The evolution of massive stars and their spectra I. A non-rotating 60 Msun star from the zero-age main sequence to the pre-supernova stage

摘要

For the first time, the interior and spectroscopic evolution of a massivestar is analyzed from the zero-age main sequence (ZAMS) to the pre-supernova(SN) stage. For this purpose, we combined stellar evolution models using theGeneva code and atmospheric models using CMFGEN. With our approach, we wereable to produce observables, such as a synthetic high-resolution spectrum andphotometry, aiding the comparison between evolution models and observed data.Here we analyze the evolution of a non-rotating 60 Msun star and its spectrumthroughout its lifetime. Interestingly, the star has a supergiant appearance(luminosity class I) even at the ZAMS. We find the following evolutionarysequence of spectral types: O3 I (at the ZAMS), O4 I (middle of the H-coreburning phase), B supergiant (BSG), B hypergiant (BHG), hot luminous bluevariable (LBV; end of H-core burning), cool LBV (H-shell burning through thebeginning of the He-core burning phase), rapid evolution through late WN andearly WN, early WC (middle of He-core burning), and WO (end of He-core burninguntil core collapse). We find the following spectroscopic phase lifetimes:3.22e6 yr for the O-type, 0.34e5 yr (BSG), 0.79e5 yr (BHG), 2.35e5 yr (LBV),1.05e5 yr (WN), 2.57e4 yr (WC), and 3.80e4 yr (WO). Compared to previousstudies, we find a much longer (shorter) duration for the early WN (late WN)phase, as well as a long-lived LBV phase. We show that LBVs arise naturally insingle-star evolution models at the end of the MS when the mass-loss rateincreases as a consequence of crossing the bistability limit. We discuss theevolution of the spectra, magnitudes, colors, and ionizing flux across thestar's lifetime, and the way they are related to the evolution of the interior.[abridged]