The H<i>α</i>Balmer line as an effective temperature criterion

Cayrel, Roger; Veer-Menneret, C. van 't; Allard, N. F.; Stehlé, C.

doi:10.1051/0004-6361/201116911

Cited by 34 publications

(47 citation statements)

References 32 publications

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“…The Elodie Q T eff = 4 or spectroscopic scale (and hence our method, which uses it for calibration), seems to be in good agreement with the recent results of Cayrel et al (2011). These authors have calculated the effective temperature for 11 stars derived from angular diameters and bolometric fluxes, a technique which is expected to give the most fundamental measurement of the effective temperature.…”

Section: Temperature Scalessupporting

confidence: 86%

“…the B − V/b − y Casagrande et al (2010) IRFM-based calibrations, are compatible. We also compare with three additional sources of effective temperatures: the original scale of Alonso et al (1996) adopted by Allende Prieto et al (2004) in S 4 N, the spectroscopic temperatures derived by Katz et al (1998) from Elodie spectra, and the direct determinations by Cayrel et al (2011).…”

Section: Temperature Scalesmentioning

confidence: 99%

“…In this paper we introduce a new method of inferring the effective temperature of a star. Our procedure is inspired by the work by Cayrel et al (2011), who derive effective temperatures by modeling the Hα line, correcting for systematic errors by linearly mapping their temperatures to a scale based on angular diameters and absolute fluxes. We condense the information on T eff contained in stellar spectra using principal component analysis (PCA).…”

Section: Introductionmentioning

confidence: 99%

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A PCA approach to stellar effective temperatures

Bermejo

Ramos

Prieto

2013

A&A

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Context. The derivation of the effective temperature of a star is a critical first step in a detailed spectroscopic analysis. Spectroscopic methods suffer from systematic errors related to model simplifications. Photometric methods may be more robust, but are exposed to the distortions caused by interstellar reddening. Direct methods are difficult to apply, since fundamental data of high accuracy are hard to obtain. Aims. We explore a new approach in which the spectrum is used to characterize a star's effective temperature based on a calibration established by a small set of standard stars. Methods. We perform principal component analysis on homogeneous libraries of stellar spectra, then calibrate a relationship between the principal components and the effective temperature using a set of stars with reliable effective temperatures. Results. We find that our procedure gives excellent consistency when spectra from a homogenous set of observations are used. Systematic offsets may appear when combining observations from different sources. Using as reference the spectra of stars with high-quality spectroscopic temperatures in the Elodie library, we define a temperature scale for FG-type disk dwarfs with an internal consistency of about 50 K, in excellent agreement with temperatures from direct determinations and widely used scales based on the infrared flux method.

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Section: Temperature Scalessupporting

confidence: 86%

Section: Temperature Scalesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A PCA approach to stellar effective temperatures

Bermejo

Ramos

Prieto

2013

A&A

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“…The synthetic spectrum corresponding to our final model does not perfectly fit the hydrogen line profiles; this would require a slightly lower temperature by ∼50-100 K, which is ruled out by analysis of the metal lines (see below). The difference between our final synthetic and observed profiles can be attributed to normalisation, which is always challenging for hydrogen lines observed withéchelle spectra (Fossati et al 2011), and to three dimensional effects (Cayrel et al 2011), which are not taken into account in our 1D model.…”

Section: Global Parameters -T Eff Log G and [Fe/h]mentioning

confidence: 99%

Near-uniform internal rotation of the main-sequence γ Doradus pulsator KIC 7661054

Murphy

Fossati

Bedding

et al. 2016

Mon. Not. R. Astron. Soc.

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We used Kepler photometry to determine the internal rotation rate of KIC 7661054, a chemically normal γ Dor star on the main sequence at spectral type F2.5 V. The core rotation period of 27.25 ± 0.06 d is obtained from the rotational splittings of a series of dipole g modes. The surface rotation period is calculated from a spectroscopic projected rotation velocity and a stellar radius computed from models. Literature data, obtained without inclusion of macroturbulence as a line-broadening mechanism, imply that the surface rotates much more quickly than the core, while our detailed analysis suggests that the surface may rotate slightly more quickly than the core and that the rotation profile is uniform within the 1-σ uncertainties. We discuss the pitfalls associated with the determination of surface rotation rates of slow rotators from spectroscopy in the absence of asteroseismic constraints. A broad signal is observed at low frequency, which we show cannot be attributed to rotation, contrary to previous suggestions concerning the origin of such signals.

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“…Effective temperature of the program stars was determined by fitting wings of the observed Hα line profiles with the theoretical Hα profiles (Fuhrmann et al 1993;Barklem 2008;Cayrel et al 2011). Theoretical line profiles were computed in LTE with a modified version of the Kurucz's BALMER code 3 , which allowed the usage of different theories for the self-broadening and Stark broadening of the line profile (see Sbordone et al 2010).…”

Section: Effective Temperaturesmentioning

confidence: 99%

Abundances of lithium, oxygen, and sodium in the turn-off stars of Galactic globular cluster 47 Tucanae

Dobrovolskas

Kučinskas

Bonifacio

et al. 2014

A&A

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Context. The cluster 47 Tuc is among the most metal-rich Galactic globular clusters and its metallicity is similar to that of metal-poor disc stars and open clusters. Like other globular clusters, it displays variations in the abundances of elements lighter than Si, which is generally interpreted as evidence of the presence of multiple stellar populations. Aims. We aim to determine abundances of Li, O, and Na in a sample of of 110 turn-off (TO) stars, in order to study the evolution of light elements in this cluster and to put our results in perspective with observations of other globular and open clusters, as well as with field stars. Methods. We use medium resolution spectra obtained with the GIRAFFE spectrograph at the ESO 8.2 m Kueyen VLT telescope and use state of the art 1D model atmospheres and NLTE line transfer to determine the abundances. We also employ CO 5 BOLD hydrodynamical simulations to assess the impact of stellar granulation on the line formation and inferred abundances. Results. Our results confirm the existence of Na-O abundance anti-correlation and hint towards a possible Li-O anti-correlation in the TO stars of 47 Tuc. At the same time, we find no convincing evidence supporting the existence of Li-Na correlation. The obtained 3D NLTE mean lithium abundance in a sample of 94 TO stars where Li lines were detected reliably, A(Li) 3D NLTE = 1.78 ± 0.18 dex, appears to be significantly lower than what is observed in other globular clusters. At the same time, star-to-star spread in Li abundance is also larger than seen in other clusters. The highest Li abundance observed in 47 Tuc is about 0.1 dex lower than the lowest Li abundance observed among the un-depleted stars of the metal-poor open cluster NGC 2243. Conclusions. The correlations/anti-correlations among light element abundances confirm that chemical enrichment history of 47 Tuc was similar to that of other globular clusters, despite the higher metallicity of 47 Tuc. The lithium abundances in 47 Tuc, when put into context with observations in other clusters and field stars, suggest that stars that are more metal-rich than [Fe/H] ∼ −1.0 experience significant lithium depletion during their lifetime on the main sequence, while the more metal-poor stars do not. Rather strikingly, our results suggest that initial lithium abundance with which the star was created may only depend on its age (the younger the star, the higher its Li content) and not on its metallicity.

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The HαBalmer line as an effective temperature criterion

Cited by 34 publications

References 32 publications

A PCA approach to stellar effective temperatures

A PCA approach to stellar effective temperatures

Near-uniform internal rotation of the main-sequence γ Doradus pulsator KIC 7661054

Abundances of lithium, oxygen, and sodium in the turn-off stars of Galactic globular cluster 47 Tucanae

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