H-alpha observations of early-type stars

Scuderi, S.; Bonanno, G.; Benedetto, Rosario Di; Spadaro, D.; Panagia, N.

doi:10.1086/171418

Cited by 21 publications

(19 citation statements)

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“…The Hα profiles of the sample stars derived throughout our observations are quite similar, both in shape and strength, to those obtained by other investigators in various epochs (e.g., Rosendhal 1973;Conti & Frost 1977;Scuderi et al 1992;Ebbets 1982;Underhill 1995;Kaper et al 1997). This finding suggests that the atmospheres of our targets are not subject to long-term variability.…”

Section: Summary Discussion and Conclusionsupporting

confidence: 86%

Bright OB stars in the Galaxy

Маркова¹,

Puls²,

Scuderi³

et al. 2005

A&A

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Abstract.We investigate the line-profile variability (lpv) of Hα for a large sample of O-type supergiants (15 objects between O4 and O9.7), in an objective, statistically rigorous manner. We employed the Temporal Variance Spectrum (TVS) analysis, developed for the case of photospheric absorption lines and modified by us to take into account the effects of wind emission. By means of a comparative analysis we place constraints on the properties of this variability -quantified in terms of a mean and a newly defined fractional amplitude of deviations -as a function of stellar and wind parameters. The results of our analysis show that all the stars in the sample show evidence of significant lpv in Hα, mostly dominated by processes in the wind. The variations occur between zero and 0.3 v ∞ (i.e., below ∼1.5 R ), in good agreement with results from similar studies. A comparison between the observations and corresponding line-profile simulations indicates that for stars with intermediate wind densities the properties of the Hα variability can be explained by simple models consisting of coherent or broken shells (blobs) uniformly distributed over the wind volume, with an intrinsic scatter in the maximum density contrast of about a factor of two. For stars at lower and higher wind densities, on the other hand, we found certain inconsistencies between the observations and our predictions, most importantly concerning the mean amplitude and the symmetry properties of the TVS. This disagreement might be explained by the presence of coherent large-scale structures, partly confined in a volume close to the star. Interpreted in terms of a variable mass-loss rate, the observed variations of Hα indicate changes of ±4% with respect to the mean value ofṀ for stars with stronger winds and of ± 16% for stars with weaker winds. The effect of these variations on the corresponding wind momenta is rather insignificant (less than 0.16 dex), increasing only the local scatter without affecting the Wind Momentum Luminosity Relationship.

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Section: Summary Discussion and Conclusionsupporting

confidence: 86%

Bright OB stars in the Galaxy

Маркова¹,

Puls²,

Scuderi³

et al. 2005

A&A

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“…In the case of completely clumped winds and owing to the suggested radial stratification of the clumping factor (Owocki et al 2000), radio and Hα mass-loss rates might differ significantly. The comparisons performed so far do not give evidence of any systematic difference (Lamers & Leitherer 1993;Scuderi & Panagia 2000). Note, however, that in view of the interpretation by Puls et al (2003) also this result needs to be re-investigated (cf.…”

Section: Introductionmentioning

confidence: 89%

Bright OB stars in the Galaxy

Маркова

Puls

Repolust

et al. 2003

A&A

118

201

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Abstract. We study mass-loss and wind momentum rates of 29 Galactic O-type stars with luminosity classes I, III and V by means of a pure Hα profile analysis and investigate to what extent the results compare to those originating from a state-ofthe-art, complete spectral analysis. Our investigation relies on the approximate method developed by Puls et al. (1996) which we have modified to account for the effects of line-blanketing. Effective temperatures and gravities needed to obtain quantitative results from such a simplified approach have been derived by means of calibrations based on most recent spectroscopic NLTE analyses and models of Galactic stars by Repolust et al. (2003) and Martins et al. (2002). Comparing (i) the derived winddensities to those determined by Repolust et al. (2003) for eleven stars in common and (ii) the Wind-momentum Luminosity Relationship (WLR) for our sample stars to those derived by other investigations, we conclude that our approximate approach is actually able to provide consistent results. Additionally, we studied the consequences of "fine tuning" some of the direct and indirect parameters entering the WLR, especially by accounting for different possible values of stellar reddening and distances. Combining our data set with the corresponding data provided by Herrero et al. (2002) and Repolust et al. (2003) we finally study the WLR for the largest sample of Galactic O-type stars gathered so far, including an elaborate error treatment. The established disagreement between the theoretical predictions and the "observed" WLRs being a function of luminosity class is suggested to be a result of wind clumping. Different strategies to check this hypothesis are discussed, particularly by comparing the Hα mass-loss rates with the ones derived from radio observations.

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“…5 where we compare calculated and observed mass-loss rates. We compiled observed mass-loss rates based on the Hα measurement (Leitherer 1988;Scuderi et al 1992;Puls et al 1996;Crowther & Bohannan 1997;Scuderi et al 1998;Lamers et al 1999) and on the radio emission (Lamers & Leitherer 1993;Scuderi et al 1998) together with mass-loss determinations obtained using UV lines by BG. Generally, UV line-diagnostic is believed to be badly affected by the unknown wind ionization fractions .…”

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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H-alpha observations of early-type stars

Cited by 21 publications

References 0 publications

Bright OB stars in the Galaxy

Bright OB stars in the Galaxy

Bright OB stars in the Galaxy

NLTE models of line-driven stellar winds

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