No evidence for axions from Chandra observation of magnetic white dwarf

2021/04/26 by Christopher Dessert, Andrew J. Long, Benjamin R. Safdi · 3 citations
Physics and Astronomy · #astro-ph.HE #astro-ph.SR #hep-ph

paper · pdf · doi:10.1103/physrevlett.128.071102

7+11 pages, 4+7 figures

arxiv created 2021/04/26 · arxiv updated 2022/03/02

Abstract

Ultralight axions with axion-photon couplings g_aγγ ∼ \rm few × 10^-11 GeV^-1 may resolve a number of astrophysical anomalies, such as unexpected ~TeV transparency, anomalous stellar cooling, and X-ray excesses from nearby neutron stars. We show, however, that such axions are severely constrained by the non-observation of X-rays from the magnetic white dwarf (MWD) RE J0317-853 using ~40 ks of data acquired from a dedicated observation with the Chandra X-ray Observatory. Axions may be produced in the core of the MWD through electron bremsstrahlung and then convert to X-rays in the magnetosphere. The non-observation of X-rays constrains the axion-photon coupling to g_aγγ \lesssim 5.5 × 10^-13 √C_aγγ/C_aee GeV^-1 at 95% confidence for axion masses m_a \lesssim 5 × 10^-6 eV, with C_aee and C_aγγ the dimensionless coupling constants to electrons and photons. Considering that C_aee is generated from the renormalization group, our results robustly disfavor g_aγγ \gtrsim 4.4 × 10^-11 GeV^-1 even for models with no ultraviolet contribution to C_aee.

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