Spectral models for binary products: Unifying Subdwarfs and Wolf-Rayet stars as a sequence of stripped-envelope stars

Understand

Stars stripped of their envelope through interaction in a binary are generally not considered when accounting for ionizing radiation from stellar populations, despite the expectation that stripped stars emit hard ionizing radiation, form frequently and live 10-100 times longer than single massive stars.

• We compute the first grid of spectral models specially made for stars stripped in binaries for a range of progenitor masses (2-20$M_{\odot}$) and metallicities covering a wide range.
• For stripped stars with masses between 0.3-7$M_{\odot}$, we find high effective temperatures (20-100 kK, increasing with mass), small radii (0.2-1$R_{\odot}$) and high bolometric luminosities, comparable to that of their progenitor before stripping.
• The spectra show a continuous sequence that naturally bridges subdwarf-type stars and Wolf-Rayet like spectra.