Neutrino Emissivities as a Probe of the Internal Magnetic Fields of White Dwarfs

Abstract

The evolution of white dwarfs (WDs) depends crucially on thermal processes. The plasma in their core can produce neutrinos which escape from the star, thus contributing to the energy loss. While in absence of a magnetic field the main cooling mechanism is plasmon decay at high temperature and photon surface emission at low temperature, a large magnetic field in the core hiding beneath the surface even of ordinary WDs, and undetectable to spectropolarimetric measurements, can potentially leave an imprint in the cooling. In this paper, we revisit the contribution to WD cooling stemming from neutrino pair synchrotron radiation and the effects of the magnetic field on plasmon decay. Our key finding is that even if observations limit the magnetic field strength at the stellar surface, magnetic fields in the interior of WDs -- with or without a surface magnetic field -- can be strong enough to modify the cooling rate, with neutrino pair synchrotron emission being the most important contribution. This effect may not only be relevant for the quantification and interpretation of cooling anomalies, but also suggests that the internal magnetic fields of WDs should be smaller than $\sim 6\times 10^{11}\mathrm{G}$, slightly improving bounds coming from a stability requirement. While our simplified treatment of the WD structure implies that further studies are needed to reduce the systematic uncertainties, the estimates based on comparing the emissivities illustrate the potential of neutrino emission as a diagnostic tool to study the interior of WDs.

21 pages, 6 figures. Matches published version

References in corpus (18)

• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• The landscape of QCD axion models
• Magnetic White Dwarfs
• White Dwarf Mass Distribution in the SDSS
• Feebly-Interacting Particles:FIPs 2020 Workshop Report
• Stellar Recipes for Axion Hunters
• Magnetic fields in isolated and interacting white dwarfs
• Constraining the neutrino magnetic dipole moment from white dwarf pulsations
• Strong limits on the DFSZ axion mass with G117-B15A
• No evidence for axions from Chandra observation of magnetic white dwarf
• Revisiting longitudinal plasmon-axion conversion in external magnetic fields
• Axion helioscopes as solar magnetometers
• The neutrino emission due to plasmon decay and neutrino luminosity of white dwarfs
• A Deep Proper Motion Catalog Within the Sloan Digital Sky Survey Footprint. II. The White Dwarf Luminosity Function
• Solar neutrino flux at keV energies
• Mass-radius relation of strongly magnetized white dwarfs: nearly independent of Landau quantization
• Effects of Magnetic Fields in Hot White Dwarfs

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