Spectroscopic Determination of Stellar Parameters and Oxygen Abundances for Hyades/Field G–K Dwarfs

Takeda, Yoichi; Honda, Satoshi

doi:10.3847/1538-3881/ab799f

Cited by 12 publications

(18 citation statements)

References 40 publications

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“…Aleo et al (2017) argue that the large differences between Fe I and Fe I may be related to blending of Fe II lines that become more severe at decreasing T eff . These results were corroborated by Takeda & Honda (2020), who also concluded that the O I overabundance obtained from the oxygen triplet by Schuler et al (2006) might be due to the different T eff scale and to over-estimation of the strength of the lines in coolest stars. Even though we are aware of the issues related to the spectroscopic analysis of young and cool stars and we are starting to shed light on the topic, we still lack a definitive solution.…”

Section: Introductionsupporting

confidence: 53%

The GAPS Programme at TNG

Baratella

D’Orazi

Biazzo

et al. 2020

A&A

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Context. The detailed chemical composition of stars is important in many astrophysical fields, among which is the characterisation of exoplanetary systems. Previous studies seem to indicate an anomalous chemical pattern of the youngest stellar population in the solar vicinity that has sub-solar metal content. This can influence various observational relations linking the properties of exoplanets to the characteristics of the host stars, for example the giant planet-metallicity relation. Aims. In this framework, we aim to expand our knowledge of the chemical composition of intermediate-age stars and understand whether these peculiarities are real or related to spectroscopic analysis techniques. Methods. We analysed high-resolution optical and near-infrared spectra of intermediate-age stars (<700 Myr) that have been observed simultaneously with HARPS-N and GIANO-B spectrographs in GIARPS mode. To overcome issues related to the young ages of the stars, we applied a new spectroscopic method that uses titanium lines to derive the atmospheric parameters, in particular surface gravities and microturbulence velocity parameter. We derived abundances of C I, Na I, Mg I, Al I, Si I, Ca I, Ti I, Ti II, Cr I, Cr II, Fe I, Fe II, Ni I, and Zn I. Results. The lack of systematic trends between elemental abundances and effective temperatures validates our methods. However, we observed that the coolest stars in the sample, where Teff < 5400 K, display higher abundances for the ionised species, in particular Cr II, and for high-excitation potential C I lines. Conclusions. We found a positive correlation between the higher abundances measured of C I and Cr II and the activity index log RHK′. Instead, we found no correlations between the C abundances obtained from CH molecular band at 4300 Å and both effective temperatures and activity. Thus, we suggest that these are better estimates for C abundances in young and cool stars. Finally, we found an indication of an increasing abundance ratio [X/H] with the condensation temperature for HD 167389, indicating possible episodes of planet engulfment.

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Section: Introductionsupporting

confidence: 53%

The GAPS Programme at TNG

Baratella

D’Orazi

Biazzo

et al. 2020

A&A

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“…Aleo et al (2017) argue that the large differences between Fe i and Fe i may be related to blending of Fe ii lines that become more severe at decreasing T eff . These results were corroborated by Takeda & Honda (2020), who also concluded that the O i overabundance obtained from the oxygen triplet by Schuler et al (2006) might be due to the different T eff scale and to over-estimation of the strength of the lines in coolest stars. Even though we are aware of the issues related to the spectroscopic analysis of young and cool stars and we are starting to shed light on the topic, we still lack a definitive solution.…”

Section: Introductionsupporting

confidence: 53%

The GAPS Programme at TNG -- XXV. Stellar atmospheric parameters and chemical composition through GIARPS optical and near-infrared spectra

Baratella,

D'Orazi,

Biazzo

et al. 2020

Preprint

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Context. The detailed chemical composition of stars is important in many astrophysical fields, among which is the characterisation of exoplanetary systems. Previous studies seem to indicate an anomalous chemical pattern of the youngest stellar population in the solar vicinity that has sub-solar metal content. This can influence various observational relations linking the properties of exoplanets to the characteristics of the host stars, for example the giant planet-metallicity relation. Aims. In this framework, we aim to expand our knowledge of the chemical composition of intermediate-age stars and understand whether these peculiarities are real or related to spectroscopic analysis techniques. Methods. We analysed high-resolution optical and near-infrared spectra of intermediate-age stars (< 700 Myr) that have been observed simultaneously with HARPS-N and GIANO-B spectrographs in GIARPS mode. To overcome issues related to the young ages of the stars, we applied a new spectroscopic method that uses titanium lines to derive the atmospheric parameters, in particular surface gravities and microturbulence velocity parameter. We derived abundances of C i, Na i, Mg i, Al i, Si i, Ca i, Ti i, Ti ii, Cr i, Cr ii, Fe i, Fe ii, Ni i, and Zn i.Results. The lack of systematic trends between elemental abundances and effective temperatures validates our methods. However, we observed that the coolest stars in the sample, where T eff < 5400 K, display higher abundances for the ionised species, in particular Cr ii, and for high-excitation potential C i lines. Conclusions. We found a positive correlation between the higher abundances measured of C i and Cr ii and the activity index logR HK . Instead, we found no correlations between the C abundances obtained from CH molecular band at 4300Å and both effective temperatures and activity. Thus, we suggest that these are better estimates for C abundances in young and cool stars. Finally, we found an indication of an increasing abundance ratio [X/H] with the condensation temperature for HD 167389, indicating possible episodes of planet engulfment.

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“…Actually, the mean abundance (⟨ A N ⟩ = 2.56 ± 0.10) derived for 18 stars of T eff < 5,500 K is consistent with the expected primordial Rb abundance of this cluster ( A s.s. + [Fe/H] Hyades ), where A s.s. is the solar system abundance (2.36) and [Fe/H] Hyades is the Hyades metallicity (≃ +0.2; cf. Takeda & Honda 2020).…”

Section: Discussionmentioning

confidence: 99%

“…dPrevious papers of the author that describe the observational data and atmospheric parameters of each star: TH20 ⋯ Takeda & Honda (2020), T05b ⋯ Takeda et al (2005b), T05a ⋯ Takeda et al (2005a), T15 ⋯ Takeda et al (2015), TSM08 ⋯ Takeda et al (2008). …”

Section: Program Stars and Their Parametersmentioning

confidence: 99%

“…Regarding determinations of Rb abundances and related quantities, the resonance Rb( I) line at 7,800 Å (which comprises multiple components and is blended with the Si( I) line) is exclusively used in this study. The procedures are essentially the same as those adopted in the author's previous papers (e.g., Takeda et al 2015; Takeda & Honda 2020; Takeda & Kawanomoto 2005). First, by applying Takeda's (1995) numerical algorithm, the best fit between the synthetic and observed spectra is accomplished in the specified wavelength region (7,776–7,804 Å) while varying the abundances of important elements ( A (Ni), A (Si), A (Rb), and A (Fe) in the present case), v M (macrobroadening velocity), and Δ λ (radial velocity or wavelength shift).…”

Section: Abundance Determinationmentioning

confidence: 99%

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Rubidium abundances of galactic disk stars

Takeda

2021

Astron Nachr

Self Cite

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Spectroscopic determinations of rubidium abundances were made by applying the spectrum-fitting method to the Rb(i) 7800 line for an extensive sample of ∼500 late-type dwarfs as well as giants (including Hyades cluster stars) belonging to the galactic disk population, with the aim of establishing the behavior of [Rb/Fe] ratio for disk stars in the metallicity range of −0.6 ≲ [Fe/H] ≲ +0.3. An inspection of the resulting Rb abundances for Hyades dwarfs revealed that they show a systematic T eff -dependent trend at ≳ 5,500 K; this means that the results for mid-G to F stars (including the Sun) are not reliable (i.e., more or less overestimated), which might be due to some imperfect treatment of surface convection in classical model atmospheres. As such, it was decided to confine only to late-G and K stars at T eff ≲ 5,500 K and adopt the solar-system (meteoritic) value as the reference Rb abundance. The [Rb/Fe] versus [Fe/H] relations derived for field dwarfs and giants turned out to be consistent with each other, showing a gradual increase of [Rb/Fe] with a decrease in [Fe/H] (with d[Rb/Fe]/d[Fe/H] gradient of ∼ −0.4 around the solar metallicity), which compares favorably with the theoretical prediction of chemical evolution models. Accordingly, this study could not confirm the anomalous behavior of [Rb/Fe] ratio (tending to be subsolar but steeply increasing towards supersolar metallicity) recently reported for M dwarf stars of −0.3 ≲ [Fe/H] ≲ +0.3.

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Spectroscopic Determination of Stellar Parameters and Oxygen Abundances for Hyades/Field G–K Dwarfs

Cited by 12 publications

References 40 publications

The GAPS Programme at TNG

The GAPS Programme at TNG

The GAPS Programme at TNG -- XXV. Stellar atmospheric parameters and chemical composition through GIARPS optical and near-infrared spectra

Rubidium abundances of galactic disk stars

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