J/ApJ/751/156 Ti and Fe lines in red supergiants (Bergemann+, 2012)
Red supergiant stars as cosmic abundance probes: NLTE effects in J-band iron
and titanium lines.
Bergemann M., Kudritzki R.-P., Plez B., Davies B., Lind K., Gazak Z.
<Astrophys. J., 751, 156 (2012)>
=2012ApJ...751..156B 2012ApJ...751..156B
ADC_Keywords: Stars, supergiant ; Models, atmosphere ; Abundances ;
Equivalent widths
Keywords: galaxies: abundances - line: formation - radiative transfer -
stars: abundances - stars: late-type - supergiants
Abstract:
Detailed non-LTE (NLTE) calculations for red supergiant (RSG) stars
are presented to investigate the influence of NLTE on the formation of
atomic iron and titanium lines in the J band. With their enormous
brightness at J band RSG stars are ideal probes of cosmic abundances.
Recent LTE studies have found that metallicities accurate to 0.15 dex
can be determined from medium-resolution spectroscopy of individual
RSGs in galaxies as distant as 10 Mpc. The NLTE results obtained in
this investigation support these findings. NLTE abundance corrections
for iron are smaller than 0.05 dex for effective temperatures between
3400 K and 4200 K and 0.1 dex at 4400 K. For titanium the NLTE
abundance corrections vary smoothly between -0.4 dex and +0.2 dex as a
function of effective temperature. For both elements, the corrections
also depend on stellar gravity and metallicity. The physical reasons
behind the NLTE corrections and the consequences for extragalactic
J-band abundance studies are discussed.
Description:
The atmospheric structure for our NLTE line formation calculations is
provided by the MARCS model atmospheres. The physical assumptions
underlying these atmospheres are described in Gustafsson et al.
(2008A&A...486..951G 2008A&A...486..951G). In short, these LTE models are spherically
symmetric, in one-dimensional (1D) hydrostatic equilibrium, and
include convection within the framework of the mixing-length theory.
The reference solar abundance mixture in these models is that of
Grevesse et al. (2007SSRv..130..105G 2007SSRv..130..105G). See section 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 52 45 Non-LTE abundance corrections for the TiI and
FeI lines (ξt=2km/s)
table3.dat 52 45 Non-LTE abundance corrections for the TiI and
FeI lines (ξt=5km/s)
table4.dat 94 45 Equivalent widths of the TiI and FeI lines
(ξt=2km/s)
table5.dat 94 45 Equivalent widths of the TiI and FeI lines
(ξt=5km/s)
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See also:
J/MNRAS/418/863 : NLTE corrections for Mg and Ca lines (Merle+ 2011)
J/A+A/503/541 : Neutral Li in late-type stars non-LTE calc. (Lind+, 2009)
J/A+A/350/955 : Atmosph. parameters in metal-poor stars. II (Gratton+, 1999)
Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
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1- 4 I4 K Teff [3400/4400] Effective temperature
6- 10 F5.2 [cm/s2] log(g) [-0.5/1] Log surface gravity
12- 16 F5.2 [Sun] [Z] [-0.5/0.5] Metallicity
18- 22 F5.2 [-] dA(TiI)1 TiI(11892.85) NLTE log(abundance) correction
24- 28 F5.2 [-] dA(TiI)2 TiI(11949.58) NLTE log(abundance) correction
30- 34 F5.2 [-] dA(FeI)1 FeI(11593.55) NLTE log(abundance) correction
36- 40 F5.2 [-] dA(FeI)2 FeI(11638.25) NLTE log(abundance) correction
42- 46 F5.2 [-] dA(FeI)3 FeI(11882.80) NLTE log(abundance) correction
48- 52 F5.2 [-] dA(FeI)4 FeI(11973.01) NLTE log(abundance) correction
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Byte-by-byte Description of file: table[45].dat
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Bytes Format Units Label Explanations
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1- 4 I4 K Teff [3400/4400] Effective temperature
6- 10 F5.2 [cm/s2] log(g) [-0.5/1] Log surface gravity
12- 16 F5.2 [Sun] [Z] [-0.5/0.5] Metallicity
18- 22 F5.1 10-13m W(TiI)1L TiI(11892) LTE equivalent width (mÅ)
24- 28 F5.1 10-13m W(TiI)1N TiI(11892) NLTE equivalent width (mÅ)
30- 34 F5.1 10-13m W(TiI)2L TiI(11949) LTE equivalent width (mÅ)
36- 40 F5.1 10-13m W(TiI)2N TiI(11949) NLTE equivalent width (mÅ)
42- 46 F5.1 10-13m W(FeI)1L FeI(11593) LTE equivalent width (mÅ)
48- 52 F5.1 10-13m W(FeI)1N FeI(11593) NLTE equivalent width (mÅ)
54- 59 F6.1 10-13m W(FeI)2L FeI(11638) LTE equivalent width (mÅ)
61- 66 F6.1 10-13m W(FeI)2N FeI(11638) NLTE equivalent width (mÅ)
68- 73 F6.1 10-13m W(FeI)3L FeI(11882) LTE equivalent width (mÅ)
75- 80 F6.1 10-13m W(FeI)3N FeI(11882) NLTE equivalent width (mÅ)
82- 87 F6.1 10-13m W(FeI)4L FeI(11973) LTE equivalent width (mÅ)
89- 94 F6.1 10-13m W(FeI)4N FeI(11973) NLTE equivalent width (mÅ)
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History:
* 21-Jan-2014: From electronic version of the journal
* 03-Mar-2014: fixed parameter [Z] in table2 and 3 for Te=4400K and 4000K
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 21-Jan-2014