WO2 Wolf-Rayet Stars
The "surface" visible is actually the wind
photosphere — the inner point where the stellar wind becomes optically thick.
The true stellar surface lies hidden beneath.
β-law wind: v(r) = v∞(1−R★/r)β
— smaller β = faster acceleration near surface.
Emission shells:
- r≈1.8: HeII 4686Å ionization (cyan-blue)
- r≈3.2: OVI+OIII emission nebula (teal-green)
WR-102 is one of the hottest known stars.
Its extreme UV/X-ray luminosity dominates; visible light is the
Rayleigh-Jeans tail of a ~210 kK blackbody.