FUNDAMENTAL PARAMETERS OF WOLF-RAYET STARS .4. WEAK-LINED WNE STARS

A detailed study of 3 'weak-lined' Galactic WN3-4 stars (WR46=HD 10499 4, WR128=HD 187282 and WR152=HD 211564) has been carried out based on new ultraviolet, optical and infrared spectroscopy. Tailored analyses, using the WR standard model, allow determinations of stellar paramete rs and chemical abundances based on the observed hydrogen, helium, car bon, nitrogen and oxygen spectrum,leading to higher stellar temperatur es and luminosities than previously thought. We find that the temperat ures (50-90kK) and luminosities (log L/L.=4.8-5.5) of our weak-lined W NE sample lie close to the strong-lined WNE's, but with mass-loss rate s over an order of magnitude lower (log M/M. yr(-1)similar to-5.2) lea ding to smaller atmospheric extensions. Fairly low luminosities (10(5) L.) are found for WR128 and WR152 although hydrogen is clearly presen t (around 10% by mass). Such WR stars are not currently predicted by s ingle star evolutionary theory, while close binary evolution may provi de a possible explanation. For these objects, metal abundances are con sistent with CNO-equilibrium values (N/He similar or equal to 0.004, C /N similar or equal to 0.05, C/O similar or equal to 1), while an unus ual oxygen abundance is found for WR46 (N/He similar or equal to 0.006 , O/N similar or equal to 0.1, C/O<0.3). Our results support the Popul ation I WR nature of WR46 (with a possible compact companion) rather t han a low mass X-ray binary, as has been suggested.