Supernova progenitor stars in the initial range of 23 to?33 solar masses and their relation with the SNR?Cassiopeia?A

摘要

Context. Multi wavelength observations of Cassiopeia A (Cas A)have provided us with strong evidence of circumstellar materialsurrounding the progenitor star. It has been suggested that itsprogenitor was a massive star with strong mass loss. But, despite thelarge amount of observational data from optical, IR, radio, and x-rayobservations, the identity of CasA progenitor is still elusive. Aims. In this work, we computed stellar and circumstellarnumerical models to look for the progenitor of CasA. The modelsare compared with the observational constraints that come from chemicalobserved abundances and dynamical information. Methods. We first computed stellar evolution models to gettime-dependent wind parameters and surface abundances using the codeSTERN. To explore the range of masses proposed by several previousworks, we chose a set of probable progenitor stars with initial massesof23, 28, 29, 30, and 33,with initial solar composition (Y=0.28, Z=0.02)and mass loss. The derived mass loss rates and wind terminal velocitiesare used as inner boundary conditions in the explicit, hydrodynamicalcode ZEUS-3D to simulate the evolution of the circumstellar medium. Wesimplified the calculations by using one-dimensional grids in the mainsequence and red super-giant (RSG) stages, and two-dimensional gridsfor the post-RSG evolution and supernova (SN) blast wave. Results. Our stellar set gives distinct SN progenitors: RSG,luminous blue super giants (LBSGs), and Wolf-Rayet (WR) stars. We namedthese type of stars ``luminous blue super giant'' (LBSGs) todistinguish them from normal blue super giants (BSGs) of much lowerinitial masses. The 23star explodes as an RSG in a dense, free-streaming wind surrounded by a thin, compressed, RSG shell. The 28star explodes as an LBSG, and the SN blast wave interacts with a lowdensity, free streaming wind surrounded by an unstable and massive``RSG+LBSG'' shell. Finally, the30 and 33stars explode as WRstars surrounded by fast WR winds thatterminate in a highly fragmented ``WR+RSG shell''. We compared thesurface chemical abundances of our stellar models with theobservational abundances in CasA. The abundance analysis showsthat the progenitor was a star with an initial mass of about 30,while the hydrodynamical analysis favors progenitors with initial masses around23. Key words: stars: evolution - ISM: kinematics and dynamics - ISM: supernova remnants - ISM: bubbles - ISM: individual objects: Cassiopeia A