Spectral characteristics of fast rotating metal-poor massive stars

TL;DR

This study predicts the spectral features of fast-rotating, very metal-poor massive stars using advanced stellar models, aiding future observational comparisons and understanding their role in cosmic phenomena.

Contribution

It combines stellar evolution and atmosphere models to generate synthetic spectra for metal-poor, fast-rotating massive stars across different evolutionary stages.

Findings

Early phases resemble early-O type giants or supergiants.

Later phases predominantly show WO-type spectral characteristics.

Predicted spectra will be compared with HST observations for validation.

Abstract

Low-metallicity massive stars are assumed to be progenitors of certain supernovae, gamma-ray bursts, and gravitational wave emitting mergers. These exotic phenomena contribute to their host galaxies through strong ionizing radiation and mechanical feedback. Here we investigate a certain type of very metal-poor (0.02 Zsun) hot massive single stars that rotate fast and evolve chemically homogeneously. Combining state-of-the-art theories of stellar evolution and stellar atmospheres modelling we predict synthetic spectra of these stars corresponding to different masses and evolutionary phases. The predicted spectra in early evolutionary phases is classified mainly as an early-O type giant or supergiant while in later evolutionary phases most of our model spectra are assigned to the WO-type spectral class. The Hubble Space Telescope's (HST) Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) program will enable us to compare our predicted spectra with observations of stars of similar nature (e.g., metal-poor stars in Sextant A).