Macroclumping as solution of the discrepancy between Ha and P v mass loss diagnostics for O-type stars

被引：89

作者：

Surlan, B. ^{[1
,2
]}

Hamann, W. -R. ^{[3
]}

Aret, A. ^{[4
]}

Kubat, J. ^{[1
]}

Oskinova, L. M. ^{[3
]}

Torres, A. F. ^{[5
,6
]}

机构：

[1] Akad Ved Ceske Republ, Astron Ustav, Ondrejov 25165, Czech Republic

[2] Matemat Inst SANU, Belgrade 11001, Serbia

[3] Univ Potsdam, Inst Phys & Astron, D-14476 Potsdam, Germany

[4] Tartu Observ, EE-61602 Toravere, Tartumaa, Estonia

[5] Univ Nacl La Plata, Fac Ciencias Astron & Geofis, Dept Espect, La Plata, Buenos Aires, Argentina

[6] Univ Nacl La Plata, CONICET, CCT La Plata, Inst Astrofis La Plata, La Plata, Buenos Aires, Argentina

来源：

ASTRONOMY & ASTROPHYSICS | 2013年 / 559卷

关键词：

stars:; winds; outflows; stars: mass-loss; stars: early-type; DRIVEN STELLAR WINDS; RESONANCE LINE FORMATION; NLTE-MODELS; LOSS RATES; RADIATIVE-TRANSFER; MAGELLANIC-CLOUD; BINARY STARS; ZETA PUPPIS; HOT; SPECTROSCOPY;

D O I：

10.1051/0004-6361/201322390

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Context. Recent studies of O-type stars have demonstrated that discrepant mass-loss rates are obtained when different diagnostic methods are employed. Fitting the unsaturated UV resonance lines (e.g., P v) gives drastically lower values than obtained from the Ha emission. Wind inhomogeneity (so-called "clumping") may be the main cause of this discrepancy. Aims. In a previous paper, we presented 3D Monte-Carlo calculations for the formation of scattering lines in a clumped stellar wind. In the present paper we select five O-type supergiants (from 04 to 07) and test whether the reported discrepancies can be resolved this way. Methods. In the first step, the analyses started with simulating the observed spectra with Potsdam Wolf-Rayet (PoWR) non-LTE model atmospheres. The mass-loss rates are adjusted to fit to the observed Ha emission lines best. For the unsaturated UV resonance lines (i.e., P v) we then applied our 3D Monte-Carlo code, which can account for wind clumps of any optical depths ("macroclumping"), a non-void interclump medium, and a velocity dispersion inside the clumps. The ionization stratifications and underlying photospheric spectra were adopted from the PoWR models. The properties of the wind clumps were constrained by fitting the observed resonance line profiles. Results. Our results show that with the mass-loss rates that fit Ha (and other Balmer and He II lines), the UV resonance lines (especially the unsaturated doublet of P v) can also be reproduced with no problem when macroclumping is taken into account. There is no need to artificially reduce the mass-loss rates or to assume a subsolar phosphorus abundance or an extremely high clumping factor, unlike what was claimed by other authors. These consistent mass-loss rates are lower by a factor of 1.3 to 2.6, compared to the mass-loss rate recipe from Vink et al. Conclusions. Macroclumping resolves the previously reported discrepancy between Ha and P v mass-loss diagnostics.

引用

页数：17