Limits on the neutrino magnetic dipole moment from the luminosity function of hot white dwarfs

M. M. MILLER BERTOLAMI

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2014 vol. 562 p. 123 - 131

0004-6361

Context. Recent determinations of the white dwarf luminosity function (WDLF) from very large surveys have extended our knowledgeof the WDLF to very high luminosities. This, together with the availability of new full evolutionary white dwarf models thatare reliable at high luminosities, have opened the possibility of testing particle emission in the core of very hot white dwarfs, whereneutrino processes are dominant.Aims. We use the available WDLFs from the Sloan Digital Sky Survey and the SuperCOSMOS Sky Survey to constrain the value ofthe neutrino magnetic dipole moment (μν).Methods. We used a state-of-the-art stellar evolution code to compute a grid of white dwarf cooling sequences under the assumptionsof different values of μν. Then we constructed theoretical WDLFs for different values of μν and performed a χ2-test to derive constraintson the value of μν.Results. We find that theWDLFs derived from the Sloan Digital Sky Survey and the SuperCOSMOS Sky Survey do not yield consistentresults. The discrepancy between the two WDLFs suggests that the uncertainties are significantly underestimated. Consequently,we constructed a unifiedWDLF by averaging the SDSS and SSS and estimated the uncertainties by taking into account the differencesbetween the WDLF at each magnitude bin. Then we compared all WDLFs with theoretical WDLFs. Comparison between theoreticalWDLFs and both the SDSS and the averaged WDLF indicates that μν should be μν < 5 × 10−12 e/(2mec). In particular, a χ2-test onthe averaged WDLF suggests that observations of the disk WDLF exclude values of μν > 5 × 10−12e/(2mec) at more than a 95%confidence level, even when conservative estimates of the uncertainties are adopted. This is close to the best available constraintson μν from the physics of globular clusters.Conclusions. Our study shows that modern WDLFs, which extend to the high-luminosity regime, are an excellent tool for constrainingthe emission of particles in the core of hot white dwarfs. However, discrepancies between different WDLFs suggest there mightbe some relevant unaccounted systematic errors. A larger set of completely independent WDLFs, as well as more detailed studies ofthe theoretical WDLFs and their own uncertainties, is desirable to explore the systematic uncertainties behind this constraint. Oncethis is done, we believe the Galactic disk WDLF will offer constraints on the magnetic dipole moment of the neutrino similar to thebest available constraints obtainable from globular clusters.