Atmospheric NLTE-models for the spectroscopic analysis of blue stars with winds

Puls, J.; Urbaneja, M. A.; Venero, R. O. J.; Repolust, T.; Springmann, U.; Jokuthy, Alexander; Mokiem, M.R.

doi:10.1051/0004-6361:20042365

Cited by 447 publications

(550 citation statements)

References 46 publications

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“…We derived the stellar atmospheric parameters using a grid of synthetic stellar atmosphere models built using the atmosphere/line formation code fastwind (Santolaya-Rey et al 1997;Puls et al 2005;Rivero González et al 2012). The code takes into account non-local thermo-dynamical equilibrium effects in spherical symmetry with an explicit treatment of the stellar wind.…”

Section: Observations Data Reduction and Resultsmentioning

confidence: 99%

Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2

Pillitteri¹,

Fossati²,

Castro³

et al. 2018

A&A

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Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them (∼ 10%) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V star ρ Oph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyzed FORS2 ESO VLT spectra of ρ Oph A taken at two epochs and detected a longitudinal component of the magnetic field of order of ∼ 500 G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters of ρ Oph A and further constrained its age. We conclude that ρ Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars.

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Section: Observations Data Reduction and Resultsmentioning

confidence: 99%

Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2

Pillitteri¹,

Fossati²,

Castro³

et al. 2018

A&A

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“…Additionally, a normal helium to hydrogen ratio of 0.1 by number of atoms was assumed. The validity of such an approach was investigated by Dufton et al (2005), who analysed the spectra of B-type Ia supergiants in the SMC using the current grid and also theoretical spectra generated by the  code (Santolaya-Rey et al 1997;Puls et al 2005), that incorporates wind effects. Dufton et al (2005) found excellent agreement in the atmospheric parameters estimated from the two methods.…”

Section: Methodsmentioning

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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“…While detailed information about the latest version used here can be found in Puls et al (2005), we highlight only those points which are important for our analysis of B stars.…”

Section: Determination Of Stellar and Wind Parametersmentioning

confidence: 99%

Bright OB stars in the Galaxy

Маркова¹,

Puls²

2007

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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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Atmospheric NLTE-models for the spectroscopic analysis of blue stars with winds

Cited by 447 publications

References 46 publications

Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2

Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2

The VLT-FLAMES Tarantula Survey

Bright OB stars in the Galaxy

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