Constraining Neutrino Cooling using the Hot White Dwarf Luminosity Function in the Globular Cluster 47 Tucanae

TL;DR

This study uses Hubble data of hot white dwarfs in 47 Tucanae to refine neutrino emission estimates and constrain exotic physics like axions and extra dimensions.

Contribution

It provides the first luminosity function of hot white dwarfs in 47 Tucanae and constrains neutrino emission and exotic particle mechanisms.

Findings

No high-temperature plateau in white dwarf luminosity function.

Neutrino emission estimates are accurate within a factor of two.

Limits placed on axions, neutrino magnetic moments, and extra dimensions.

Abstract

We present Hubble Space Telescope observations of the upper part (T_eff> 10 000 K) of the white dwarf cooling sequence in the globular cluster 47 Tucanae and measure a luminosity function of hot white dwarfs. Comparison with previous determinations from large scale field surveys indicates that the previously determined plateau at high effective temperatures is likely a selection effect, as no such feature is seen in this sample. Comparison with theoretical models suggests that the current estimates of white dwarf neutrino emission (primarily by the plasmon channel) are accurate, and variations are restricted to no more than a factor of two globally, at 95% confidence. We use these constraints to place limits on various proposed exotic emission mechanisms, including a non-zero neutrino magnetic moment, formation of axions, and emission of Kaluza-Klein modes into extra dimensions.