Advances in radiatively driven wind models

Puls, J.; Repolust, T.; Hoffmann, T. L.; Jokuthy, Alexander; Venero, R. O. J.

doi:10.1017/s0074180900211650

Cited by 22 publications

(9 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is in agreement with findings of Puls et al (2003), which showed that the inclusion of line blanketing at SMC metallicities resulted in a much more modest change in T eff relative to that found for Galactic stars.…”

Section: Metallicitysupporting

confidence: 92%

Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

Mokiem¹,

Martín-Hernández

Lenorzer³

et al. 2004

A&A

View full text Add to dashboard Cite

Abstract. We present a systematic study of the effect of metallicity on the stellar spectral energy distribution (SED) of O main sequence (dwarf) stars, focussing on the hydrogen and helium ionizing continua, and on the optical and near-IR lines used for spectral classification. The spectra are based on non-LTE line blanketed atmosphere models with stellar winds calculated using the  code of Hillier & Miller (1998). We draw the following conclusions. First, we find that the total number of Lyman photons emitted is almost independent of line blanketing effects and metallicity for a given effective temperature. This is because the flux that is blocked by the forest of metal lines at λ < 600 Å is redistributed mainly within the Lyman continuum.Second, the spectral type, as defined by the ratio of the equivalent widths of He  λ4471 and He  λ4542, is shown to depend noticeably on the microturbulent velocity in the atmosphere, on metallicity and, within the luminosity class of dwarfs, on gravity. Third, we confirm the decrease in T eff for a given spectral type due to the inclusion of line blanketing recently found by e.g. Martins et al. (2002). Finally, we find that the SED below ∼450 Å is highly dependent on metallicity. This is reflected in the complicates the use of these nebular ratios as diagnostic tools for the effective temperature determination of the ionizing stars in H  regions and for age dating of starburst regions in galaxies.

show abstract

Section: Metallicitysupporting

confidence: 92%

Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

Mokiem¹,

Martín-Hernández

Lenorzer³

et al. 2004

A&A

View full text Add to dashboard Cite

show abstract

“…In contrast, there is strong empirical evidence that stellar winds are in fact strongly clumped (e.g., Hamann & Koesterke 1998;Eversberg et al 1998;Puls et al 2003). This supports hydrodynamic models (Owocki et al 1988;Feldmeier 1995) which show that most of the material in a radiatively driven wind is compressed into a series of dense shells by the instability.…”

Section: Introductionsupporting

confidence: 54%

X-ray emission lines from inhomogeneous stellar winds

Oskinova¹,

Feldmeier²,

Hamann³

2004

A&A

127

View full text Add to dashboard Cite

Abstract. It is commonly adopted that X-rays from O stars are produced deep inside the stellar wind, and transported outwards through the bulk of the expanding matter which attenuates the radiation and affects the shape of emission line profiles. The ability of the X-ray observatories Chandra and XMM-Newton to resolve these lines spectroscopically provided a stringent test for the theory of the X-ray production. It turned out that none of the existing models was able to fit the observations consistently. The possible caveat of these models was the underlying assumption of a smooth stellar wind. Motivated by the evidence that the stellar winds are in fact structured, we present a 2-D numerical model of a stochastic, inhomogeneous wind. Small parcels of hot, X-ray emitting gas are permeated by cool, absorbing wind material which is compressed into thin shell fragments. Wind fragmentation alters the radiative transfer drastically, compared to homogeneous models of the same mass-loss rate. X-rays produced deep inside the wind, which would be totally absorbed in a homogeneous flow, can effectively escape from a fragmented wind. The wind absorption becomes wavelength independent if the individual fragments are optically thick. The X-ray line profiles are flat-topped in the blue part and decline steeply in the red part for the winds with a short acceleration zone. For the winds where the acceleration extends over significant distances, the lines can appear nearly symmetric and only slightly blueshifted, in contrast to the skewed, triangular line profiles typically obtained from homogeneous wind models of high optical depth. We show that profiles from a fragmented wind model can reproduce the observed line profiles from ζ Orionis. The present numerical modeling confirms the results from a previous study, where we derived analytical formulae from a statistical treatment.

show abstract

“…A comparison of the "observed" wind-momentum rates with theoretical predictions from Vink et al (2000) and independent calculations performed by our group (Puls et al 2003) 2 , revealed that objects with H α in emission and those with H α in absorption form two distinct WLRs. The latter is in agreement with theory, whilst the former appears to be located in parallel, but above the theoretical relation.…”

Section: Introductionmentioning

confidence: 81%

“…Notwithstanding its considerable successes (e.g., Vink et al 2000;Kudritzki 2002;Puls et al 2003), the theory is certainly over-simplified. Stellar rotation (e.g., Puls et al 1999 and references therein), and the intrinsic instability of the line-driving mechanism (see below), produce nonspherical and inhomogeneous structure, observationally evident from, e.g., X-ray emission and line-profile variability (for summaries, see Oskinova et al 2004 regarding the present status of X-ray line emission).…”

Section: Introductionmentioning

confidence: 99%

Bright OB stars in the Galaxy

Puls¹,

Маркова²,

Scuderi³

et al. 2006

A&A

291

391

View full text Add to dashboard Cite

Context. Recent results strongly challenge the canonical picture of massive star winds: various evidence indicates that currently accepted mass-loss rates,Ṁ, may need to be revised downwards, by factors extending to one magnitude or even more. This is because the most commonly used mass-loss diagnostics are affected by "clumping" (small-scale density inhomogeneities), influencing our interpretation of observed spectra and fluxes. Aims. Such downward revisions would have dramatic consequences for the evolution of, and feedback from, massive stars, and thus robust determinations of the clumping properties and mass-loss rates are urgently needed. We present a first attempt concerning this objective, by means of constraining the radial stratification of the so-called clumping factor. Methods. To this end, we have analyzed a sample of 19 Galactic O-type supergiants/giants, by combining our own and archival data for H α , IR, mm and radio fluxes, and using approximate methods, calibrated to more sophisticated models. Clumping has been included into our analysis in the "conventional" way, by assuming the inter-clump matter to be void. Because (almost) all our diagnostics depends on the square of density, we cannot derive absolute clumping factors, but only factors normalized to a certain minimum. Results. This minimum was usually found to be located in the outermost, radio-emitting region, i.e., the radio mass-loss rates are the lowest ones, compared toṀ derived from H α and the IR. The radio rates agree well with those predicted by theory, but are only upper limits, due to unknown clumping in the outer wind. H α turned out to be a useful tool to derive the clumping properties inside r < 3. . .5 R . Our most important result concerns a (physical) difference between denser and thinner winds: for denser winds, the innermost region is more strongly clumped than the outermost one (with a normalized clumping factor of 4.1 ± 1.4), whereas thinner winds have similar clumping properties in the inner and outer regions. Conclusions. Our findings are compared with theoretical predictions, and the implications are discussed in detail, by assuming different scenarios regarding the still unknown clumping properties of the outer wind.

show abstract

Advances in radiatively driven wind models

Cited by 22 publications

References 9 publications

Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

X-ray emission lines from inhomogeneous stellar winds

Bright OB stars in the Galaxy

Contact Info

Product

Resources

About