J/A+A/631/A43 Late-type stars FeI & FeII NLTE line formation (Mashonkina+, 2019)
Influence of inelastic collisions with hydrogen atoms on the non-LTE line
formation for Fe I and Fe II in the 1D model atmospheres of late-type stars.
Mashonkina L., Sitnova T., Yakovleva S.A., Belyaev A.K.
<Astron. Astrophys. 631, A43 (2019)>
=2019A&A...631A..43M 2019A&A...631A..43M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Abundances ; Models, atmosphere
Keywords: atomic processes - stars: abundances - stars: atmospheres -
stars: late-type = line: formation
Abstract:
Iron plays a crucial role in studies of late-type stars. In their
atmospheres, neutral iron is the minority species and lines of FeI are
subject to the departures from local thermodynamic equilibrium (LTE).
In contrast, one believes that LTE is a realistic approximation for
FeII lines. The main source of the uncertainties in the non-LTE (NLTE)
calculations for cool atmospheres is a treatment of inelastic
collisions with hydrogen atoms. We investigate the effect of FeI+HI
and FeII+HI collisions and their different treatment on the FeI/FeII
ionisation equilibrium and iron abundance determinations for Galactic
halo benchmark stars HD 84937, HD 122563, and HD 140283 and a sample
of 38 very metal-poor (VMP) giants in the dwarf galaxies with well
known distances. We perform the NLTE calculations for FeI-FeII with
applying quantum-mechanical rate coefficients for collisions with HI
from recent papers of Barklem (2018, Cat. J/A+A/612/A90B18),
Yakovleva, Belyaev, and Kraemer (2018CP....515..369Y 2018CP....515..369Y, YBK18), and
Yakovleva, Belyaev, and Kraemer (2019MNRAS.483.5105Y 2019MNRAS.483.5105Y , YBK19). We find
that collisions with HI serve as efficient thermalisation processes
for FeII, such that the NLTE abundance corrections for FeII lines do
not exceed 0.02dex, in absolute value, for [Fe/H]~>-3 and reach
+0.06dex at [Fe/H]~-4. For a given star, different treatments of
FeI+HI collisions by B18 and YBK18 lead to similar average NLTE
abundances from the FeI lines, although there exist discrepancies in
the NLTE abundance corrections for individual lines. With using
quantum-mechanical collisional data and the Gaia based surface
gravity, we obtain consistent abundances from the two ionisation
stages, FeI and FeII, for a red giant HD 122563. For a turn-off star
HD 84937 and a subgiant HD 140283, we analyse the iron lines in the
visible and the ultra-violet (UV, 1968 to 2990Å) range. For either
FeI or FeII, abundances from the visible and UV lines are found to be
consistent in each star. The NLTE abundances from the two ionisation
stages agree within 0.10dex, when using the YBK18 data, and 0.13dex in
case of B18. The FeI/FeII ionisation equilibrium is achieved for each
star of our stellar sample in the dwarf galaxies, with the exception
of stars at [Fe/H]~←3.7.
Description:
Table 2 presents the two sets of the NLTE abundances from lines of Fe
I and Fe II in HD 84937, HD 140283, and HD 122563 based on high
resolution spectra from the UVESPOP archive. Table 4 presents the iron
NLTE abundances of the dSph stars based on the observed equivalent
widths from Mashonkina et al. (2017, Cat. J/A+A/604/A129).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 50 41 List of studied stars
table2.dat 99 151 LTE and NLTE abundances of three halo stars
table4.dat 85 38 LTE and NLTE abundances of the dSph stars
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See also:
J/A+A/604/A129 : Formation of MW halo and its dwarf satellites (Mashonkina+,
J/ApJ/817/53 : Fe-group elemental abundance analysis in HD84937
(Sneden+, 2016)
J/ApJ/860/125 : Six warm metal-poor stars iron abundances (Roederer+, 2018)
J/A+A/612/A90 : Inelastic Fe+H collision data (Barklem, 2018)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Star Star designation
16- 17 I2 h RAh Right ascension (J2000)
19- 20 I2 min RAm Right ascension (J2000)
22- 26 F5.2 s RAs Right ascension (J2000)
28 A1 --- DE- Declination sign (J2000)
29- 30 I2 deg DEd Declination (J2000)
32- 33 I2 arcmin DEm Declination (J2000)
35- 38 F4.1 arcsec DEs Declination (J2000)
41- 50 A10 --- FileName Name of the table with data for this star
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- El Atom
4- 5 A2 --- Ion Ion
7- 13 F7.2 0.1nm lambda Wavelength
15- 18 F4.2 eV Eexc Excitation energy
20- 24 F5.2 --- loggf Adopted gf-value
27- 31 F5.1 0.1pm EW1 ? Equivalent width in HD 84937
33- 37 F5.2 --- epsLTE1 ? HD 84937 LTE abundance (log eps(H)=12)
39- 43 F5.2 --- epsNLTEB1 ? HD 84937 NLTE abundance (log eps(H)=12),
B18 recipe
45- 49 F5.2 --- epsNLTEY1 ? HD 84937 NLTE abundance (log eps(H)=12),
YBK18
52- 56 F5.1 0.1pm EW2 ? Equivalent width in HD 140283
58- 62 F5.2 --- epsLTE2 ? HD 140283 LTE abundance (log eps(H)=12)
64- 68 F5.2 --- epsNLTEB2 ? HD 140283 NLTE abundance (log eps(H)=12),
B18 recipe
70- 74 F5.2 --- epsNLTEY2 ? HD 140283 NLTE abundance (log eps(H)=12),
YBK18
77- 81 F5.1 0.1pm EW3 ? Equivalent width in HD 122563
83- 87 F5.2 --- epsLTE3 ? HD 122563LTE abundance (log eps(H)=12)
89- 93 F5.2 --- epsNLTEB3 ? HD 122563NLTE abundance (log eps(H)=12),
B18 recipe
95- 99 F5.2 --- epsNLTEY3 ? HD 122563NLTE abundance (log eps(H)=12),
YBK18
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Star Star designation
16- 19 I4 K Teff Effective temperature
21- 24 F4.2 [cm/s2] logg Surface gravity
26- 30 F5.2 --- [Fe/H] Metallicity
32- 34 F3.1 km/s xi Microturbulent velocity
37- 38 I2 --- NFeI Number of FeI lines
40- 41 I2 --- NFeII Number of FeII lines
44- 47 F4.2 --- epsL1 Mean FeI LTE abundance (log eps(H)=12)
49- 52 F4.2 --- e_epsL1 Dispersion of FeI LTE abundance
55- 58 F4.2 --- epsL2 Mean FeII LTE abundance (log eps(H)=12)
60- 63 F4.2 --- e_epsL2 Dispersion of FeII LTE abundance
66- 69 F4.2 --- epsN1 Mean FeI NLTE abundance (log eps(H)=12)
71- 74 F4.2 --- e_epsN1 Dispersion of FeI NLTE abundance
77- 80 F4.2 --- epsN2 Mean FeII NLTE abundance (log eps(H)=12)
82- 85 F4.2 --- e_epsN2 Dispersion of FeII NLTE abundance
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Acknowledgements:
Lyudmila Mashonkina, lima(at)inasan.ru
References:
Mashonkina et al., 2011A&A...528A..87M 2011A&A...528A..87M
Mashonkina et al, 2017A&A...604A.129M 2017A&A...604A.129M, Cat. J/A+A/604/A129
Yakovleva et al., 2018CP....515..369Y 2018CP....515..369Y, YBK18
(End) Lyudmila Mashonkina [INASAN, Russia], Patricia Vannier [CDS] 16-Sep-2019