Limits on axion properties from cooling of neutron stars

Cooling simulations of neutron stars and their comparison with the data from thermally emitting x-ray sources have been used for the first time to put constraints on the properties of axions, and by extension of any light pseudoscalar dark matter particles, whose existence has been postulated to solve the strong-CP problem of QCD, seeĀ https://arxiv.org/abs/1512.07828