White dwarfs as a probe of dark energy

Abstract

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 barotropic equation of state which has three free parameters (density, equation of state and effective sound speed) is used. We analyse 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 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. Obtained distribution is used to find the parameters of dark energy for which the deviation from the Chandrasekhar model massradius relation become non-negligible. We conclude also, that the absence of observational evidence for existence of WDs with untypical intrinsic structure (mass-radius relation) gives us lower limit for the value of effective sound speed of dark energy c 2 s 10 −4 (in units of speed of light).

Non-accelerator particle physics in Ukraine

“…Теоретичні дослідження темної матерії і темної енергії ведуться в Астрономічній обсерваторії Львівського національного університету імені Івана Франка. Учені Обсерваторії досліджують вплив динамічної темної енергії на рівновагу нейтронних зір [25,26], отримали обмеження на параметри темної енергії на основі космологічних даних про реліктове випромінювання, баріонні акустичні осциляції видимої матерії у Всесвіті та наднові зорі типу I a [27][28][29].…”

Impact of dynamical dark energy on the neutron star equilibrium

“…Then we re-evaluated the distribution of dark energy and baryonic matter in the new potential. Such procedure was repeated until the solutions converged or the iteration limit exceeded (for more details see [7]). The solutions of the system of equations (3.4-3.5) for the dark energy component are shown in Fig.…”

“…The local behavior of the perturbed dark energy has become an object of study in a series of works of the last decade. The impact of perturbation and clusterization of dark energy on the matter dynamics was studied on clusters of galaxies and galaxy scales (for example, in [1][2][3][4]) and on the astrophysical scale ( [5][6][7][8][9][10][11][12][13][14]). In general, studies have shown, that the local impact of minimally coupled perturbed dark energy is mostly negligible, except some specific value regions of its parameters space, which can be used for ruling out these values.…”

“…We studied the static solutions of dark energy dynamical equations in the vicinity of compact objects and found that only relativistic objects with the lowest ratio "radius to gravitational radius" disturb the density of dynamical dark energy noticeably [6]. In the paper [7] we have investigated how the dynamical dark energy inside white dwarfs can change their mass-radius relation and have found that the squared effective speed of sound c 2 s of dark energy must be larger than ∼ 5 • 10 −4 in order to satisfy the observed mass-radius relation for white dwarfs. In the paper [8], we have used the uncertainty of determination of gravitating mass in the Solar system as an upper limit on the amount of clustered dark energy and obtained the similar constraints for the value of c 2 s ≥ 2 • 10 −4 .…”

Dark Sector in Cosmology: Dark Energy on Cosmological and Astrophysical Scales

“…The ability of dynamic dark energy with 2 ≪ 1 to change the shape and depth of the gravitational potential well of the compact stellar objects has been used in [40,41] to establish the lower limit for the effective sound speed of dark energy on the basis of the accuracies of the elements of the orbits of all bodies in the Solar system within the orbit of Saturn, as well as the Chandrasekhar mass-radius relation for white dwarfs. Both approaches indicate that the effective speed of sound of dark energy is greater than 10 −4 in the units of the speed of light.…”