Influence of inelastic collisions with hydrogen atoms on the formation of AlI and SiI lines in stellar spectra

	Influence of inelastic collisions with hydrogen atoms on the formation of AlI and SiI lines in stellar spectra
	Mashonkina, L. I.1; Belyaev, A. K.2; Shi, J. -R.3
刊名	ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS
	2016-06-01
卷号	42 期号:6 页码:366-378
关键词	stellar atmospheres spectral line formation energy level excitation and charge exchange in inelastic collisions aluminum abundance in stars
英文摘要	We have performed calculations by abandoning the assumption of local thermodynamic equilibrium (within the so-called non-LTE approach) for Al I and Si I with model atmospheres corresponding to stars of spectral types F-G-Kwith differentmetal abundances. To take into account inelastic collisions with hydrogen atoms, for the first time we have applied the cross sections calculated by Belyaev et al. using model approaches within the formalism of the Born-Oppenheimer quantum theory. We show that for Al I non-LTE leads to higher ionization (overionization) than in LTE in the spectral line formation region and to a weakening of spectral lines, which is consistent with earlier non-LTE studies. However, our results, especially for the subordinate lines, differ quantitatively from the results of predecessors. Owing to their large cross sections, the ion-pair production and mutual neutralization processes Al I(nl) + HI(1s) a dagger" Al II(3s (2)) + H- provide a close coupling of highly excited Al I levels with the Al II ground state, which causes the deviations from the equilibrium level population to decrease compared to the calculations where the collisions only with electrons are taken into account. For three moderately metal-deficient dwarf stars, the aluminum abundance has been determined from seven Al I lines in different models of their formation. Under the assumption of LTE and in non-LTE calculations including the collisions only with electrons, the Al I 3961 EeA resonance line gives a systematically lower abundance than the mean abundance from the subordinate lines, by 0.25-0.45 dex. The difference for each star is removed by taking into account the collisions with hydrogen atoms, and the rms error of the abundance derived from all seven Al I lines decreases by a factor of 1.5-3 compared to the LTE analysis. We have calculated the non- LTE corrections to the abundance for six subordinate Al I lines as a function of the effective temperature (4500 K a parts per thousand currency sign T (eff) a parts per thousand currency sign 6500 K), surface gravity (3.0 a parts per thousand currency sign log g a parts per thousand currency sign 4.5), and metal abundance ([M/H] = 0, -1, -2, and -3). For Si I including the collisions with HI leads to the establishment of equilibrium populations in the spectral line formation region even in hot metal-deficient models and to vanishingly small departures from LTE in spectral lines.
收录类别	SCI
语种	英语
WOS记录号	WOS:000377938600003
内容类型	期刊论文
源URL	[http://ir.bao.ac.cn/handle/114a11/5320]
专题	国家天文台_光学天文研究部
作者单位	1.Russian Acad Sci, Inst Astron, Pyatnitskaya Ul 48, Moscow 109017, Russia 2.Herzen State Pedag Univ, Kazanskaya Ul 5, St Petersburg 191186, Russia 3.Chinese Acad Sci, Natl Astron Observ, A20 Datun Rd, Beijing 100012, Peoples R China
推荐引用方式 GB/T 7714	Mashonkina, L. I.,Belyaev, A. K.,Shi, J. -R.. Influence of inelastic collisions with hydrogen atoms on the formation of AlI and SiI lines in stellar spectra[J]. ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS,2016,42(6):366-378.
APA	Mashonkina, L. I.,Belyaev, A. K.,&Shi, J. -R..(2016).Influence of inelastic collisions with hydrogen atoms on the formation of AlI and SiI lines in stellar spectra.ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS,42(6),366-378.
MLA	Mashonkina, L. I.,et al."Influence of inelastic collisions with hydrogen atoms on the formation of AlI and SiI lines in stellar spectra".ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS 42.6(2016):366-378.