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

Axions with couplings g(a gamma gamma) similar to few x 10(-11) GeV-1 to electromagnetism may resolve a number of astrophysical anomalies, such as unexpected similar to 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 similar to 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(a gamma gamma) less than or similar to 5.5 x 10(-13) root C-a gamma gamma/C-a gamma gamma GeV-1 at 95% confidence for axion masses m(a) less than or similar to 5 x 10(-6) eV, with C-aee and C-a gamma gamma the dimensionless coupling constants to electrons and photons. Considering that C-aee is generated from the renormalization group, our results robustly disfavor g(a gamma gamma) greater than or similar to 4.4 x 10(-11) GeV-1 even for models with no ultraviolet contribution to C-aee.

Automated summary

Axions with electromagnetic-like couplings at a level around few x 10(-11) GeV-1 may address some astrophysical anomalies, but the non-observation of X-rays from a magnetic white dwarf severely constrains the axion-photon coupling.