BAT99-9 – a WC4 Wolf?Rayet star with nitrogen emission: evidence for binary evolution?

ABSTRACT An analysis of the Large Magellanic Cloud (LMC) WC4 star BAT99-9 (HD 32125, FD 4, Brey 7, WS 3) shows that still contains photospheric nitrogen. Three N emission features (N v ??1238, 1242, iv ?1719, and ??3479–3485) are unambiguously identified in spectrum. cmfgen models yield an N/C ratio 0.004 ± 0.002 (by number) a C/He $0.15_{-0.05}^{+0.10}$. Due to similarity other stars, good fit achieved by both classic spectrum lines, we argue lines intrinsic BAT99-9. examination limited set rotating for single-star evolution at LMC Galactic metallicities model with metallicity (z = 0.014) progenitor mass around 50 M? can have similar to, or larger than, what observe significant fraction its lifetime. However, 0.006) inconsistent observations. Both single binary BPASS predict many WC stars their While cover wider range luminosities provide somewhat better match BAT99-9, it is not currently possible rule out being formed through evolution, given uncertainties mass-loss rates, treatment convection mixing processes.