White dwarfs as a probe of dark energy

We investigate the radial density distribution of the dynamical dark energy inside the white dwarfs (WDs) and its possible impact on their intrinsic structure. The minimally coupled dark energy with the barotropic equation of state, which has three free parameters (density, equation of state, and effective sound speed), is used. We analyze how such dark energy affects the mass-radius relation for the WDs because of its contribution to the joint gravitational potential of the system. For this we use the Chandrasekhar model of the WDs, where model parameters are the parameter of the chemical composition and the relativistic parameter. To evaluate the dark energy distribution inside a WD we solve the conservation equation in the spherical static metric. The obtained distribution is used to find the parameters of dark energy for which the deviation from the Chandrasekhar model mass-radius relation become non-negligible. We conclude also that the absence of observational evidence for the existence of WDs with untypical intrinsic structure (mass-radius relation) gives us lower limits for the value of an effective sound speed of dark energy c_s²≳10^-4 (in units of speed of light).