Understanding B-type supergiants in the low metallicity environment of
 the SMC II

Trundle, C.; Lennon, D. J.

doi:10.1051/0004-6361:20042061

Cited by 93 publications

(140 citation statements)

References 38 publications

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“…This is similar to results found by other authors (e.g. Herrero et al 2002;Trundle et al 2004;Trundle & Lennon 2005;Searle et al 2008) from studies of supergiants in the Galaxy and SMC, using non-rotating (Schaller et al 1992), and rotating (Maeder & Meynet 2001) evolutionary models.…”

Section: Hertzsprung-russell Diagramsupporting

confidence: 92%

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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Section: Hertzsprung-russell Diagramsupporting

confidence: 92%

The VLT-FLAMES Tarantula Survey

McEvoy

Dufton

Evans

et al. 2015

A&A

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“…Compared to the evolutionary masses from Meynet & Maeder (2000) and apart from two cases, our estimates are generally lower, by approximately 0.05 to 0.38 dex, with larger differences for less luminous stars. While for some stars the discrepancies are less than or comparable to the corresponding errors (e.g., HD 185859, HD 190603 first entry, HD206165), they are significant for some others (mainly at lower luminosities) and might indicate a "mass discrepancy", in common with previous findings (Crowther et al 2006;Trundle & Lennon 2005). 10 A mass of 7 M as derived for HD 198478 (second entry) seems to be rather low for a SG, suggesting that the B-V colour adopted from SIMBAD is probably underestimated.…”

Section: Stellar Radii Luminosities and Massessupporting

confidence: 79%

“…This result might be interpreted as an indication of small or even negligible metallicity effects (both directly, via line-blanketing, and indirectly, via weaker winds) in the temperature regime of B-SGs, at least for metallicities in between solar and SMC (about 0.2 solar) values. Such an interpretation would somewhat contradict our findings about the strong influence of line-blanketing in the Galactic case (given that these effects should be lower in the SMC), but might be misleading since Trundle et al (2004Trundle et al ( , 2005 have used the spectral classification from Lennon (1997), which already accounts for the lower metallicity in the SMC. To check the influence of this reclassification, we recovered the original (MK) spectral types of the SMC targets using data provided by Lennon (1997 , Table 2), and subsequently compared them to our results for Galactic B-SGs.…”

Section: Comparison Of the Temperature Scales Of Galactic And Smc B Scontrasting

confidence: 63%

“…4. To our surprise, a comparison with data from similar SMC objects Trundle & Lennon 2005) did not reveal any systematic difference between the two temperature scales. This result is interpreted as an indication that the re-classification scheme as developed by Lennon (1997) to account for lower metal line strengths in SMC B-SGs also removes the effects of different degrees of line blanketing.…”

Section: Summary and Future Workcontrasting

confidence: 48%

“…where "SP" (0-9) gives the spectral type (from B0 to B9), and the standard deviation is ±1040 K. This regression was then compared to T eff estimates obtained by Trundle et al (2004) and Trundle & Lennon (2005) for B-SGs in the SMC. We decided to compare with these two studies only, because Trundle et al have used a similar (2004Trundle et al have used a similar ( ) or identical (2005 version of FASTWIND as we did here, i.e., systematic, model dependent differences between different datasets can be excluded and because the metallicity of the SMC is significantly lower than in the Galaxy, so that metallicity dependent effects should be maximised.…”

Section: Comparison Of the Temperature Scales Of Galactic And Smc B Smentioning

confidence: 99%

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Bright OB stars in the Galaxy

Маркова¹,

Puls²

2007

A&A

189

264

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Context. B-type supergiants represent an important phase in the evolution of massive stars. Reliable estimates of their stellar and wind parameters, however, are scarce, especially at mid and late spectral subtypes. Aims. We apply the NLTE atmosphere code FASTWIND to perform a spectroscopic study of a small sample of Galactic B-supergiants from B0 to B9. By means of the resulting data and incorporating additional datasets from alternative studies, we investigate the properties of OB-supergiants and compare our findings with theoretical predictions. Methods. Stellar and wind parameters of our sample stars are determined by line profile fitting, based on synthetic profiles, a Fourier technique to investigate the individual contributions of stellar rotation and "macro-turbulence" and an adequate approach to determine the Si abundances in parallel with micro-turbulent velocities. Results. Due to the combined effects of line-and wind-blanketing, the temperature scale of Galactic B-supergiants needs to be revised downward, by 10 to 20%, the latter value being appropriate for stronger winds. Compared to theoretical predictions, the wind properties of OB-supergiants indicate a number of discrepancies. In fair accordance with recent results, our sample indicates a gradual decrease in v ∞ over the bi-stability region, where the limits of this region are located at lower T eff than those predicted. Introducing a distance-independent quantity Q related to wind-strength, we show that this quantity is a well defined, monotonically increasing function of T eff outside this region. Inside and from hot to cool,Ṁ changes by a factor (in between 0.4 and 2.5) which is much smaller than the predicted factor of 5. Conclusions. The decrease in v ∞ over the bi-stability region is not over-compensated by an increase ofṀ , as frequently argued, provided that wind-clumping properties on both sides of this region do not differ substantially.

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Eta Carinae and the Luminous Blue Variables

Vink¹

2012

Eta Carinae and the Supernova Impostors

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We evaluate the place of Eta Carinae amongst the class of luminous blue variables (LBVs) and show that the LBV phenomenon is not restricted to extremely luminous objects like Eta Car, but extends luminosities as low as log(L/Lsun) = 5.4 - corresponding to initial masses ~25 Msun, and final masses as low as ~10-15 Msun. We present a census of S Doradus variability, and discuss basic LBV properties, their mass-loss behaviour, and whether at maximum light they form pseudo-photospheres. We argue that those objects that exhibit giant Eta Car-type eruptions are most likely related to the more common type of S Doradus variability. Alternative atmospheric models as well as sub-photospheric models for the instability are presented, but the true nature of the LBV phenomenon remains as yet elusive. We end with a discussion on the evolutionary status of LBVs - highlighting recent indications that some LBVs may be in a direct pre-supernova state, in contradiction to the standard paradigm for massive star evolution.Comment: 27 pages, 6 figures, Review Chapter in "Eta Carinae and the supernova imposters" (eds R. Humphreys and K. Davidson) new version submitted to Springe

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Understanding B-type supergiants in the low metallicity environment of the SMC II

Cited by 93 publications

References 38 publications

The VLT-FLAMES Tarantula Survey

The VLT-FLAMES Tarantula Survey

Bright OB stars in the Galaxy

Eta Carinae and the Luminous Blue Variables

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