Constraints on the Ionization Balance of Hot‐Star Winds from<i>FUSE</i>Observations of O Stars in the Large Magellanic Cloud

Massa, Derck; Fullerton, A. W.; Sonneborn, G.; Hutchings, J. B.

doi:10.1086/367786

Cited by 106 publications

(155 citation statements)

References 65 publications

(86 reference statements)

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“…6 the predicted ionization fractions in comparison with those derived from observation as a function of effective stellar temperature. Note that here we use the ionization fractions derived for LMC stars (Massa et al 2003), because their observational sample includes a large number of ionization stages, the fractions of which are given as a function of velocity, and the wind parameters of LMC stars are not significantly different from Galactic ones. Since several parameters except the effective temperature (e.g., the wind density) may influence the ionization fractions, the graphs in Fig.…”

Section: Ionization Fractionsmentioning

confidence: 99%

X-ray emission from hydrodynamical simulations in non-LTE wind models

Krtička

Feldmeier

Oskinova

et al. 2009

A&A

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Hot stars are sources of X-ray emission originating in their winds. Although hydrodynamical simulations that are able to predict this X-ray emission are available, the inclusion of X-rays in stationary wind models is usually based on simplifying approximations. To improve this, we use results from time-dependent hydrodynamical simulations of the line-driven wind instability (seeded by the base perturbation) to derive the analytical approximation of X-ray emission in the stellar wind. We use this approximation in our non-LTE wind models and find that an improved inclusion of X-rays leads to a better agreement between model ionization fractions and those derived from observations. Furthermore, the slope of the L X − L relation is in better agreement with observations, however the X-ray luminosity is underestimated by a factor of three. We propose a possible solution for this discrepancy.

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Section: Ionization Fractionsmentioning

confidence: 99%

X-ray emission from hydrodynamical simulations in non-LTE wind models

Krtička

Feldmeier

Oskinova

et al. 2009

A&A

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“…The observed mass-loss rates may be influenced by wind clumping (e.g. Crowther et al 2002;Massa et al 2003;Bouret et al 2003) and thus, the observed mass-loss rates shall be lower in such a case (see also Kramer et al 2003, for the discussion of effect of clumping on the theoretical profiles of X-ray lines). However, in such a case clumping would influence also the theoretical mass-loss rates (cf.…”

Section: Mass Loss Ratesmentioning

confidence: 99%

NLTE models of line-driven stellar winds

Krtička

Kubát

2004

A&A

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Abstract. New numerical models of line-driven stellar winds of late O stars are presented. Statistical equilibrium (NLTE) equations of the most abundant elements are solved. Properly obtained occupation numbers are used to calculate consistent radiative force and radiative heating terms. Wind density, velocity and temperature are calculated as a solution of model hydrodynamical equations. Contrary to other published models we account for a multicomponent wind nature and do not simplify the calculation of the radiative force (e.g. using force multipliers). We discuss the convergence behaviour of our models. The ability of our models to predict correct values of mass-loss rates and terminal velocities of selected late O stars (mainly giants and supergiants) is demonstrated. The systematic difference between predicted and observed terminal velocities reported in the literature has been removed. Moreover, we found good agreement between the theoretical wind momentum-luminosity relationship and the observed one for Cyg OB2 supergiants.

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“…Fullerton: Very similar discrepancies are seen in samples of O-type stars observed with FUSE in both the LMC (Crowther et al 2002, Massa et al 2003 and SMC (Hillier et al 2003). Although these samples are limited, they don't provide any evidence to suggest that the degree of clumping depends strongly on the overall metallicity of the star.…”

Section: Discussionmentioning

confidence: 89%

“…5 shows that measurements ofṀ from ρ 2 diagnostics for a "blue-ribbon" sample of 40 Galactic O-type stars are always greater than measurements from the P v resonance lines by a factor of at least 20 (Fullerton, Massa, & Prinja 2006). Detailed model atmosphere calculations indicate similar levels of disagreement between Hα and the P v doublet for O-type supergiants in the Galaxy (Bouret et al 2005), Large Magellanic Cloud (Crowther et al 2002;Massa et al 2003) and Small Magellanic Cloud (Hillier et al 2003).…”

Section: Discrepant Mass-loss Estimatesmentioning

confidence: 88%

Structure in the winds of O-Type stars: observations and inferences

Fullerton

2010

Proc. IAU

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Abstract. This review describes the observational evidence for structure in the winds of Otype stars due to large-scale perturbations and small-scale inhomogeneities. Despite considerable progress, a comprehensive theoretical framework that explains the origin. properties, and coexistence of wind structure on different spatial scales has yet to be constructed and incorporated into model atmosphere analyses. Consequently, it is not yet possible to assess the effect of non-stationary structures on different wind diagnostics in a rigorous way, with the result that accurate empirical determinations of mass-loss rates remain elusive.

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Constraints on the Ionization Balance of Hot‐Star Winds fromFUSEObservations of O Stars in the Large Magellanic Cloud

Abstract: We present Far Ultraviolet Spectroscopic Explorer (FUSE) spectra for 25 O stars in the Large Magellanic Cloud (LMC). We analyze wind profiles for the

Cited by 106 publications

References 65 publications

X-ray emission from hydrodynamical simulations in non-LTE wind models

X-ray emission from hydrodynamical simulations in non-LTE wind models

NLTE models of line-driven stellar winds

Structure in the winds of O-Type stars: observations and inferences

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