The cooling of hot white dwarfs: a theory with non-standard weak interactions, and a comparison with observations

Abstract

We present calculations of the cooling evolutionary sequences of hot $$(T_{\rm eff}>12\times10^3 \ {\rm K})$$ white dwarf stars. The input physics is discussed in some detail, with special emphasis on the thermal conductivity and plasmon neutrino emission assumed. We suggest our own approximation for the latter. We find that the calculated effective temperature distribution of white dwarfs is rather sensitive to the assumed mass. The best fit to the observations yields the mass $$M=0.7 \ {\rm M}_{\odot}$$. With the inclusion of non-standard physics, we confirm the upper limit on the neutrino magnetic moment to be $$\mu_v <10^{-11}$$ in units of the Bohr magneton. Taking into account the bremsstrahlung of axions, we find a constraint on the axion–electron coupling (the axion fine-structure constant) of $$\alpha_{\rm a}<5\times10^{-26}$$.