenology · Physics 2024-10-08 Dion Noordhuis , Anirudh Prabhu , Christoph Weniger , Samuel J. Witte

Thermally emitting neutron stars represent a promising environment for probing the properties of axion-like particles. Due to the strong magnetic fields of these sources, surface photons may partially convert into such particles in the…

High Energy Astrophysical Phenomena · Physics 2021-09-10 Aleksei Zhuravlev , Sergei Popov , Maxim Pshirkov

We identify a new resonance, axion magnetic resonance (AMR), that can greatly enhance the conversion rate between axions and photons. A series of axion search experiments rely on converting them into photons inside a constant magnetic field…

High Energy Physics - Phenomenology · Physics 2024-09-12 Hyeonseok Seong , Chen Sun , Seokhoon Yun

One of the promising new proposals to search for axions in astrophysical environments is to look for narrow radio lines produced from the resonant conversion of axion dark matter falling through the magnetospheres of neutron stars. For…

High Energy Physics - Phenomenology · Physics 2024-01-05 Jonas Tjemsland , Jamie McDonald , Samuel J. Witte

We investigate axion-photon conversion in stochastic magnetic fields, focusing on the evolution of the photon intensity and polarizations induced by conversion into axions. Assuming Gaussian magnetic fields characterized by the power…

High Energy Physics - Phenomenology · Physics 2025-12-25 Wataru Chiba , Ryusuke Jinno , Kimihiro Nomura

Axion clumps in an external magnetic field can emit electromagnetic radiation which causes them to decay. In the presence of a plasma, such radiation can become resonant if the clump frequency matches the plasma frequency. Typically, the…

High Energy Physics - Phenomenology · Physics 2023-03-29 Srimoyee Sen , Lars Sivertsen

Superradiance can cause the axion cloud around a rotating black hole to reach extremely high densities, and the decay of these axions can produce a powerful laser. The electric field of these lasers is strong enough that the Schwinger…

High Energy Physics - Phenomenology · Physics 2025-12-15 Bradley Shapiro

Axion dark matter can be converted into photons in the magnetospheres of neutron stars leading to a spectral line centred on the Compton wavelength of the axion. Due to the rotation of the star and the plasma effects in the magnetosphere…

Cosmology and Nongalactic Astrophysics · Physics 2023-11-29 R. A. Battye , M. J. Keith , J. I. McDonald , S. Srinivasan , B. W. Stappers , P. Weltevrede

We examine the resonant conversion of axion-like particle (ALP) or dark photon to the electromagnetic photon in the early Universe, which takes place due to the ALP-photon-dark photon oscillations in background dark photon gauge fields. It…

High Energy Physics - Phenomenology · Physics 2020-10-28 Kiwoon Choi , Hyeonseok Seong , Seokhoon Yun

Recently the EDGES experiment reported an enhanced 21cm absorption signal in the radio wave observation, which may be interpreted as either anomalous cooling of baryons or heating of cosmic microwave background photons. In this paper, we…

High Energy Physics - Phenomenology · Physics 2018-07-10 Takeo Moroi , Kazunori Nakayama , Yong Tang

The idea that photons can convert into axion-like particles (ALPs) $\gamma \to a$ in or around an AGN and reconvert back into photons $a \to \gamma$ in the Milky Way magnetic field has been put forward in 2008 and has recently attracted…

High Energy Astrophysical Phenomena · Physics 2015-05-20 Fabrizio Tavecchio , Marco Roncadelli , Giorgio Galanti

Relativistic axions are good candidates for the dark radiation for which there are mounting observational hints. The primordial decays of heavy fields produce axions which are ultra-energetic compared to thermalised matter and inelastic…

High Energy Physics - Phenomenology · Physics 2015-06-15 Joseph P. Conlon , M. C. David Marsh