Abstract
The white dwarf luminosity function, which provides information about their cooling, has been measured with high precision in the past few years. Simulations that include well known Standard Model physics give a good fit to the data. This leaves little room for new physics and makes these astrophysical objects a good laboratory for testing models beyond the Standard Model. It has already been suggested that white dwarfs might provide some evidence for the existence of axions. In this work we study the constraints that the white dwarf luminosity function puts on physics beyond the Standard Model involving new light particles (fermions or bosons) that can be pair-produced in a white dwarf and then escape to contribute to its cooling. We show, in particular, that we can severely constrain the parameter space of models with dark forces and light hidden sectors (lighter than a few tens of keV). The bounds we find are often more competitive than those from current lab searches and those expected from most future searches.
Highlights
White dwarfs (WDs) are simple astrophysical objects whose cooling law is well understood
Following [1] the bound from red giants (RGs) cooling can be translated into Sx 2, which corresponds to CxGx 1.41CV GF and is comparable to, but slightly weaker than what we found in Eq (3.8) for WDs
Given that we are interested in masses below a few tens of keV, if they were in thermal equilibrium with ordinary matter in the early universe until big bang nucleosynthesis (BBN), that happens at T ∼ 1 MeV, they would contribute to the number of relativistic degrees of freedom, which is well constrained
Summary
White dwarfs (WDs) are simple astrophysical objects whose cooling law is well understood. This fact makes them a good laboratory for testing new models of particle physics. The first term on the r.h.s. is the well known contribution of the heat capacity of the star to the total luminosity, the second one represents the contribution of the change of volume. When neutrinos are included and the cooling is simulated with a full stellar evolution code the agreement becomes impressive (see the continuous lines of Fig. 1) This agreement can be used to bound the inclusion of new sources or sinks of energy [3]
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