atomic data Ca I and Ca II (trac #403)

reported by: @CloudyLex

Title:  
Influence of inelastic collisions with hydrogen atoms on the non-LTE modelling of Ca i and Ca ii lines in late-type stars
Authors:    
Mashonkina, L.; Sitnova, T.; Belyaev, A. K.
Affiliation:    
AA(Universitäts-Sternwarte München, Scheinerstr. 1, 81679, München, Germany lyuda@usm.lmu.de; Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya st. 48, 119017, Moscow, Russia lima@inasan.ru), AB(Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya st. 48, 119017, Moscow, Russia), AC(Herzen University, Moika 48, 191186, St. Petersburg, Russia)
Publication:    
Astronomy & Astrophysics, Volume 605, id.A53, 12 pp. (A&A Homepage)
Publication Date:   
09/2017
Origin: 
EDP Sciences
Astronomy Keywords: 
line: formation, stars: abundances, stars: atmospheres, stars: late-type
DOI:    
10.1051/0004-6361/201731236
Bibliographic Code: 
2017A&A...605A..53M
Abstract

We performed the non-local thermodynamic equilibrium (non-LTE, NLTE) calculations for Ca i-ii with the 
updated model atom that includes new quantum-mechanical rate coefficients for Ca i + H i collisions from 
two recent studies and investigated the accuracy of calcium abundance determinations using the Sun, 
Procyon, and five metal-poor (MP, -2.6 ≤ [Fe/H] ≤-1.3) stars with well-determined stellar parameters. 
Including H i collisions substantially reduces over-ionisation of Ca i in the line formation layers compared 
with the case of pure electronic collisions and thus the NLTE effects on abundances derived from Ca i lines. 
We show that both collisional recipes lead to very similar NLTE results. As for Ca ii, the classical Drawinian 
rates scaled by SH = 0.1 are still applied. When using the subordinate lines of Ca i and the high-excitation 
lines of Ca ii, NLTE provides the smaller line-to-line scatter compared with the LTE case for each star. For 
Procyon, NLTE removes a steep trend with line strength among strong Ca i lines seen in LTE and leads to 
consistent [Ca/H] abundances from the two ionisation stages. In the MP stars, the NLTE abundance from 
Ca ii 8498 Å agrees well with the abundance from the Ca i subordinate lines, in contrast to LTE, where the 
abundance difference grows towards lower metallicity and reaches 0.46 dex in BD -13°3442 ([Fe/H] = 
-2.62). NLTE largely removes abundance discrepancies between the high-excitation lines of Ca ii and Ca ii 
8498 Å obtained for our four [Fe/H] < -2 stars under the LTE assumption. We investigated the formation of 
the Ca i resonance line in the [Fe/H] < -2 stars. When the calcium abundance varies between [Ca/H] ≃ -1.8 
and -2.3, photon loss in the resonance line itself in the uppermost atmospheric layers drives the 
strengthening of the line core compared with the LTE case, and this effect prevails over the weakening of 
the line wings, resulting in negative NLTE abundance correction and underestimation of the abundance 
derived from Ca i 4226 Å compared with that from the subordinate lines, by 0.08 to 0.32 dex. This problem 
may be related to the use of classical homogeneous (1D) model atmospheres. The situation is improved 
when the calcium abundance decreases and the Ca i 4226 Å line formation depths are shifted into deep 
atmospheric layers that are dominated by over-ionisation of Ca i. However, the departures from LTE are still 
underestimated for Ca i 4226 Å at [Ca/H] ≃ -4.4 (HE 0557-4840). Consistent NLTE abundances from the 
Ca i resonance line and the Ca ii lines are found for HE 0107-5240 and HE 1327-2326 with [Ca/H] ≤-5. 
Thus, the Ca i/Ca ii ionisation equilibrium method can successfully be applied to determine surface gravities 
of [Ca/H] ≾ -5 stars. We provide the NLTE abundance corrections for 28 lines of Ca i in a grid of model 
atmospheres with 5000 K ≤ Teff ≤ 6500 K, 2.5 ≤ log g ≤ 4.5, -4 ≤ [Fe/H] ≤ 0, which is suitable for 
abundance analysis of FGK-type dwarfs and subgiants.

Migrated from https://www.nublado.org/ticket/403

{
    "status": "new",
    "changetime": "2019-02-04T13:02:49Z",
    "_ts": "1549285369825011",
    "description": "{{{\nTitle:\t\nInfluence of inelastic collisions with hydrogen atoms on the non-LTE modelling of Ca i and Ca ii lines in late-type stars\nAuthors:\t\nMashonkina, L.; Sitnova, T.; Belyaev, A. K.\nAffiliation:\t\nAA(Universit\u00e4ts-Sternwarte M\u00fcnchen, Scheinerstr. 1, 81679, M\u00fcnchen, Germany lyuda@usm.lmu.de; Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya st. 48, 119017, Moscow, Russia lima@inasan.ru), AB(Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya st. 48, 119017, Moscow, Russia), AC(Herzen University, Moika 48, 191186, St. Petersburg, Russia)\nPublication:\t\nAstronomy & Astrophysics, Volume 605, id.A53, 12 pp. (A&A Homepage)\nPublication Date:\t\n09/2017\nOrigin:\t\nEDP Sciences\nAstronomy Keywords:\t\nline: formation, stars: abundances, stars: atmospheres, stars: late-type\nDOI:\t\n10.1051/0004-6361/201731236\nBibliographic Code:\t\n2017A&A...605A..53M\nAbstract\n\nWe performed the non-local thermodynamic equilibrium (non-LTE, NLTE) calculations for Ca i-ii with the \nupdated model atom that includes new quantum-mechanical rate coefficients for Ca i + H i collisions from \ntwo recent studies and investigated the accuracy of calcium abundance determinations using the Sun, \nProcyon, and five metal-poor (MP, -2.6 \u2264 [Fe/H] \u2264-1.3) stars with well-determined stellar parameters. \nIncluding H i collisions substantially reduces over-ionisation of Ca i in the line formation layers compared \nwith the case of pure electronic collisions and thus the NLTE effects on abundances derived from Ca i lines. \nWe show that both collisional recipes lead to very similar NLTE results. As for Ca ii, the classical Drawinian \nrates scaled by SH = 0.1 are still applied. When using the subordinate lines of Ca i and the high-excitation \nlines of Ca ii, NLTE provides the smaller line-to-line scatter compared with the LTE case for each star. For \nProcyon, NLTE removes a steep trend with line strength among strong Ca i lines seen in LTE and leads to \nconsistent [Ca/H] abundances from the two ionisation stages. In the MP stars, the NLTE abundance from \nCa ii 8498 \u00c5 agrees well with the abundance from the Ca i subordinate lines, in contrast to LTE, where the \nabundance difference grows towards lower metallicity and reaches 0.46 dex in BD -13\u00b03442 ([Fe/H] = \n-2.62). NLTE largely removes abundance discrepancies between the high-excitation lines of Ca ii and Ca ii \n8498 \u00c5 obtained for our four [Fe/H] < -2 stars under the LTE assumption. We investigated the formation of \nthe Ca i resonance line in the [Fe/H] < -2 stars. When the calcium abundance varies between [Ca/H] \u2243 -1.8 \nand -2.3, photon loss in the resonance line itself in the uppermost atmospheric layers drives the \nstrengthening of the line core compared with the LTE case, and this effect prevails over the weakening of \nthe line wings, resulting in negative NLTE abundance correction and underestimation of the abundance \nderived from Ca i 4226 \u00c5 compared with that from the subordinate lines, by 0.08 to 0.32 dex. This problem \nmay be related to the use of classical homogeneous (1D) model atmospheres. The situation is improved \nwhen the calcium abundance decreases and the Ca i 4226 \u00c5 line formation depths are shifted into deep \natmospheric layers that are dominated by over-ionisation of Ca i. However, the departures from LTE are still \nunderestimated for Ca i 4226 \u00c5 at [Ca/H] \u2243 -4.4 (HE 0557-4840). Consistent NLTE abundances from the \nCa i resonance line and the Ca ii lines are found for HE 0107-5240 and HE 1327-2326 with [Ca/H] \u2264-5. \nThus, the Ca i/Ca ii ionisation equilibrium method can successfully be applied to determine surface gravities \nof [Ca/H] \u227e -5 stars. We provide the NLTE abundance corrections for 28 lines of Ca i in a grid of model \natmospheres with 5000 K \u2264 Teff \u2264 6500 K, 2.5 \u2264 log g \u2264 4.5, -4 \u2264 [Fe/H] \u2264 0, which is suitable for \nabundance analysis of FGK-type dwarfs and subgiants.\n\n}}}",
    "reporter": "gary",
    "cc": "",
    "resolution": "",
    "time": "2017-11-03T17:22:22Z",
    "component": "atomic/molecular data base",
    "summary": "atomic data Ca I and Ca II",
    "priority": "good to do",
    "keywords": "",
    "version": "",
    "milestone": "no milestone",
    "owner": "nobody",
    "type": "enhancement"
}

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atomic data Ca I and Ca II (trac #403) #405