Supernova progenitor stars in the initial range of 23 to 33 solarmasses 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 its progenitor was a massive star with strong mass loss. But, despite thelarge amount of observational data from optical, IR, radio, and x-ray observations, the identity of Cas A progenitor is still elusive.Aims. In this work, we computed stellar and circumstellar numerical models to look for the progenitor of Cas A. The models arecompared with the observational constraints that come from chemical observed abundances and dynamical information.Methods. We first computed stellar evolution models to get time-dependent wind parameters and surface abundances using the codeSTERN. To explore the range of masses proposed by several previous works, we chose a set of probable progenitor stars with initialmasses of 23, 28, 29, 30, and 33 M_⊙, with initial solar composition (Y = 0.28,Z 0.02) and mass loss. The derived loss ratesand wind terminal velocities are used as inner boundary conditions in the explicit, hydrodynamical code ZEUS-3D to simulate theevolution of the circumstellar medium. We simplified the calculations by using one-dimensional grids in the main sequence and redsuper-giant (RSG) stages, and two-dimensional grids for 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. Wenamed these type of stars "luminous blue super giant" (LBSGs) to distinguish them from normal blue super giants (BSGs) of muchlower initial masses. The 23 M_⊙star explodes as an RSG in a ρ~r~(-2)dense, free-streaming wind surrounded by thin, compressed,RSG shell. The 28 M_⊙star explodes as an LBSG, and the SN blast wave interacts with a low density, free streaming wind surroundedby an unstable and massive "RSG+LBSG" shell. Finally, the 30 and 33 M_⊙stars explode as WR surrounded by fast windsthat terminate in a highly fragmented "WR+RSG shell". We compared the surface chemical abundances of our stellar models withthe observational abundances in Cas A. The abundance analysis shows that the progenitor was a star with an initial mass of about30 M_⊙, while the hydrodynamical analysis favors progenitors with initial masses around 23.