Photometric determination of surface gravities for G- and K-type giants of different metallicity

Tautvaisiene, G.; Lazauskaite, R.

doi:10.1515/astro-1993-0206

Cited by 4 publications

(19 citation statements)

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“…Our C/N ratio is in good agreement with the earlier estimates of [C/N]= −0.24 and −0.25 (adjusted to the Asplund et al (2009) scale) by Savanov & Berdyugina (1994) and Tautvaišienė et al (2010a), bearing in mind the "0.2-0.3 dex" uncertainty they assess for their C/N abundance ratio.…”

Section: Observations and Analysissupporting

confidence: 92%

“…Our observed C/N ratio for λ And is perfectly consistent with an unevolved composition, showing no signs of post dredge-up change. In contrast, Savanov & Berdyugina (1994) and Tautvaišienė et al (2010a) found an unambiguous signature of dredge-up in the carbon isotope ratio for which they derived 12 C/ 13 C= 20 ± 5 and 14, respectively. In the following we adopt the average of these values, 12 C/ 13 C= 17 ± 5, though our conclusions would be unchanged regardless of whether we adopted either result.…”

Section: Discussionmentioning

confidence: 91%

“…Denissenkov et al (2006) have also piqued interest in these stars through theoretical modelling that indicates extra mixing on the RGB might be induced by tidal spin-up. In this context, the nearby (26 pc) old disk giant λ And presents an interesting case: it is a mildly metal-poor first-ascent G8 III-IV star at an evolutionary phase in which CN-cycle products should have just appeared at its surface due to first dredge-up (Savanov & Berdyugina 1994;Donati et al 1995;Ottmann et al 1998;Tautvaišienė et al 2010a; further characteristics are listed in Table 1). Other than its close binarity, it is similar to members of the sample of mildly metal-poor ([Fe/H]∼ −0.5) disk giants that Cottrell & Sneden (1986) found to have unevolved (approximately solar) C/N ratios, but lower 12 C/ 13 C ratios of ∼ 10-30 than predicted by canonical models and reminiscent some of those seen in earlier studies of field giants toward solar metallicity (Lambert & Ries 1981;Kjaergaard et al 1982).…”

Section: Introductionmentioning

confidence: 99%

“…In §2 we use a precise X-ray measurement of the surface C/N abundance of λ And to show that it is typical of old disk giants from the Cottrell & Sneden (1986) sample. In §3, we combine this measurement with the 12 C/ 13 C assessments of Tautvaišienė et al (2010a) and Savanov & Berdyugina (1994) and compare the results with predictions from a state-of-theart stellar evolutionary model including thermohaline mixing.…”

Section: Introductionmentioning

confidence: 99%

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CLOSE TO THE DREDGE: PRECISE X-Ray C AND N ABUNDANCES IN Λ ANDROMEDA AND ITS PRECOCIOUS RED GIANT BRANCH MIXING PROBLEM

Drake

Ball

Eldridge

et al. 2011

The Astronomical Journal

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Chandra LETG+HRC-S and XMM-Newton RGS spectra of H-like C and N lines formed in the corona of the primary star of the RS CVn-type binary λ And, a mildly metal-poor G8 III-IV first ascent giant that completed dredgeup ∼ 50 Myr ago, have been used to make a precise measurement of its surface C/N ratio. We obtain the formal result [C/N]=0.03 ±0.07, which is typical of old disk giants and in agreement with standard dredge-up theory for stars 1M ⊙ . In contrast, these stars as a group, including λ And, have 12 C/ 13 C 20, which is much lower than standard model predictions. We show that the abundances of the old disk giants are consistent with models including thermohaline mixing that begins at the red giant branch luminosity function "bump". Instead, λ And indicates that the 12 C/ 13 C anomaly can be present immediately following dredgeup, contrary to current models of extra mixing on the red giant branch. In the context of other recent C and N abundance results for RS CVn-type binaries it seems likely that the anomaly is associated with either strong magnetic activity, fast rotation, or both, rather than close binarity itself.

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Section: Observations and Analysissupporting

confidence: 92%

Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

CLOSE TO THE DREDGE: PRECISE X-Ray C AND N ABUNDANCES IN Λ ANDROMEDA AND ITS PRECOCIOUS RED GIANT BRANCH MIXING PROBLEM

Drake

Ball

Eldridge

et al. 2011

The Astronomical Journal

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“…(3) Effective temperature and surface gravity calibrations of Tautvaišienė (1987) and Tautvaišienė & Lazauskaitė (1993) which apply to metal-deficient giants. The accuracy of estimations is ±85 K for T e and 0.3 dex for log g.…”

Section: Methods Of Photometric Classificationmentioning

confidence: 99%

Classification of Metal-Deficient Dwarfs in the Vilnius Photometric System

2003

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The N2K Consortium. V. Identifying Very Metal‐rich Stars with Low‐Resolution Spectra: Finding Planet‐Search Targets

Robinson¹,

Strader²,

Ammons³

et al. 2006

ApJ

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We present empirical calibrations that provide estimates of stellar metallicity, effective temperature and surface gravity as a function of Lick/IDS indices. These calibrations have been derived from a training set of 261 stars for which (1) high-precision measurements of [Fe/H], T eff and log g have been made using spectral-synthesis analysis of HIRES spectra, and (2) Lick indices have also been measured. Estimation of atmospheric parameters with low-resolution spectroscopy rather than photometry has the advantage of producing a highly accurate metallicity calibration, and requires only one observation per star. Our calibrations have identified a number of bright (V < 9) metal-rich stars which are now being screened for hot Jupiter-type planets. Using the Yonsei-Yale stellar models, we show that the calibrations provide distance estimates accurate to ∼ 20% for nearby stars. We have also investigated the possibility of constructing a "planeticity" calibration, to predict the presence of planets based on stellar abundance ratios, but find no evidence that a convincing relation of this type can be established. High metallicity remains the best single indicator that a given star is likely to harbor extrasolar planets.

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Photometric determination of surface gravities for G- and K-type giants of different metallicity

Cited by 4 publications

References 0 publications

CLOSE TO THE DREDGE: PRECISE X-Ray C AND N ABUNDANCES IN Λ ANDROMEDA AND ITS PRECOCIOUS RED GIANT BRANCH MIXING PROBLEM

CLOSE TO THE DREDGE: PRECISE X-Ray C AND N ABUNDANCES IN Λ ANDROMEDA AND ITS PRECOCIOUS RED GIANT BRANCH MIXING PROBLEM

Classification of Metal-Deficient Dwarfs in the Vilnius Photometric System

The N2K Consortium. V. Identifying Very Metal‐rich Stars with Low‐Resolution Spectra: Finding Planet‐Search Targets

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