J/A+A/324/435 Chemical composition of six K supergiants in the SMC (Hill 1997)
Chemical composition of six K supergiants in the Small Magellanic Cloud.
Hill V.
<Astron. Astrophys. 324, 435 (1997)>
=1997A&A...324..435H 1997A&A...324..435H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, supergiant ; Abundances
Keywords: stars: abundances - stars: supergiants - galaxies: Magellanic Clouds -
galaxies: abundances
Abstract:
A sample of six SMC cool stars (K supergiants) are analysed by high
resolution spectroscopy in order to investigate their chemical
content, which should reflect that of the current interstellar medium
within the SMC. The abundance of Na, Al, α-elements, Fe peak and
heavy elements are derived through an LTE analysis of the lines,
compared to a Galactic "standard" (the well-studied K giant Arcturus)
and discussed in terms of chemical evolution of the SMC. The following
results were obtained:
1. All the stars from this sample are metal deficient ([Fe/H] ranges
from -0.59 to -0.89dex). The abundance varies little from star-to-star
(0.10dex rms, comparable with the expected error due to uncertainties
on the effective parameters of the stars), in agreement with the very
small chemical composition variations among the H II regions within
the SMC found by Pagel et al. (1978MNRAS.184..569P 1978MNRAS.184..569P).
2. Sodium is not strongly enhanced in these stars, and the
star-to-star scatter is larger than expected.
3. At variance with metal-poor stars in our Galaxy, the so-called
α-elements do not seem to be enhanced.
4. Nickel displays a noticeable depletion with respect to iron
([Ni/Fe]≃-0.3dex), at variance with what is found in the SMC
F supergiants and in Arcturus.
5. Except for PMMR 144, the s and r process elements heavier than Ba
are enhanced in all of our stars by ≃+0.4dex.
Objects:
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RA (2000) DE Designation(s)
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00 48.8 -73 28 PMMR 23 = SkKM 36
00 49.2 -73 14 PMMR 27 = SkKM 43
00 51.9 -72 12 PMMR 48 = SkKM 79
00 59.8 -72 21 PMMR 102 = SkKM 191
01 03.3 -72 07 PMMR 144 = SkKM 250
01 03.3 -72 40 PMMR 145 = SkKM 248
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
appen 109 185 Lines used in the analysis
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Byte-by-byte Description of file: appen
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Bytes Format Units Label Explanations
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2- 8 F7.2 0.1nm Lambda Central wavelength of the line
10- 11 A2 --- Element Name of the element
12 I1 --- n_Element [1/2] Degree of ionization
1 for neutral, 2 for ionized species
14- 17 F4.2 eV Pext Excitation potential of the line
20- 24 F5.2 --- log(gf) ? Line transition probability in log scale
27- 31 F5.1 0.1pm EW23 ? Equivalent width of the line for star PMMR23
32 A1 --- n_EW23 [*] Note (1)
34- 38 F5.2 [Sun] [X/H]23 ? Abundance ([X/H]) for PMMR23
41- 45 F5.1 0.1pm EW27 ? Equivalent width of the line for star PMMR27
46 A1 --- n_EW27 [*] Note (1)
48- 52 F5.2 [Sun] [X/H]27 ? Abundance ([X/H]) for PMMR27
55- 59 F5.1 0.1pm EW48 ? Equivalent width of the line for star PMMR48
60 A1 --- n_EW48 [*] Note (1)
62- 66 F5.2 [Sun] [X/H]48 ? Abundance ([X/H]) for PMMR48
69- 73 F5.1 0.1pm EW102 ? Equivalent width of the line for star PMMR102
74 A1 --- n_EW102 [*] Note (1)
76- 80 F5.2 [Sun] [X/H]102 ? Abundance ([X/H]) for PMMR102
83- 87 F5.1 0.1pm EW144 ? Equivalent width of the line for star PMMR144
88 A1 --- n_EW144 [*] Note (1)
90- 94 F5.2 [Sun] [X/H]144 ? Abundance ([X/H]) for PMMR144
97-101 F5.1 0.1pm EW145 ? Equivalent width of the line for star PMMR145
102 A1 --- n_EW145 [*] Note (1)
104-108 F5.2 [Sun] [X/H]145 ? Abundance ([X/H]) for PMMR145
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Note (1): Asterisks means that the corresponding abundance was determined by
fitting the line profile rather than using this equivalent width,
due to a severe blend or to the hyperfine structure of the line.
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(End) Patricia Bauer [CDS] 27-Sep-1996