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 energy^2,3. 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 horizoná-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.