Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

Marfil, E.; Tabernero, H. M.; Montes, D.; Caballero, J. A.; Soto, M. G.; Hernández, J. I. González; Kaminski, A.; Nagel, E.; Jeffers, S. V.; Reiners, A.; Ribas, I.; Quirrenbach, A.; Amado, P. J.

doi:10.1093/mnras/staa058

Cited by 18 publications

(15 citation statements)

References 100 publications

(120 reference statements)

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“…The spectra show a prominent He I IR line along with a Si I line at 10 830.057 Å and a Na I line at 10 837.814 Å. All other spectral features in the shown wavelength range remain unidentified; see a discussion in Fuhrmeister et al (2019a) and compare to Andreasen et al (2016) and Marfil et al (2020). Figure 1 also shows that telluric lines are a minor problem around the Hα line.…”

Section: He I Ir Line Variabilitymentioning

confidence: 89%

The CARMENES search for exoplanets around M dwarfs

Fuhrmeister

Czesla

Hildebrandt

et al. 2020

A&A

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The He I infrared (IR) triplet at 10 830 Å is known as an activity indicator in solar-type stars and has become a primary diagnostic in exoplanetary transmission spectroscopy. He I IR lines are a tracer of the stellar extreme-ultraviolet irradiation from the transition region and corona. We study the variability of the He I triplet lines in a spectral time series of 319 M dwarf stars that was obtained with the CARMENES high-resolution optical and near-infrared spectrograph at Calar Alto. We detect He I IR line variability in 18% of our sample stars, all of which show Hα in emission. Therefore, we find detectable He I variability in 78% of the sub-sample of stars with Hα emission. Detectable variability is strongly concentrated in the latest spectral sub-types, where the He I lines during quiescence are typically weak. The fraction of stars with detectable He I variation remains lower than 10% for stars earlier than M3.0 V, while it exceeds 30% for the later spectral sub-types. Flares are accompanied by particularly pronounced line variations, including strongly broadened lines with red and blue asymmetries. However, we also find evidence for enhanced He I absorption, which is potentially associated with increased high-energy irradiation levels at flare onset. Generally, He I and Hα line variations tend to be correlated, with Hα being the most sensitive indicator in terms of pseudo-equivalent width variation. This makes the He I triplet a favourable target for planetary transmission spectroscopy.

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Section: He I Ir Line Variabilitymentioning

confidence: 89%

The CARMENES search for exoplanets around M dwarfs

Fuhrmeister

Czesla

Hildebrandt

et al. 2020

A&A

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“…The low photospheric temperatures give rise to pervasive molecular bands that severely distort the stellar continuum (Kirkpatrick et al 1991;Tinney & Reid 1998;Reiners et al 2018). This alone rules out classical techniques commonly adopted in the analysis of solar-type spectra, such as the equivalent width (EW) method (Marfil et al 2020). Stellar convection in M dwarfs also calls into question some of the physical assumptions behind the model atmospheres of late-type stars, such as local thermodynamic equilibrium (LTE) and one-dimensional (1D) geometry for radiative transfer, which often represents a limitation to the interpretation at the resolution achieved by modern spectrographs (Bergemann et al 2017;Olander et al 2021).…”

Section: Introductionmentioning

confidence: 99%

The CARMENES search for exoplanets around M dwarfs. Stellar atmospheric parameters of target stars with SteParSyn

Marfil,

Tabernero,

Montes

et al. 2021

Preprint

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We determined effective temperatures, surface gravities, and metallicities for a sample of 343 M dwarfs observed with CARMENES, the double-channel, high-resolution spectrograph installed at the 3.5 m telescope at Calar Alto Observatory. We employed SteParSyn, a Bayesian spectral synthesis implementation particularly designed to infer the stellar atmospheric parameters of late-type stars following a Markov chain Monte Carlo approach. We made use of the BT-Settl model atmospheres and the radiative transfer code turbospectrum to compute a grid of synthetic spectra around 75 magnetically insensitive Fe i and Ti i lines plus the TiO γ and bands. To avoid any potential degeneracy in the parameter space, we imposed Bayesian priors on T eff and log g based on the comprehensive, multi-band photometric data available for the sample. We find that this methodology is suitable down to M7.0 V, where refractory metals such as Ti are expected to condense in the stellar photospheres. The derived T eff , log g, and [Fe/H] range from 3000 to 4200 K, 4.5 to 5.3 dex, and −0.7 to 0.2 dex, respectively. Although our T eff scale is in good agreement with the literature, we report large discrepancies in the [Fe/H] scales, which might arise from the different methodologies and sets of lines considered. However, our [Fe/H] is in agreement with the metallicity distribution of FGK-type stars in the solar neighbourhood and correlates well with the kinematic membership of the targets in the Galactic populations. Lastly, excellent agreement in T eff is found for M dwarfs with interferometric angular diameter measurements, as well as in the [Fe/H] between the components in the wide physical FGK+M and M+M systems included in our sample.

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“…Until recently, the study of stellar spectra mainly involved the analysis of data in the optical band, covering the wavelength range from ∼4000 to ∼7000 Å. However, the advent of high-resolution near-infrared (NIR) spectroscopy allowed us to extend the analysis of stellar spectra at longer wavelengths as well, and to test the validity of optical and NIR analysis techniques (Marfil et al 2020). This is particularly important in the study of young and intermediate-age stars, for which stellar activity and other effects can alter the derivation of atmospheric parameters and, specifically, the chemical composition.…”

Section: Introductionmentioning

confidence: 99%

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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Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

Cited by 18 publications

References 100 publications

The CARMENES search for exoplanets around M dwarfs

The CARMENES search for exoplanets around M dwarfs

The CARMENES search for exoplanets around M dwarfs. Stellar atmospheric parameters of target stars with SteParSyn

The GAPS Programme at TNG

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