We present a study of the extreme O-type supergiant He 3–759 using new high-resolution FEROS data , revealing that it is a near spectroscopic twin of HD 151804 ( O8 Iaf ) .
We investigate the extinction towards He 3–759 using a variety of methods , revealing A _ { V } \sim 4.7 ^ { m } .
If we assume He 3–759 has an identical absolute K -band magnitude to HD 151804 we find that it lies in the Sagittarius-Carina spiral arm at a distance of \sim 6.5 kpc .
We derive the physical and wind properties for He 3–759 , revealing T _ { \ast } = 30.5 kK , \log L / L _ { \odot } = 5.9 and \dot { M } = 10 ^ { -5.17 } M _ { \odot } yr ^ { -1 } for a clumped wind whose terminal velocity is estimated at 1000 km s ^ { -1 } .
The atmosphere of He 3–759 is enriched in helium ( X _ { He } = 49 % ) and nitrogen ( X _ { N } = 0.3 % ) .
A reanalysis of HD 151804 and HD 152408 ( WN9ha ) reveals similar parameters except that the WN9ha star possesses a stronger wind and reduced surface hydrogen content .
HD 151804 and HD 152408 lie within the Sco OB1 association , with initial masses of \sim 60 M _ { \odot } and ages \sim 2.7 Myr , consistent with NGC 6231 cluster members using standard Geneva isochrones .
Improved agreement with observed surface abundances are obtained for similar initial masses with more recent Geneva group predictions from which higher ages of \sim 3.75 Myr are obtained .
No young , massive star cluster is known to be associated with He 3–759 .