A Tale of Two Stars: The Extreme O7 Iaf+ Supergiant AV 83 and the OC7.5 III((f)) star AV 69

Hillier, D. J.; Lanz, T.; Heap, Sara R.; Hubený, I.; Smith, L. J.; Evans, C. J.; Lennon, D. J.; Bouret, Jean-Claude

doi:10.1086/374329

Cited by 183 publications

(387 citation statements)

References 56 publications

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“…Many of these stars have been analysed to derive mass-loss rates confirming the expected theoretical trend of mass-loss with metallicity ( [1], [5], [10], [11], [4]) while theoretical expectations for terminal velocities have also been confirmed [3]. However, a small number of stars were found to have mass-loss rates which are an order of magnitude or more less than theoretical predictions [1], see Fig.3.…”

Section: Weak Winds In the Small Magellanic Cloudsupporting

confidence: 54%

UV Spectroscopy of Metal-Poor Massive Stars in the Small Magellanic Cloud

Lennon

2009

The Impact of HST on European Astronomy

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Summary. The Hubble Space Telescope has provided the first clear evidence for weaker winds of metal-poor massive stars in the Small Magellanic Cloud, confirming theoretical predictions of the metallicity dependence of mass-loss rates and wind terminal velocities. For lower luminosity O-type stars however, derived mass-loss rates are orders of magnitude lower than predicted, and are at present unexplained.

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Section: Weak Winds In the Small Magellanic Cloudsupporting

confidence: 54%

UV Spectroscopy of Metal-Poor Massive Stars in the Small Magellanic Cloud

Lennon

2009

The Impact of HST on European Astronomy

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“…Estimates of effective temperatures (in kK) for different spectral types for the current sample (TAR), for supergiants in the LMC (Trundle et al 2007, LMC), a sample of Galactic supergiants (Fraser et al 2010, GAL) and for class Ia supergiants (Crowther et al 2006, CLW here, analysed the spectra of over 50 Galactic supergiants with luminosity classes ranging from Ia + to II. Crowther et al (2006) analysed the spectra of 25 class Ia supergiants using the model atmosphere code  (Hillier et al 2003). Additionally they considered some other analyses when providing their estimates.…”

Section: Atmospheric Parameters For the Single And Binary Samplesmentioning

confidence: 99%

The VLT-FLAMES Tarantula Survey

McEvoy

Dufton

Evans

et al. 2015

A&A

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Context. Model atmosphere analyses have been previously undertaken for both Galactic and extragalactic B-type supergiants. By contrast, little attention has been given to a comparison of the properties of single supergiants and those that are members of multiple systems. Aims. Atmospheric parameters and nitrogen abundances have been estimated for all the B-type supergiants identified in the VLT-FLAMES Tarantula survey. These include both single targets and binary candidates. The results have been analysed to investigate the role of binarity in the evolutionary history of supergiants.Methods.  non-local thermodynamic equilibrium (LTE) model atmosphere calculations have been used to determine atmospheric parameters and nitrogen abundances for 34 single and 18 binary supergiants. Effective temperatures were deduced using the silicon balance technique, complemented by the helium ionisation in the hotter spectra. Surface gravities were estimated using Balmer line profiles and microturbulent velocities deduced using the silicon spectrum. Nitrogen abundances or upper limits were estimated from the N  spectrum. The effects of a flux contribution from an unseen secondary were considered for the binary sample. Results. We present the first systematic study of the incidence of binarity for a sample of B-type supergiants across the theoretical terminal age main sequence (TAMS). To account for the distribution of effective temperatures of the B-type supergiants it may be necessary to extend the TAMS to lower temperatures. This is also consistent with the derived distribution of mass discrepancies, projected rotational velocities and nitrogen abundances, provided that stars cooler than this temperature are post-red supergiant objects. For all the supergiants in the Tarantula and in a previous FLAMES survey, the majority have small projected rotational velocities. The distribution peaks at about 50 km s −1 with 65% in the range 30 km s −1 ≤ v e sin i ≤ 60 km s −1 . About ten per cent have larger v e sin i (≥100 km s −1 ), but surprisingly these show little or no nitrogen enhancement. All the cooler supergiants have low projected rotational velocities of ≤70 km s −1 and high nitrogen abundance estimates, implying that either bi-stability braking or evolution on a blue loop may be important. Additionally, there is a lack of cooler binaries, possibly reflecting the small sample sizes. Single-star evolutionary models, which include rotation, can account for all of the nitrogen enhancement in both the single and binary samples. The detailed distribution of nitrogen abundances in the single and binary samples may be different, possibly reflecting differences in their evolutionary history. Conclusions. The first comparative study of single and binary B-type supergiants has revealed that the main sequence may be significantly wider than previously assumed, extending to T eff = 20 000 K. Some marginal differences in single and binary atmospheric parameters and abundances have been identified, possibly implying non-stand...

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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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A Tale of Two Stars: The Extreme O7 Iaf+ Supergiant AV 83 and the OC7.5 III((f)) star AV 69

Cited by 183 publications

References 56 publications

UV Spectroscopy of Metal-Poor Massive Stars in the Small Magellanic Cloud

UV Spectroscopy of Metal-Poor Massive Stars in the Small Magellanic Cloud

The VLT-FLAMES Tarantula Survey

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

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