Dark matter and the age of globular clusters

Abstract

GALACTIC dark matter may consist of weakly interacting particles which can be captured and trapped in stars1, and which would then contribute to the transfer of energy2,3. A special class of these particles ('cosmions'), with weak cross-sections that are larger than standard has been invoked as a solution of the solar-neutrino problem, and also as a means of suppressing convection in the cores of horizontal-branch stars4. Here we investigate this latter effect numerically and find that the convection breaking in horizona-tal-branch stars by cosmions, or by any other novel mode of energy transfer, induces thermal relaxation oscillations with a period of ∼5xl05yr, corresponding to the core Kelvin-Helmholtz time-scale. These thermal pulses can be understood analytically in terms of a simple two-zone model. Observationally, the brightness and brightness dispersion of horizontal-branch stars increases, the periods of RR Lyrae stars change over a pulsation timescale, and the duration of central helium burning slightly decreases. None of these effects is in conflict with observations, but, on the contrary, point to a speculative resolution of the age problem for globular clusters and to an alternative explanation of the period fluctuations of RR Lyrae stars.