Surface abundances of light elements for a large sample of early B-type stars - II. Basic parameters of 107 stars

Lyubimkov, L. S.; Rachkovskaya, T. M.; Rostopchin, S.; Lambert, David L.

doi:10.1046/j.1365-8711.2002.05341.x

Cited by 50 publications

(50 citation statements)

References 32 publications

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“…Useful temperature scales for early-type stars have been presented by Napiwotzki et al (1993), Daflon et al (1999) and Lyubimkov et al (2002), where the temperature can be estimated from reddening-independent photometric quantities (assuming a valid standard reddening-law). The first work scales the temperature to the [u − b] 2 -parameter from the narrow-band Strömgren ubvy-system.…”

Section: Temperature and Gravity Scalesmentioning

confidence: 99%

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Temperature, gravity, and bolometric correction scales for non-supergiant OB stars

Nieva

2013

A&A

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Context. Precise and accurate determinations of the atmospheric parameters effective temperature and surface gravity are mandatory to derive reliable chemical abundances in OB stars. Furthermore, fundamental parameters like distances, masses, radii, luminosities can also be derived from the temperature and gravity of the stars. Aims. Atmospheric parameters recently determined at high precision with several independent spectroscopic indicators in non-local thermodynamic equilibrium, with typical uncertainties of ∼300 K for temperature and of ∼0.05 dex for gravity, are employed to calibrate photometric relationships. This is in order to investigate whether a faster tool to estimate atmospheric parameters can be provided. Methods. Temperatures and gravities of 30 calibrators, i.e. well-studied OB main sequence to giant stars in the solar neighbourhood, are compared to reddening-independent quantities of the Johnson and Strömgren photometric systems, assuming normal reddening. In addition, we examine the spectral and luminosity classification of the star sample and compute bolometric corrections. Results. Calibrations of temperatures and gravities are proposed for various photometric indices and spectral types. Once the luminosity of the stars is well known, effective temperatures can be determined at a precision of ∼400 K for luminosity classes III/IV and ∼800 K for luminosity class V. Furthermore, surface gravities can reach internal uncertainties as low as ∼0.08 dex when using our calibration to the Johnson Q-parameter. Similar precision is achieved for gravities derived from the β-index and the precision is lower for both atmospheric parameters when using the Strömgren indices [c1] and [u − b]. In contrast, external uncertainties are larger for the Johnson than for the Strömgren calibrations. Our uncertainties are smaller than typical differences among other methods in the literature, reaching values up to ±2000 K for temperature and ±0.25 dex for gravity, and in extreme cases, +6000 K and ±0.4 dex, respectively. A parameter calibration for sub-spectral types is also proposed. Moreover, we present a new bolometric correction relation to temperature based on our empirical data, rather than on synthetic grids. Conclusions. The photometric calibrations presented here are useful tools to estimate effective temperatures and surface gravities of non-supergiant OB stars in a fast manner. This is also applicable to some single-line spectroscopic binaries, but caution has to be taken for undetected double-lined spectroscopic binaries and single objects with anomalous reddening-law, dubious photometric quantities and/or luminosity classes, for which the systematic uncertainties may increase significantly. We recommend to use these calibrations only as a first step of the parameter estimation, with subsequent refinements based on spectroscopy. A larger sample covering more uniformly the parameter space under consideration will allow refinements to the present calibrations.

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Section: Temperature and Gravity Scalesmentioning

confidence: 99%

“…Lyubimkov et al (2002) proposed, in addition, temperature scales for two significantly different values of gravity.…”

Section: Temperature and Gravity Scalesmentioning

confidence: 99%

Temperature, gravity, and bolometric correction scales for non-supergiant OB stars

Nieva

2013

A&A

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“…The best candidate stars are located in clusters or associations, where distances (and therefore luminosities) and ages can be constrained from photometry and main-sequence fitting. Despite the importance of this basic data in the astrophysical context, little work on masses, radii, luminosities and ages of early B-type stars has been published over the past two decades (Wolff 1990;Gies & Lambert 1992;Kilian 1992;Lyubimkov et al 2002;Hohle et al 2010, but all far less accurate and precise than the DEB data). Moreover, the astrophysical reference literature like the Landolt-Börnstein (Schmidt-Kaler 1982), which has also been adopted in more recent compilations like Allen's Astrophysical Quantities (Cox 2000), are based on the state-ofthe art achieved more than three decades ago.…”

Section: Introductionmentioning

confidence: 99%

Fundamental properties of nearby single early B-type stars

Nieva

Przybilla

2014

A&A

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Aims. Fundamental parameters of a sample of 26 apparently slowly-rotating single early B-type stars in OB associations and in the field within a distance of 400 pc from the Sun are presented and compared to high-precision data from detached eclipsing binaries (DEBs). Together with surface abundances for light elements the data are used to discuss the evolutionary status of the stars in context of the most recent Geneva grid of models for core hydrogen-burning stars in the mass-range ∼6 to 18 M at metallicity Z = 0.014. Methods. The fundamental parameters are derived on the basis of accurate and precise atmospheric parameters determined earlier by us from non-LTE analyses of high-quality spectra of the sample stars, utilising the new Geneva stellar evolution models. Results. Evolutionary masses plus radii and luminosities are determined to better than typically 5%, 10%, and 20% uncertainty, respectively, facilitating the mass−radius and mass−luminosity relationships to be recovered for single core hydrogen-burning objects with a similar precision as derived from DEBs. Good agreement between evolutionary and spectroscopic masses is found. Absolute visual and bolometric magnitudes are derived to typically ∼0.15−0.20 mag uncertainty. Metallicities are constrained to better than 15−20% uncertainty and tight constraints on evolutionary ages of the stars are provided. Overall, the spectroscopic distances and ages of individual sample stars agree with independently derived values for the host OB associations. Signatures of mixing with CN-cycled material are found in 1/3 of the sample stars. Typically, these are consistent with the amount predicted by the new Geneva models with rotation. The presence of magnetic fields appears to augment the mixing efficiency. In addition, a few objects are possibly the product of binary evolution. In particular, the unusual characteristics of τ Sco point to a blue straggler nature, due to a binary merger. Conclusions. The accuracy and precision achieved in the determination of fundamental stellar parameters from the quantitative spectroscopy of single early B-type stars comes close (within a factor 2-4) to data derived from DEBs. While our fundamental parameters are in good agreement with those derived from DEBs as a function of spectral type, significant systematic differences with data from the astrophysical reference literature are found. Masses are ∼10−20% and radii ∼25% lower then the recommended values for luminosity class V, resulting in the stars being systematically fainter than assumed usually, by ∼0.5 mag in absolute visual and bolometric magnitude. Our sample of giants is too small to derive firm conclusions, but similar trends as for the dwarfs are indicated.

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“…The effective temperatures T eff and other parameters for these stars were determined in Ref. 36, with T eff and log g found by the traditional method (using photometry and Balmer lines). All these stars are in the MS and lie within a neighborhood of the sun with a radius of 800 pc.…”

Section: Discussionmentioning

confidence: 99%

Possible Overionization of C II, N II, and O II Ions in the Atmospheres of Early B- and Late O-Type Stars

Lyubimkov

2013

Astrophysics

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The reliability of C, N, and O abundances determined from lines of C II, N II, and O II in the mainsequence (MS) early B-and late O-type stars is examined. This analysis is based on a fact of K for N II and O II) yield the undistorted C, N and O abundances, and their average values agree very well with modern estimates for the sun. This confirms that the metallicity of B-and O-type MS stars in the Sun's vicinity is the same as that of the sun. An explanation is given for the slight deficit of carbon found for the early B-type MS stars in previous work. It is noted that when an alternative method based on examining the ionization balance (e.g., He I-II, C II-III, Ne I-II, Si III-IV) is used to determine the parameters T eff and log g, the overionization problem essentially vanishes; however, this method leads to a systematic enhancement in the values of T eff and log g. The overionization problem can be solved by shifting to an Astrophysics, Vol. 56, No. 4, December, 2013

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Surface abundances of light elements for a large sample of early B-type stars - II. Basic parameters of 107 stars

Cited by 50 publications

References 32 publications

Temperature, gravity, and bolometric correction scales for non-supergiant OB stars

Temperature, gravity, and bolometric correction scales for non-supergiant OB stars

Fundamental properties of nearby single early B-type stars

Possible Overionization of C II, N II, and O II Ions in the Atmospheres of Early B- and Late O-Type Stars

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