No Evidence for Axions from Chandra Observation of the Magnetic White Dwarf RE J0317-853

• Published in: Physical review letters 2022-02, Vol.128 (7), p.071102-071102, Article 071102
• Main Authors: Dessert, Christopher, Long, Andrew J, Safdi, Benjamin R
• Format: Article
• Language: English
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.128.071102

Axions with couplings g_{aγγ}∼few×10^{-11}  GeV^{-1} to electromagnetism 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 nonobservation 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 nonobservation of x rays constrains the axion-photon coupling to g_{aγγ}≲5.5×10^{-13}sqrt[C_{aγγ}/C_{aee}]  GeV^{-1} at 95% confidence for axion masses m_{a}≲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}≳4.4×10^{-11}  GeV^{-1} even for models with no ultraviolet contribution to C_{aee}.