A FEROS spectroscopic study of the extreme O supergiant He 3-759
Abstract
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 AV ∼ 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 6.5 kpc. We derive the physical and wind properties for He 3-759, revealing Tast = 30.5 kK, log L/L⊙ = 5.9 and dot{M} = 10-5.17 M⊙ 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 (XN = 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 60 M⊙ and ages 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 3.75 Myr are obtained. No young, massive star cluster is known to be associated with He 3-759.
Based on observations made with ESO telescopes at the La Silla observatory under program ID 082-D.0136.- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2009
- DOI:
- 10.1051/0004-6361/200912631
- arXiv:
- arXiv:0907.2539
- Bibcode:
- 2009A&A...503..985C
- Keywords:
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- stars: early-type;
- stars: fundamental parameters;
- stars:;
- individual: He 3-759;
- HD 151804;
- HD 152408;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 6 pages, 4 figures, accepted for A&