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

Abstract

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

A young contracting white dwarf in the peculiar binary HD 49798/RX J0648.0–4418 ?

“…This is supported by recent works in which a similar technique is used to constrain the neutrino emission of hot WDs., e.g. (Miller Bertolami 2014;Hansen et al 2015), and references therein.…”

Pulsating white dwarfs: new insights

“…One approach considers WD models characterized by parameterized chemical composition profiles, while the other technique involves fully evolutionary models constructed with chemical profiles resulting from all the processes experienced during the evolution of the WD progenitors. The former approach constitutes a powerful forward method with the flexibility of allowing a full exploration of the parameter space (the total mass, the mass of the H and He envelopes, the thickness of the chemical transition regions, the core chemical structure and composition, etc) to find an optimum asteroseismological solution (see Bradley, 1998Bradley, , 2001Bischoff-Kim et al, 2008a, 2014, 2019Fu et al, 2013;Bognár et al, 2016;Giammichele et al, 2017a,b, among others). In particular, Giammichele et al (2017a,b) present a new prescription for parameterizing the chemical profiles in the core of WDs which is based on Akima splines.…”

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

“…Most directly, it represents a factor of several improvement of earlier determinations µ 12 < 10 based on the hot white dwarf luminosity function (Blinnikov & Dunina-Barkovskaya 1994). Although measurements of the hot white dwarf luminosity function have improved since then, the excess counts at the bright end (see discussion in § 3.1) have hampered the statistical significance of such constraints using the more up-to-date data (Miller Bertolami 2014). Our measurement is also comparable to the limits derived from the core mass of red giant stars (Castellani & degl'Innocenti 1993;Catelan et al 1996;Haft et al 1994;Raffelt 1990;Raffelt & Weiss 1992;Viaux et al 2013) but has the advantage of being measured in stars whose properties are dominated by the neutrino emission and in a manner in which the distance (the largest source of error in the red giant measurements) is constrained simultaneously.…”