3D hydrodynamical CO5BOLD model atmospheres of late-type giants: stellar abundances from molecular lines

Ivanauskas, A.; Kučinskas, A.; Ludwig, H. G.; Caffau, E.

doi:10.22323/1.100.0290

Cited by 7 publications

(9 citation statements)

References 4 publications

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“…Remarkably, at [M/H] = −3.0 this may result in differences A&A 549, A14 (2013) of up to −1.0 dex in the abundances of chemical elements derived with the 3D hydrodynamical and classical 1D model atmospheres. This result was later confirmed by Dobrovolskas et al (2010) and Ivanauskas et al (2010), who used different 3D hydrodynamical stellar atmosphere and spectrum synthesis codes, CO 5 BOLD and Linfor3D, respectively, together with the atmospheric parameters of red giants similar to those utilized by Collet et al (2007). All these studies unequivocally point to the fact that the role of convection in the atmospheres of red giant stars may be significantly more important than previously thought, especially at metallicities [M/H] < ∼ −1.0.…”

Section: Introductionmentioning

confidence: 53%

“…This approach allowed us to cover a range in λ c and χ to quantify the trends of line formation properties in the 3D hydrodynamical and 1D classical model atmospheres with respect to these two line parameters. Conceptually, this method can be traced back to the work of Steffen & Holweger (2002) and was applied in several later studies too (e.g., Collet et al 2007;Dobrovolskas et al 2010;Ivanauskas et al 2010). Synthetic line profiles were calculated for the following tracer species of astrophysical interest: Fictitious lines were calculated at three wavelengths, λ c = 400, 850, and 1600 nm.…”

Section: One-dimensional (1d) Modelmentioning

confidence: 99%

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Three-dimensional hydrodynamical CO⁵BOLD model atmospheres of red giant stars

Kučinskas¹,

Steffen²,

Ludwig³

et al. 2012

A&A

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Aims. We investigate the role of convection in the formation of atomic and molecular lines in the atmosphere of a red giant star. For this purpose we study the formation properties of spectral lines that belong to a number of astrophysically important tracer elements, including neutral and singly ionized atoms (Li Ba ii, and Eu ii), and molecules (CH, CO, C 2 , NH, CN, and OH).Methods. We focus our investigation on a prototypical red giant located close to the red giant branch (RGB) tip (T eff = 3660 K, log g = 1.0, [M/H] = 0.0). We used two types of model atmospheres, 3D hydrodynamical and classical 1D, calculated with the CO 5 BOLD and LHD stellar atmosphere codes, respectively. Both codes share the same atmospheric parameters, chemical composition, equation of state, and opacities, which allowed us to make a strictly differential comparison between the line formation properties predicted in 3D and 1D. The influence of convection on the spectral line formation was assessed with the aid of 3D-1D abundance corrections, which measure the difference between the abundances of chemical species derived with the 3D hydrodynamical and 1D classical model atmospheres. Results. We find that convection plays a significant role in the spectral line formation in this particular red giant. The derived 3D-1D abundance corrections rarely exceed ±0.1 dex when lines of neutral atoms and molecules are considered, which is in line with the previous findings for solar-metallicity red giants located on the lower RGB. The situation is different with lines that belong to ionized atoms, or to neutral atoms with high ionization potential. In both cases, the corrections for high-excitation lines (χ > 8 eV) may amount to Δ 3D−1D ∼ −0.4 dex. The 3D-1D abundance corrections generally show a significant wavelength dependence; in most cases they are smaller in the near-infrared, at 1600-2500 nm.

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Section: Introductionmentioning

confidence: 53%

Section: One-dimensional (1d) Modelmentioning

confidence: 99%

Three-dimensional hydrodynamical CO⁵BOLD model atmospheres of red giant stars

Kučinskas¹,

Steffen²,

Ludwig³

et al. 2012

A&A

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“…Even considering that the atmospheric parameters are not exactly the same in both their and our models, the corrections of Collet and collaborators appear noticeably larger. This is also the case for other species (see Ivanauskas et al 2010;Dobrovolskas et al 2010) and the reason is not yet understood.…”

Section: Abundance Corrections For the Hf R9 And Forbidden O Linesmentioning

confidence: 94%

Fluorine Abundances of Galactic Low-Metallicity Giants

Ludwig

Caffau

et al. 2013

ApJ

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With abundances and 2σ upper limits of fluorine (F) in seven metal-poor field giants, nucleosynthesis of stellar F at low metallicity is discussed. The measurements are derived from the HF(1-0) R9 line at 23358 Å using nearinfrared K-band high-resolution spectra obtained with CRIRES at the Very Large Telescope. The sample reaches lower metallicities than previous studies on F of field giants, ranging from [Fe/H] = −1.56 down to −2.13. Effects of three-dimensional model atmospheres on the derived F and O abundances are quantitatively estimated and shown to be insignificant for the program stars. The observed F yield in the form of [F/O] is compared with two sets of Galactic chemical evolution models, which quantitatively demonstrate the contribution of Type II supernova (SN II) ν-process and asymptotic giant branch/Wolf-Rayet stars. It is found that at this low-metallicity region, models cannot well predict the observed distribution of [F/O], while the observations are better fit by models considering an SN II ν-process with a neutrino energy of E ν = 3 × 10 53 erg. Our sample contains HD 110281, a retrograde orbiting low-α halo star, showing a similar F evolution as globular clusters. This supports the theory that such halo stars are possibly accreted from dwarf galaxy progenitors of globular clusters in the halo.

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“…When the original log g f by Kurucz are applied, the synthetic CN lines of Arcturus are far too strong with respect to the observed ones. Molecular lines are known to be prone to NLTE effects (Hinkle & Lambert 1975;Schweitzer et al 2003;Plez 2008) and 3D effects (Ivanauskas et al 2010), and their strengths may not be correctly reproduced under 1D LTE assumption. In order to match the strenghts of the CN lines observed on the Sun and on Arcturus at the same time we needed to set the We believe that Arcturus' low C and N abundances found by us merely counterbalance the 3D NLTE effects that we could not take in account.…”

Section: The Molecular Linesmentioning

confidence: 99%

SP_Ace: a new code to derive stellar parameters and elemental abundances

Boeche

Grebel

2016

A&A

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Context. Ongoing and future massive spectroscopic surveys will collect large numbers (10 6 -10 7 ) of stellar spectra that need to be analyzed. Highly automated software is needed to derive stellar parameters and chemical abundances from these spectra. Aims. We developed a new method of estimating the stellar parameters T eff , log g, [M/H], and elemental abundances. This method was implemented in a new code, SP_Ace (Stellar Parameters And Chemical abundances Estimator). This is a highly automated code suitable for analyzing the spectra of large spectroscopic surveys with low or medium spectral resolution (R = 2000-20 000). Methods. After the astrophysical calibration of the oscillator strengths of 4643 absorption lines covering the wavelength ranges 5212-6860 Å and 8400-8924 Å, we constructed a library that contains the equivalent widths (EW) of these lines for a grid of stellar parameters. The EWs of each line are fit by a polynomial function that describes the EW of the line as a function of the stellar parameters. The coefficients of these polynomial functions are stored in a library called the "GCOG library". SP_Ace, a code written in FORTRAN95, uses the GCOG library to compute the EWs of the lines, constructs models of spectra as a function of the stellar parameters and abundances, and searches for the model that minimizes the χ 2 deviation when compared to the observed spectrum. The code has been tested on synthetic and real spectra for a wide range of signal-to-noise and spectral resolutions. Results. SP_Ace derives stellar parameters such as T eff , log g, [M/H], and chemical abundances of up to ten elements for low to medium resolution spectra of FGK-type stars with precision comparable to the one usually obtained with spectra of higher resolution. Systematic errors in stellar parameters and chemical abundances are presented and identified with tests on synthetic and real spectra. Stochastic errors are automatically estimated by the code for all the parameters. A simple Web front end of SP_Ace can be found at http://dc.g-vo.org/SP_ACE, while the source code will be published soon.

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3D hydrodynamical CO5BOLD model atmospheres of late-type giants: stellar abundances from molecular lines

Cited by 7 publications

References 4 publications

Three-dimensional hydrodynamical CO⁵BOLD model atmospheres of red giant stars

Three-dimensional hydrodynamical CO⁵BOLD model atmospheres of red giant stars

Fluorine Abundances of Galactic Low-Metallicity Giants

SP_Ace: a new code to derive stellar parameters and elemental abundances

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3D hydrodynamical CO5BOLD model atmospheres of late-type giants: stellar abundances from molecular lines

Cited by 7 publications

References 4 publications

Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars

Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars

Fluorine Abundances of Galactic Low-Metallicity Giants

SP_Ace: a new code to derive stellar parameters and elemental abundances

Contact Info

Product

Resources

About

Three-dimensional hydrodynamical CO⁵BOLD model atmospheres of red giant stars

Three-dimensional hydrodynamical CO⁵BOLD model atmospheres of red giant stars