J/MNRAS/493/6095 SI abundances of 8 A-B stars (Mashonkina+, 2020)
Non-local thermodynamic equilibrium line formation for Si I-II-III in A-B stars
and the origin of Si II emission lines in ι Her.
Mashonkina L.
<Mon. Not. R. Astron. Soc., 493, 6095-6108 (2020)>
=2020MNRAS.493.6095M 2020MNRAS.493.6095M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, A-type ; Stars, B-type ; Abundances ; Optical
Keywords: line: formation - stars: abundances - stars: atmospheres
Abstract:
A comprehensive model atom was developed for Si I-II-III using the
most up-to-date atomic data available so far. Based on non-local
thermodynamic equilibrium (NLTE) line formation for Si I, Si II and Si
III and high-resolution observed spectra, we determined the NLTE
abundances for a sample of nine unevolved A9-B3 type stars with
well-determined atmospheric parameters. For each star, NLTE reduces
the line-to-line scatter for Si II substantially compared with the LTE
case and leads to consistent mean abundances from lines of different
ionization stages. In the hottest star of our sample, ι Her, Si
II is subject to overionization that drives emission in the lines
arising from the high-excitation doublet levels. Our NLTE calculations
reproduced 10 emission lines of Si II observed in ι Her. The same
overionization effect leads to greatly weakened Si II lines, which are
observed in absorption in ι Her. Large positive NLTE abundance
corrections (up to 0.98dex for 5055Å) were useful for achieving
consistent mean abundances from lines of the two ionization stages, Si
II and Si III. It was found that NLTE effects are overestimated for
the Si II 6347, 6371Å doublet in ι Her, while the new model
atom works well for cooler stars. At this stage, we failed to
understand this problem. We computed a grid of the NLTE abundance
corrections for lines of Si I, Si II and Si III in model atmospheres
with effective temperatures and surface gravities characteristic of
unevolved A-B type stars.
Description:
Atmospheric parameters of the sample stars and mean NLTE (N) and LTE
(L) abundances from lines of different ionization stages of silicon
for the A-B type stars sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 120 9 Atmospheric parameters of the sample stars and
mean NLTE and LTE abundances from lines of
different ionization stages of silicon
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Star name (HD NNNNNN)
11- 17 A7 --- OName Alternative name
19- 23 I5 K Teff Effective temperature
25- 28 F4.2 [cm/s2] logg Surface gravity
30- 34 F5.2 [-] [Fe/H] Fe/H abundance ratio
36- 38 F3.1 km/s vt Microturbulent velocity
40- 42 A3 --- Ref Reference for the star properties (1)
44- 45 I2 --- NlSiI ? Number of observed SiI lines
47- 50 F4.2 [-] logeSiIN ? Logarithm of the SiI NLTE abundance
52- 55 F4.2 [-] e_logeSiIN ? Error on logeSiIN
57- 60 F4.2 [-] logeSiIL ? Logarithm of the SiI LTE abundance
62- 65 F4.2 [-] e_logeSiIL ? Error on logeSiIL
67- 68 I2 --- NlSiII Number of observed SiII lines
70- 73 F4.2 [-] logeSiIIN Logarithm of the SiII NLTE abundance
75- 78 F4.2 [-] e_logeSiIIN Error on logeSiIIN
80- 83 F4.2 [-] logeSiIIL Logarithm of the SiII LTE abundance
85- 88 F4.2 [-] e_logeSiIIL Error on logeSiIIL
90 I1 --- flag [2]? Flag on Error on logeSiIIN and
logeSiIIL (2)
92 I1 --- NlSiIII ? Number of observed SiIII lines
94- 97 F4.2 [-] logeSiIIIN ? Logarithm of the SiIII NLTE abundance
99- 102 F4.2 [-] e_logeSiIIIN ? Error on logeSiIIIN
104- 107 F4.2 [-] logeSiIIIL ? Logarithm of the SiIII LTE abundance
109- 112 F4.2 [-] e_logeSiIIIL ? Error on logeSiIIIL
114- 118 F5.2 [-] [Si/H] Si/H abundance ratio
120 I1 --- f_[Si/H] [1/3]? Flag on [Si/H] (2)
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Note (1): Reference as follows:
C93 = Castelli & Kurucz (1993ASPC...44..496C 1993ASPC...44..496C)
F07 = Fossati et al. (2007A&A...476..911F 2007A&A...476..911F)
F09 = Fossati et al. (2009A&A...503..945F 2009A&A...503..945F, Cat. J/A+A/503/945)
F11 = Fossati et al. (2011MNRAS.417..495F 2011MNRAS.417..495F, Cat. J/MNRAS/417/495)
H93 = Hill & Landstreet (1993A&A...276..142H 1993A&A...276..142H, Cat. J/A+A/276/142)
N12 = Nieva & Przybilla (2012A&A...539A.143N 2012A&A...539A.143N, Cat. J/A+A/539/A143)
S16 = Sitnova, Mashonkina & Ryabchikova (2016MNRAS.461.1000S 2016MNRAS.461.1000S)
Note (2): Flag as follows:
1 = [Si/H] abundance based on SiII lines
2 = SiII 6347,6371Å and emission lines are not accounted for in the mean
3 = [Si/H] abundance based on SiIII lines
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 15-May-2023