Studies on the spectra of K-giants - I. Physical parameters and Fe and Ti abundances for 26 K-giants

Gratton, L.; Gaudenzi, S.; Rossi, C.; Gratton, R. G.

doi:10.1093/mnras/201.3.807

Cited by 20 publications

(15 citation statements)

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“…c This is star [BHM2000] 139 of Bonifacio et al (2000). (1) This paper, (2) Lambert & Ries (1981), (3) Gratton et al (1982), (4) Komarov & Shcherbak (1980), (5) Komarov et al (1985), (6) Gratton & Ortolani (1986), (7) (2002) is quite similar to ours except for the 3 truly metal-poor stars, out of their sample of 14; analogs to these are totally lacking in our sample. It is relevant to point out that Monaco et al (2002), exactly Quite correctly Cole, pointed out that this estimate could in fact be too low, since the relations are calibrated on GGCs and age effects may bias downwards the results by 0.1−0.2 dex; furthermore the lack of α-enhancement in Sgr (confirmed by the present analysis), at variance with GCCs, would also act in the direction to lower the photometric metallicity estimate.…”

Section: Metallicity Distributionsupporting

confidence: 67%

The Sgr dSph hosts a metal-rich population

Bonifacio

Sbordone

Marconi

et al. 2004

A&A

114

163

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Abstract.We report on abundances of O, Mg, Si, Ca and Fe for 10 giants in the Sgr dwarf spheroidal derived from high resolution spectra obtained with UVES at the 8.2 m Kueyen-VLT telescope. The iron abundance spans the range −0.8 < ∼ [Fe/H] < ∼ 0.0 and the dominant population is relatively metal-rich with [Fe/H] ∼ −0.25. The α/Fe ratios are slightly subsolar, even at the lowest observed metallicities suggesting a slow or bursting star formation rate. From our sample of 12 giants (including the two observed by Bonifacio et al. 2000) we conclude that a substantial metal rich population exists in Sgr, which dominates the sample. The spectroscopic metallicities allow one to break the age-metallicity degeneracy in the interpretation of the colour-magnitude diagram (CMD). Comparison of isochrones of appropriate metallicity with the observed CMD suggests an age of 1 Gyr or younger, for the dominant Sgr population sampled by us. We argue that the observations support a star formation that is triggered by the passage of Sgr through the Galactic disc, both in Sgr and in the disc. This scenario has also the virtue of explaining the mysterious "bulge C stars" as disc stars formed in this event. The interaction of Sgr with the Milky Way is likely to have played a major role in its evolution.

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Section: Metallicity Distributionsupporting

confidence: 67%

The Sgr dSph hosts a metal-rich population

Bonifacio

Sbordone

Marconi

et al. 2004

A&A

114

163

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“…One of the possible reasons may be that the infrared regions used in this work are not overly occupied by lines. The effective temperatures obtained are in good agreement with that indicated by Gratton et al (1982). Conversely, gravities are close to that derived by McWilliam (1990) and Lambert & Ries (1981 Drake & Smith (1991) showed for β Gem, that metallicities are not significantly affected by departures from NLTE.…”

Section: Discussionsupporting

confidence: 89%

Atmosphere parameters of four K-giants obtained by spectrum fitting

Krtička

Štefl

1999

Astron. Astrophys. Suppl. Ser.

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Abstract. Basic parameters of the atmospheres (i.e., T eff , log g, [A/H], v turb ) of four late type giant stars α Ari, α Boo, α Cas, β Gem are obtained by matching synthetic spectra to observed ones. We used model atmosphere to compute the synthetic spectrum. The parameters of the model atmosphere and of the synthetic spectrum are fitted to match the observed spectrum, accelerated by means of a proposed numerical tool.

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“…Only Gratton et al (1982) and Gratton (1983) have tabulated a value of log g = 2.1, a result which was obtained from a curve of growth technique. Also the gravity value given by Burnashev (1983) -who has used narrow-band photometric colours in the visible part of the electromagnetic spectrum -is quite discrepant from the more common listed value of log g = 2.9.…”

Section: Comparison With Other Published Stellarmentioning

confidence: 99%

ISO-SWS calibration and the accurate modelling of cool-star atmospheres

Decin

Vandenbussche

Waelkens

et al. 2003

A&A

127

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Abstract.A detailed spectroscopic study of 11 giants with spectral type from G9 to M2 is presented. The 2.38-4.08 µm wavelength-range of band 1 of ISO-SWS (Short-Wavelength Spectrometers on board of the Infrared Space Observatory) in which many different molecules -with their own dependence on each of the stellar parameters -are absorbing, enables us to estimate the effective temperature, the gravity, the microturbulence, the metallicity, the CNO-abundances, the 12 C/ 13 C-ratio and the angular diameter from the ISO-SWS data. Using the Hipparcos' parallax, the radius, luminosity and gravity-inferred mass are derived. The stellar parameters obtained are in good agreement with other published values, though also some discrepancies with values deduced by other authors are noted. For a few stars (δ Dra, ξ Dra, α Tuc, H Sco and α Cet) some parameters -e.g. the CNO-abundances -are derived for the first time. By examining the correspondence between different ISO-SWS observations of the same object and between the ISO-SWS data and the corresponding synthetic spectrum, it is shown that the relative accuracy of ISO-SWS in band 1 (2.38-4.08 µm) is better than 2% for these high-flux sources. The high level of correspondence between observations and theoretical predictions, together with a confrontation of the estimated T eff (ISO) value with T eff values derived from colours -which demonstrates the consistency between V − K, BC K , T eff and θ d derived from optical or IR data -proves that both the used  models to derive the stellar quantities and the flux calibration of the ISO-SWS detectors have reached a high level of reliability.

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Studies on the spectra of K-giants - I. Physical parameters and Fe and Ti abundances for 26 K-giants

Cited by 20 publications

References 0 publications

The Sgr dSph hosts a metal-rich population

The Sgr dSph hosts a metal-rich population

Atmosphere parameters of four K-giants obtained by spectrum fitting

ISO-SWS calibration and the accurate modelling of cool-star atmospheres

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