A pulsational approach to the luminosity of Horizontal Branch stellar structures

Abstract

We discuss an alternative approach to constrain the absolute bolometric luminosity of Zero Age Horizontal Branch structures by using the observational pulsational properties of ab type RR Lyrae stars and theoretical expectations concerning both the relation connecting the pulsational properties of these variables to their evolutionary ones, as luminosity, mass and effective temperature and, also the location in the H-R diagram for the fundamental pulsators instability strip boundaries. Since the main goal of this work is to obtain an evaluation of the ZAHB bolometric luminosity as much as possible independent on stellar evolution theory, we have minimized the use of evolutionary prescriptions, being the only adopted evolutionary input the allowed mass range for fundamental pulsators. Nevertheless, the effects on our final results related to the use of these evolutionary prescriptions have been carefully checked. The reliability of the suggested method to obtain the ZAHB luminosity is shown by applying it to a selected sample of globular clusters (GCs), whose heavy elements abundance covers almost all the complete GCs metallicity range. The results obtained for the ZAHB bolometric luminosities have been compared with evolutionary prescriptions on such quite important quantity as given by recent evolutionary computations has been also performed. The existence of evident mismatches between current results and some evolutionary models has been verified and discussed.Comment: 15 pages, 1 table, 15 figures, postscript file, To be published in MNRA