We propose a new approach to test possible corrections to Newtonian gravity using solar physics. The high accuracy of current solar models and new precise observations allow to constrain corrections to standard gravity at unprecedented levels. Our case study is Eddington-inspired gravity, an attractive modified theory of gravity which results in non-singular cosmology and collapse. The theory is equivalent to standard gravity in vacuum, but it sensibly differs from it within matter, for instance it affects the evolution and the equilibrium structure of the Sun, giving different core temperature profiles, deviations in the observed acoustic modes and in solar neutrino fluxes. Comparing the predictions from a modified solar model with observations, we constrain the coupling parameter of the theory, |κ g | 3 · 10 5 m 5 s −2 /kg. Our results show that the Sun can be used to efficiently constrain alternative theories of gravity.

We report the first constraints on the properties of weakly interacting low-mass dark matter (DM) particles using asteroseismology. The additional energy transport mechanism due to accumulated asymmetric DM particles modifies the central temperature and density of low-mass stars and suppresses the convective core expected in 1.1-1.3 M stars even for an environmental DM density as low as the expected in the solar neighborhood. An asteroseismic modeling of the stars KIC 8006161, HD 52265 and α Cen B revealed small frequency separations significantly deviated from the observations, leading to the exclusion of a region of the DM parameter space mass versus spin-dependent DM-proton scattering cross section comparable with present experimental constraints.

The formation and evolution of low-mass stars within dense halos of dark matter (DM) leads to evolution scenarios quite different from the classical stellar evolution. As a result of our detailed numerical work, we describe these new scenarios for a range of DM densities on the host halo, a range of scattering cross sections of the DM particles considered, and for stellar masses from 0.7 to 3 M ⊙ . For the first time, we also computed the evolution of young low-mass stars in their Hayashi track in the pre-main sequence phase and found that, for high DM densities, these stars stop their gravitational collapse before reaching the main sequence, in agreement with similar studies on first stars. Such stars remain indefinitely in an equilibrium state with lower effective temperatures (|∆T ef f | > 10 3 K for a star of one solar mass), the annihilation of captured DM particles in their core being the only source of energy. In the case of lower DM densities, these proto-stars continue their collapse and progress through the main sequence burning hydrogen at a lower rate. A star of 1 M ⊙ will spend a time greater than the current age of the universe consuming all the hydrogen in its core if it evolves in a halo with DM density ρ χ = 10 9 GeV cm −3 . We also show the strong dependence of the effective temperature and luminosity of these stars on the characteristics of the DM particles and how this can be used as an alternative method for DM research.

We studied the rate at which stars capture dark matter (DM) particles, considering different assumptions regarding the DM characteristics and, in particular, investigating how the stellar physics influences the capture rate. Two scenarios were considered: first, we assumed the maximal values for the spin-dependent and spin-independent DM particle-nucleon scattering cross sections allowed by the limits from direct detection experiments. Second, we considered that both scattering cross sections are of the same order, with the aim of studying the dependencies of the capture rate on stellar elements other than hydrogen. We found that the characteristics of the capture rate are very different in the two scenarios. Furthermore, we quantified the uncertainties on the computed capture rate (Cχ) and on the ratio between the luminosities from DM annihilations and thermonuclear reactions (Lχ/Lnuc) derived from an imprecise knowledge of the stellar structure and DM parameters. For instance, while an uncertainty of 10% on the typical DM velocity leads to similar errors on the computed Cχ and Lχ/Lnuc, the same uncertainty on the stellar mass becomes more relevant and duplicates the errors. Our results may be used to evaluate the reliability of the computed capture rate for the hypothetical use of stars other than the Sun as DM probes.PACS numbers: 95.35.+d, 97.10.-q

White dwarfs (WDs) are the most promising captors of dark matter (DM) particles in the crests that are expected to build up in the cores of dense stellar clusters. The DM particles could reach sufficient densities in WD cores to liberate energy through selfannihilation. The extinction associated with our Galactic Centre, the most promising region where to look for such effects, makes it impossible to detect the potential associated luminosity of the DM-burning WDs because due to distance and extreme extinction the apparent near-infrared magnitudes of the WDs would be fainter than about 30 mag. However, in smaller stellar systems which are close enough to us and not heavily extincted, such as ω−Cen, we may be able to detect DM-burning WDs. In this work we investigate the prospects of detection of DM-burning WDs in a stellar cluster harbouring an intermediate-mass black hole (IMBH), which leads to higher densities of DM at the centre as compared with clusters without one. We calculate the capture rate of WIMPs by a WD around an IMBH and estimate the luminosity that a WD would emit depending on its distance to the center of the cluster. Direct-summation N −body simulations of ω−Cen yield a non-negligible number of WDs in the range of radii of interest. We apply our assumption to published HST/ACS observations of stars in the center of ω−Cen to search for DM burning WDs and, although we are not able to identify any evident candidate because of crowding and incompleteness, we proof that their bunching up at high luminosities would be unique. We predict that DM burning will lead to a truncation of the cooling sequence at the faint end. The detection of DM burning in future observations of dense stellar clusters, such as globular clusters or ultra-compact dwarf galaxies could allow us to probe different models of DM distributions and characteristics such as the DM particle scattering cross section on nucleons. On the other hand, if DM-burning WDs really exist, their number and properties could give hints to the existence of IMBHs.