STELLAR MASS-LUMINOSITY AND MASS-RADIUS RELATIONS

The new binary star data have been used together with new theoretical estimates in the study of mass-luminosity and mass-radius relations (MLR and MRR) for the Main-Sequence (MS) stars. The slopes of the relations change at certain critical values, e.g., at approximately 0.5 M. for MLR and at approximately 1.7 M. for MRR. The first point is the indication of transition from fully-convective internal structure to the developing radiative core, and the second point, the transition from proton-proton cycle to the carbon-nitrogen cycle as the dominant source of nuclear energy in these stars. It seems that these critical points are important in constraining on the stellar models. Improved set of more parameters for stars particularly around the critical points where the slopes of the relations change, may help bringing the theory and observations closer.