Stellar convective cores as dark matter probes

The recent detection of a convective core in a main-sequence solar-type star is used here to test particular models of dark matter (DM) particles, those with masses and scattering cross sections in the range of interest for the DM interpretation of the positive results in several DM direct detection experiments. If DM particles do not effectively self annihilate after accumulating inside low-mass stars (e.g. in the asymmetric DM scenario) their conduction provides an efficient mechanism of energy transport in the stellar core. For main-sequence stars with masses between 1.1 and $1.3{\mathrm{M}}_{\odot }$, this mechanism may lead to the suppression of the inner convective region expected to be present in standard stellar evolution theory. The asteroseismic analysis of the acoustic oscillations of a star can prove the presence/absence of such a convective core, as it was demonstrated for the first time with the Kepler field main-sequence solarlike pulsator, KIC 2009505. Studying this star we found that the asymmetric DM interpretation of the results in the CoGeNT experiment is incompatible with the confirmed presence of a small convective core in KIC 2009505.

Figure 1

(a) Temperature, (b) hydrogen abundance in mass fraction, and (c) adiabatic sound-speed profiles for representative models of Dushera with a convective core at $R_{\text{cc}}=0.07{\mathrm{R}}_{\star }$ (black continuous line, corresponding to a model not influenced by DM) and without it (blue dashed line, corresponding to a model strongly impacted by DM conduction).

Figure 2

Distribution of the radii of the convective core, $R_{\text{cc}}$, in all the computed models that reproduce the observations of the star Dushera, in the standard scenario without DM (grey) and including the impact of different DM models (colors; see text). The shapes of the distributions (violin plots) show the probability density, and the internal discontinuous lines correspond to the first quartile, the median and the third quartile. The yellow area shows the range of the $R_{\text{cc}}$ inferred for Dushera in Ref. [46].

Figure 3

Distribution of the asteroseismic parameter $|S\{\mathrm{\Delta }\nu r_{010}\}|$ in all the computed models that reproduce the observations of the star Dushera, in the standard scenario without DM (grey) and including the impact of different DM models (colors; see text). The shapes of the distributions (violin plots) show the probability density, and the internal discontinuous lines correspond to the first quartile, the median and the third quartile. The yellow area shows the value of $|S\{\mathrm{\Delta }\nu r_{010}\}|$ calculated from the observed frequencies with its uncertainty.