Q-nucleosynthesis: implications for stellar evolution

The effects on stellar burning of anomalous nuclei (Q-nuclei) containing an extra embedded quark were investigated using a modified version the Paczynski stellar evolution code. A series of solar models were constructed for a range in Q-nuclear abundance and the results compared with the predictions of the standard solar model and observed solar parameters. With a Q-nuclear abundance of approximately 5 x 10-15 Q-nuclei per normal nucleus, several outstanding discrepancies between theoretical predictions of the standard solar model and relevant observations are alleviated including the solar neutrino problem. In an attempt to ascertain whether or not the abundance of Q-nuclei suggested by solar model calculations is compatible with the observed properties of main sequence stars, zero-age main-sequence models were constructed with and without Q-nuclear burning. Q-nucleosynthesis drives down the luminosity and increases the stellar radius resulting in a substantial decrease in surface temperature for stars with masses greater than about one solar mass. A comparison of the published observations of the Pleiades and the predicted location of the Q-nuclear burning main sequence precludes an abundance of Q-nuclei greater than about 2 x 10-16 at the present epoch. It is suggested, however, that nuclear-burning processes may selectively destroy the lighter Q-nuclei, so that their abundance in the interstellar medium would decrease with time