Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-03-17
Astron.Astrophys. 420 (2004) 1087-1106
Astronomy and Astrophysics
Astrophysics
23 pages, 22 figures, A&A accepted
Scientific paper
10.1051/0004-6361:20034509
We present a quantitative study of the stellar and wind properties of massive stars in the compact star forming region SMC-N81. Non-LTE spherically extended atmosphere models including line-blanketing have been computed with the code CMFGEN (Hillier & Miller 1998) and the analysis of UV STIS spectra lead to the following results: 1) The SMC-N81 components are young (~ 0-4 Myrs) O stars with Teff compatible with medium to late subtypes and with luminosities lower than average Galactic O dwarfs, rendering them possible ZAMS candidates; 2) The winds are extremely weak: the mass loss rates (~1e-8/1e-9 Msol/yr) and the modified wind momenta are 1 to 2 orders of magnitude lower than observed so far for Galactic stars, and are lower than the predictions of the most recent hydrodynamical models. The reasons for such weak winds are investigated with special emphasis on the modified wind momenta: 1) There may be a break-down of the wind momentum - luminosity relation (WLR) for dwarf stars at low luminosity (log L/Lsol < 5.5). However, reasons for such a breakdown remain unknown; 2) The slope of the WLR may be steeper at low metallicity. This is predicted by the radiation driven wind theory, but the current hydrodynamical simulations do not show any change of the slope at SMC metallicity. Moreover, there are indications that some Galactic objects have wind momenta similar to those of the SMC stars; 3) Decoupling in the atmosphere may lead to multicomponent winds, but various tests indicate that this is not likely to be the case for the SMC-N81 stars. Hence, the origin of the weakness of the wind observed in these objects remains unknown. We suggest that this weakness may be linked with the youth of these stars and represents possibly the onset of stellar winds in recently formed massive stars.
Heydari-Malayeri Mohammad
Hillier Desmond John
Martins Fabrice
Schaerer Daniel
No associations
LandOfFree
Puzzling wind properties of young massive stars in SMC-N81 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Puzzling wind properties of young massive stars in SMC-N81, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Puzzling wind properties of young massive stars in SMC-N81 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-151627