On the effective temperatures and surface gravities of superficially 
normal main sequence band B and A stars

Adelman, Saul J.; Pintado, O. I.; Nieva, F.; Rayle, K. E.; Sanders, S. E.

doi:10.1051/0004-6361:20020889

Cited by 36 publications

(32 citation statements)

References 23 publications

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“…We took advantage of previous studies of early B-type stars (Grigsby et al 1992;Gies & Lambert 1992;Kilian 1992;Cunha & Lambert 1994;Andrievsky et al 1999;Adelman et al 2002;Lyubimkov et al 2004;Morel et al 2006) to compile our target list. Criteria were the stars to be i) bright: early B-type stars near the main sequence of magnitude V < 6 mag are located at distances <500 pc, with such a brightness limit facilitating high-quality spectra to be obtained with relative ease; ii) sharp lined: low (projected) rotational velocities v sin i < ∼ 40 km s −1 allow spectral line analyses to be done at highest precision, maximising the chances to identify line blends and to place the continuum unambiguously;…”

Section: Primary Target Selectionmentioning

confidence: 99%

Present-day cosmic abundances

Nieva

Przybilla²

2012

A&A

450

506

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Context. Early B-type stars are ideal indicators for present-day cosmic abundances since they preserve their pristine abundances and typically do not migrate far beyond their birth environments over their short lifetimes, in contrast to older stars like the Sun. They are also unaffected by depletion onto dust grains, unlike the cold/warm interstellar medium (ISM) or H ii regions. Aims. A carefully selected sample of early B-type stars in OB associations and the field within the solar neighbourhood is studied comprehensively. Quantitative spectroscopy is used to characterise their atmospheric properties in a self-consistent way. Present-day abundances for the astrophysically most interesting chemical elements are derived in order to investigate whether a present-day cosmic abundance standard can be established. Methods. High-resolution and high-S/N FOCES, FEROS and ELODIE spectra of well-studied sharp-lined early B-type stars are analysed in non-LTE. Line-profile fits based on extensive model grids and an iterative analysis methodology are used to constrain stellar parameters and elemental abundances at high accuracy and precision. Atmospheric parameters are derived from the simultaneous establishment of independent indicators, from multiple ionization equilibria and the Stark-broadened hydrogen Balmer lines, and they are confirmed by reproduction of the stars' global spectral energy distributions. Results. Effective temperatures are constrained to 1-2% and surface gravities to less than 15% uncertainty, along with accurate rotational, micro-and macroturbulence velocities. Good agreement of the resulting spectroscopic parallaxes with those from the new reduction of the Hipparcos catalogue is obtained. Absolute values for abundances of He, C, N, O, Ne, Mg, Si and Fe are determined to better than 25% uncertainty. The synthetic spectra match the observations reliably over almost the entire visual spectral range. Three sample stars, γ Ori, o Per and θ 1 Ori D, are identified as double-lined, indicating the presence of an early/mid B-type companion. Conclusions. A present-day cosmic abundance standard is established from a sample of 29 early B-type stars, indicating abundance fluctuations of less than 10% around the mean. Our results (i) resolve the long-standing discrepancy between a chemical homogeneous gas-phase ISM and a chemically inhomogeneous young stellar component out to several hundred parsec from the Sun, (ii) facilitate the amount of heavy elements locked up in the interstellar dust to be constrained precisely -the results imply that carbonaceous dust is largely destroyed inside the Orion H ii region, unlike the silicates, and that graphite is only a minority species in interstellar dust -, (iii) show that the mixing of CNO-burning products in the course of massive star evolution follows tightly the predicted nuclear path, (iv) provide reliable present-day reference points for anchoring Galactic chemical evolution models to observation, and (v) imply that the Sun has migrated outwards from the inne...

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Section: Primary Target Selectionmentioning

confidence: 99%

Present-day cosmic abundances

Nieva

Przybilla²

2012

A&A

450

506

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“…We have chosen: (1) de Jager & Nieuwenhuijzen (1987) because it was used by Cranmer (2005) to discuss the distribution of rotational velocities of Be stars; (2) the calibration of the ubvy−Strömgren photometric indices given by Moon & Dworetsky (1985) and revisited by Napiwotzki et al (1993); and (3) the effective temperatures derived from fitted visible spectral energy distributions by Adelman et al (2002), Fitzpatrick & Massa (2005), and Nieva (2013). In …”

Section: Appendix A: Fundamental Parametersmentioning

confidence: 99%

Critical study of the distribution of rotational velocities of Be stars

Zorec

Frémat

Souza

et al. 2016

A&A

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Context. Among intermediate-mass and massive stars, Be stars are the fastest rotators in the main sequence (MS) and, as such, these stars are a cornerstone to validate models of structure and evolution of rotating stars. Several phenomena, however, induce under-or overestimations either of their apparent Vsin i, or true velocity V. Aims. In the present contribution we aim at obtaining distributions of true rotational velocities corrected for systematic effects induced by the rapid rotation itself, macroturbulent velocities, and binarity. Methods. We study a set of 233 Be stars by assuming they have inclination angles distributed at random. We critically discuss the methods of Cranmer and Lucy-Richardson, which enable us to transform a distribution of projected velocities into another distribution of true rotational velocities, where the gravitational darkening effect on the Vsin i parameter is considered in different ways. We conclude that iterative algorithm by Lucy-Richardson responds at best to the purposes of the present work, but it requires a thorough determination of the stellar fundamental parameters. Results. We conclude that once the mode of ratios of the true velocities of Be stars attains the value V/V c 0.77 in the main-sequence (MS) evolutionary phase, it remains unchanged up to the end of the MS lifespan. The statistical corrections found on the distribution of ratios V/V c for overestimations of Vsin i, due to macroturbulent motions and binarity, produce a shift of this distribution toward lower values of V/V c when Be stars in all MS evolutionary stages are considered together. The mode of the final distribution obtained is at V/V c 0.65. This distribution has a nearly symmetric distribution and shows that the Be phenomenon is characterized by a wide range of true velocity ratios 0.3 V/V c 0.95. It thus suggests that the probability that Be stars are critical rotators is extremely low. Conclusions. The corrections attempted in the present work represent an initial step to infer indications about the nature of the Be-star surface rotation that will be studied in the second paper of this series.

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“…4) The temperature is evaluated by comparing the observed visual or UV fluxes with predictions from line-blanketed LTE model atmospheres, as in Malagnini et al (1983); Morossi & Malagnini (1985); Malagnini & Morossi (1990). 5) The temperature is computed by means of: a) NLTE lineblanketed model analysis of ionization balances due to He i/ ii, Si iii/ iv and Si ii/ iii on moderate resolution spectra, as done by McErlean et al (1999) using the code TLUSTY (Hubeny 1988); or b) LTE line-blanketed model fitting of the optical region and Hγ profile using ATLAS9 model atmospheres as in Adelman et al (2002). 6) The temperature is determined from synthetic fits to the optical spectral range of B supergiants employing unified NLTE line-and non-LTE BW extended model atmosphere codes, such as FASTWIND or CMFGEN (Hillier et al 2003), as in Searle et al (2008); Markova & Puls (2008);Crowther et al (2006).…”

Section: Effective Temperaturesmentioning

confidence: 99%

Fundamental parameters of B supergiants from the BCD system

Zorec¹,

Cidale

Arias

et al. 2009

A&A

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Context. Effective temperatures of early-type supergiants are important to test stellar atmosphere-and internal structure-models of massive and intermediate mass objects at different evolutionary phases. However, these T eff values are more or less discrepant depending on the method used to determine them. Aims. We aim to obtain a new calibration of the T eff parameter for early-type supergiants as a function of observational quantities that are: a) highly sensitive to the ionization balance in the photosphere and its gas pressure; b) independent of the interstellar extinction; c) as much as possible model-independent. Methods. The observational quantities that best address our aims are the (λ 1 , D) parameters of the BCD spectrophotometric system. They describe the energy distribution around the Balmer discontinuity, which is highly sensitive to T eff and log g. We perform a calibration of the (λ 1 , D) parameters into T eff using effective temperatures derived with the bolometric-flux method for 217 program stars, whose individual uncertainties are on average |ΔT eff |/T f eff = 0.05. Results. We obtain a new and homogeneous calibration of the BCD (λ 1 , D) parameters for OB supergiants and revisit the current calibration of the (λ 1 , D) zone occupied by dwarfs and giants. The final comparison of calculated with obtained T eff values in the (λ 1 , D) calibration show that the latter have total uncertainties, which on average are T eff /T f eff ±0.05 for all spectral types and luminosity classes. Conclusions. The effective temperatures of OB supergiants derived in this work agree on average within some 2000 K with other determinations found in the literature, except those issued from wind-free non-LTE plane-parallel models of stellar atmospheres, which produce effective temperatures that can be overestimated by up to more than 5000 K near T eff = 25 000 K. Since the stellar spectra needed to obtain the (λ 1 , D) parameters are of low resolution, a calibration based on the BCD system is useful to study stars and stellar systems like open clusters, associations or stars in galaxies observed with multi-object spectrographs and/or spectro-imaging devices.

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On the effective temperatures and surface gravities of superficially normal main sequence band B and A stars

Cited by 36 publications

References 23 publications

Present-day cosmic abundances

Present-day cosmic abundances

Critical study of the distribution of rotational velocities of Be stars

Fundamental parameters of B supergiants from the BCD system

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