The VLT-FLAMES survey of massive stars: Nitrogen abundances for Be-type stars in the Magellanic Clouds

Dunstall, P. R.; Brott, I.; Dufton, P. L.; Lennon, D. J.; Evans, Christopher J.; Smartt, S. J.; Hunter, I.

doi:10.1051/0004-6361/201117588

Cited by 39 publications

(44 citation statements)

References 43 publications

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“…We expect the near-critically rotating OB stars in our Case B systems to be Be stars. Given that Be stars are often not or only weakly enriched in nitrogen (Lennon et al 2005, Dunstall et al 2011, in contrast to predictions from rotating single star models, the population of Be stars may be dominated by binaryinteraction products.…”

Section: Ob Star Rotation and Surface Abundancesmentioning

confidence: 99%

Properties of OB star−black hole systems derived from detailed binary evolution models

Langer

Schürmann

Stoll

et al. 2020

A&A

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Context. The recent gravitational wave measurements have demonstrated the existence of stellar mass black hole binaries. It is essential for our understanding of massive star evolution to identify the contribution of binary evolution to the formation of double black holes. Aims. A promising way to progress is investigating the progenitors of double black hole systems and comparing predictions with local massive star samples such as the population in 30 Doradus in the Large Magellanic Cloud (LMC). Methods. To this purpose, we analyse a large grid of detailed binary evolution models at LMC metallicity with initial primary masses between 10 and 40 M , and identify which model systems potentially evolve into a binary consisting of a black hole and a massive main sequence star. We then derive the observable properties of such systems, as well as peculiarities of the OB star component. Results. We find that ∼3% of the LMC late O and early B stars in binaries are expected to possess a black hole companion, when assuming stars with a final helium core mass above 6.6 M to form black holes. While the vast majority of them may be X-ray quiet, our models suggest that these may be identified in spectroscopic binaries, either by large amplitude radial velocity variations ( ∼ > 50 km s −1 ) and simultaneous nitrogen surface enrichment, or through a moderate radial velocity ( ∼ > 10 km s −1 ) and simultaneously rapid rotation of the OB star. The predicted mass ratios are such that main sequence companions could be excluded in most cases. A comparison to the observed OB+WR binaries in the LMC, Be/X-ray binaries, and known massive BH binaries supports our conclusion. Conclusions. We expect spectroscopic observations to be able to test key assumptions in our models, with important implications for massive star evolution in general, and for the formation of double-black hole mergers in particular.

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Section: Ob Star Rotation and Surface Abundancesmentioning

confidence: 99%

Properties of OB star−black hole systems derived from detailed binary evolution models

Langer

Schürmann

Stoll

et al. 2020

A&A

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“…The equivalent widths and hydrogen profiles of these stars were rescaled to allow for an unseen secondary in a similar manner to that used to correct for Be-type disc contamination in Dunstall et al (2011). Both the original atmospheric parameters and those implied by a 20% secondary contribution are summarised in Table 5.…”

Section: Contribution Of Secondary Starsmentioning

confidence: 99%

“…Quantitative analysis of these objects was presented in a series of articles by Dufton et al (2006), Trundle et al (2007), Hunter et al (2007Hunter et al ( , 2008aHunter et al ( ,b, 2009a, and Dunstall et al (2011).…”

Section: Introductionmentioning

confidence: 99%

The VLT-FLAMES Tarantula Survey

McEvoy

Dufton

Evans

et al. 2015

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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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“…It is therefore gratifying to see crucial progress being made on this front, Rivero et al (2011) presenting a comprehensive analysis of the N iii line formation problem. Hunter et al (2009) also found that among their fast rotators there exists a wide range of nitrogen abundances, a result which was reflected in related work by Dunstall et al (2011) for Be stars. The lack of a strong correlation between rotational velocity and nitrogen enhancements in massive stars, together with almost bimodal distribution of rotational velocities, has led to speculation that binaries may play a more important role than was previously thought in the evolution of massive star populations (de Mink et al 2009a, even to the extent of perhaps explaining abundance anomalies in globular clusters (de Mink et al 2009b).…”

Section: Cno Anomalies In Massive Stars (D Lennon)mentioning

confidence: 60%

Commission 35: Stellar Constitution

Charbonnel¹,

Limongi²,

D’Antona³

et al. 2011

Proc. IAU

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Commission 35 consists of members of the International Astronomical Union whose research is concerned with the structure and evolution of stars in all parts of the H-R diagram. Their interests range from various aspects of stellar interior physics, such as convection, diffusion, rotation, magnetic fields, to asteroseismology and the prediction of the evolutionary and nucleosynthetic histories of stars that are of vital importance for our understanding of stellar populations and galactic chemical evolution.

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The VLT-FLAMES survey of massive stars: Nitrogen abundances for Be-type stars in the Magellanic Clouds

Cited by 39 publications

References 43 publications

Properties of OB star−black hole systems derived from detailed binary evolution models

Properties of OB star−black hole systems derived from detailed binary evolution models

The VLT-FLAMES Tarantula Survey

Commission 35: Stellar Constitution

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