The dependence of the surface and interior characteristics of theoretical stellar models, evolved with variable G, on the age of the isochrone

The evolution of the surface and interior characteristics of theoretical stellar models, evolved under the assumption of the Brans-Dicke cosmology (decrease of the gravitational constant G with time), is discussed for models with the same mass in three isochrones (of one, three and five billion years of age). As the age of the isochrone increases the less massive models behave more and more like the more massive models of the isochrone of smaller age. The theoretical isochrones cannot be used as age indicators, at least not as freely as the ones received with constant G, since the position and shape of the isochrone for clusters of the same age and chemical composition also depends on the initial value of G as well as on the law of G variation. (author)