Spectral analyses of galactic Wolf Rayet stars

A comprehensive study of Galactic WR stars using spectral analyses with lineblanketed PoWR models (Hamann et al. (2006) for WN stars; Barniske et al. (2006) for WC stars) revealed a bimodal WR-subtype distribution in the HRD, where the H-rich WNL stars are located to the right of the ZAMS with luminosities above 106 L0, whereas the (mostly H-free) early to intermediate WN subtypes, as well as the WC stars, have lower luminosities and hotter temperatures (see Figure 33.1).

This dichotomy already implies that the H-rich WNL stars are the descendants of very-massive stars, possibly still in the phase of central H-burning, whereas the earlier subtypes (including the WC stars) are more-evolved, less-massive, He-burning objects. Note, however, that distance estimates are available for only a small part of the WNL sample. Some of these objects thus might have lower luminosities and be the direct progenitors of the earlier subtypes.

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