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Probing Axions with Event Horizon Telescope Polarimetric Measurements

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arxiv 1905.02213 v2 pith:4GDEBSFY submitted 2019-05-06 hep-ph astro-ph.COgr-qc

Probing Axions with Event Horizon Telescope Polarimetric Measurements

classification hep-ph astro-ph.COgr-qc
keywords staraxionaxionsblackhorizonaroundeventhole
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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With high spatial resolution, polarimetric imaging of a supermassive black hole, like M87$^\star$ or Sgr A$^\star$, by the Event Horizon Telescope can be used to probe the existence of ultralight bosonic particles, such as axions. Such particles can accumulate around a rotating black hole through the superradiance mechanism, forming an axion cloud. When linearly polarized photons are emitted from an accretion disk near the horizon, their position angles oscillate due to the birefringent effect when traveling through the axion background. In particular, the observations of supermassive black holes M87$^\star$ (Sgr A$^\star$) can probe the dimensionless axion-photon coupling $c = 2 \pi g_{a \gamma} f_a$ for axions with mass around $O(10^{-20})$~eV ($O( 10^{-17}$)~eV) and decay constant $f_a < O(10^{16})$ GeV, which is complimentary to other axion measurements.

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Cited by 7 Pith papers

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