Core-Halo Structure of a Chemically Homogeneous Massive Star and Bending of the Zero-Age Main Sequence

摘要

WehaverecalculatedtheinteriorstructureofverymassivestarsofuniformchemicalcompositionwiththeOPALopacity.Verymassivestarsarefoundtodevelopacore-halostructurewithanextendedradiative-envelope.Withthecore-halostructure,becauseamoremassivestarhasamoreextendedenvelope,thetrackoftheupperzero-agemain-sequence(ZAMS)curvesredwardintheH-Rdiagramat100M??(Z=0.02),70Af??(Z=0.05),and15M??forheliumZAMS(X=0,Z=0.02).Therefore,theeffectivetemperaturesofverymassiveZAMSstarsareratherlow:e.g.,fora200M??star,logTeff=4.75(Z=0.004),4.60(Z=0.02),4.46(Z=0.05),and4.32(Z=0.10).Theeffectivetemperaturesofveryluminousstars(120M??)foundintheLMC,theSMC,andtheGalaxyarediscussedinrelationtothismetaldependenceofacurvinguppermain-sequence.