Abstract
The evolution of white dwarfs is essentially a gravothermal process of cooling in which the basic ingredients for predicting their evolution are well identified, although not always well understood. There are two independent ways to test the cooling rate. One is the luminosity function of the white dwarf population, and another is the secular drift of the period of pulsation of those individuals that experience variations. Both scenarios are sensitive to the cooling or heating time scales, for which reason, the inclusion of any additional source or sink of energy will modify these properties and will allow to set bounds to these perturbations. These studies also require complete and statistical significant samples for which current large data surveys are providing an unprecedented wealth of information. In this paper we review how these techniques are applied to several cases like the secular drift of the Newton gravitational constant, neutrino magnetic moments, axions and weakly interacting massive particles (WIMPS).
Highlights
At present, the behavior of Nature is described with two fundamental theories
In any case it is possible to adjust the parameters of the Asymptotic Giant Branch (AGB) progenitors to obtain 20% of white dwarfs completely devoid of the hydrogen layer
Cheng et al, (2019) noticed that this overdensity is placed near the crystallization point of M ≳ 1 M⊙ and it cannot be accounted with the standard C/O model suggesting the gravitational settling of 22Ne as the extra source of energy necessary to introduce a substantial delay in the cooling of Ħ 8 Gyr
Summary
The behavior of Nature is described with two fundamental theories. One is the General Relativity (GR), which describes the gravitational interaction, the other is the Standard Model (SM), which describes the electromagnetic, weak and strong interactions. There are, two other independent ways to measure the cooling rate of WDs, one is based on the secular drift of the pulsation period of individual variables and the other on the shape of the luminosity function (Isern and García-Berro, 2008) These procedures have allowed to put bounds on the mass of axions (Raffelt, 1986; Isern et al, 1992, 2008), on the neutrino magnetic momentum (Blinnikov and Dunina-Barkovskaya, 1994), the secular drift of the Newton gravitational constant (Vila, 1976; García-Berro et al, 1995), the density of magnetic monopoles (Freese, 1984) and WIMPS (Bertone and Fairbairn, 2008), as well as constraints on properties of extra dimensions (Malec and Biesiada, 2001)), on dark forces (Dreiner et al, 2013), on modified gravity (Saltas et al, 2018), and formation of black holes by high energy collisions (Giddings and Mangano, 2008). The cases of the drift of the Newton constant, the magnetic momentum of neutrinos, axions and WIMPs will be discussed in this review
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