2000A&A...364..249M


C.D.S. - SIMBAD4 rel 1.7 - 2019.11.13CET07:05:16

2000A&A...364..249M - Astronomy and Astrophysics, volume 364, 249-264 (2000/12-1)

Barium and europium abundances in cool dwarf stars and nucleosynthesis of heavy elements.

MASHONKINA L. and GEHREN T.

Abstract (from CDS):

We revise barium abundances in 29 cool stars with metallicities [Fe/H] ranging from -2.20 to 0.07 and europium abundances in 15 stars with [Fe/H] from -1.52 to 0.07. The sample has been extracted from Fuhrmann's lists (1998A&A...338..161F, 2001, submitted to A&A) and confined to main-sequence and turnoff stars with only one subgiant added. The results are based on differential NLTE model atmosphere analyses of spectra that have a typical S/N of 200 and a resolution of 40000 or 60000. The statistical equilibrium of EuII is first investigated with a model atom containing 32 levels of EuII plus the ground state of EuIII. NLTE effects decrease the equivalent widths of the EuII lines compared with LTE resulting in positive NLTE abundance corrections which are below 0.08dex for all the stars investigated. The solar barium abundance logεBa,☉=2.21 and the europium abundance logεEu,☉=0.53 are found from the BaII and EuII solar flux line profile fitting, and they coincide within error bars with meteoritic abundances of Grevesse et al. (1996, ASP Conf. Ser. 99, 117). Here the usual scale with logεH=12 is used. The isotopic ratio 151Eu:153Eu=55:45 is obtained from solar disk center intensity profile fitting of the EuII λ4129Å line. We report here for the first time that the elemental ratios [Ba/Fe], [Eu/Fe] and [Eu/Ba] show a different behaviour for stars of different Galactic populations. For the halo stars the [Ba/Fe] ratios are approximately solar, europium is overabundant relative to iron and barium with the mean values [Eu/Fe]=0.62 and [Eu/Ba]=0.64. For thick disk stars it is found that a) barium is slightly underabundant relative to iron by about 0.1dex; b) europium is overabundant relative to iron with the [Eu/Fe] ratios between 0.30 and 0.44; and c) europium is overabundant relative to barium with a mean value of [Eu/Ba]=0.49±0.03. A step-like change in the [Eu/Ba] and [Ba/Fe] ratios occurs at the thick to thin disk transition; so, nearly solar elemental ratios [Ba/Fe], [Eu/Fe] and [Eu/Ba] are found for the thin disk stars. These data suggest that a) the halo and thick disk stellar population formed quickly during an interval comparable with the evolution time of an AGB progenitor of 3 to 4 M, and the r-process dominated heavy element production at that epoch; b) there was a hiatus in star formation before the early stage of the thin disk developed. The even-to-odd Ba isotope ratios estimated from hyperfine structure (HFS) affecting the BaII resonance line in the halo and thick disk stars favour a significant contribution of 138Ba to barium for a pure r-process, and this is supported by the recent data of Arlandini et al. (1999ApJ...525..886A).

Abstract Copyright:

Journal keyword(s): line: formation - nuclear reactions, nucleosynthesis, abundances - Sun: abundances - stars: abundances - stars: late-type - Galaxy: evolution

Simbad objects: 31

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Number of rows : 31

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 HD 400 PM* 00 08 40.9385088178 +36 37 37.648934145       5.9   F8IV 150 0
2 * mu. Cas SB* 01 08 16.39470 +54 55 13.2264 5.93 5.86 5.17 4.55 4.13 G5Vb 537 1
3 HD 9407 PM* 01 34 33.2643888977 +68 56 53.288116227   7.21   6.1   G6.5V 129 0
4 BD+29 366 PM* 02 10 24.5274383291 +29 48 23.663384860 9.27 9.35 8.77 8.24 7.85 G3 119 0
5 HD 19445 PM* 03 08 25.5884 +26 19 51.400 8.29 8.52 8.06 7.60 7.27 G2VFe-3 733 0
6 BD+66 268 PM* 03 31 17.4003372547 +66 43 49.024023927 10.48 10.57 9.91 9.30 8.87 G0 156 0
7 HD 22879 Pe* 03 40 22.0654223510 -03 13 01.124769689 7.146 7.222 6.667 6.346 6.016 G0VmF2 422 0
8 HD 30649 PM* 04 51 43.5714471304 +45 50 02.842355226 7.59 7.55 6.97 6.45 6.10 G2 211 0
9 * 71 Ori PM* 06 14 50.8755168504 +19 09 23.210642162   5.64   4.9   F5.5IV-V 155 0
10 HD 45282 Pe* 06 26 40.7720108507 +03 25 29.794070200 8.71 8.69 8.03     Gwl 138 0
11 HD 52711 PM* 07 03 30.4588797095 +29 20 13.496987787 6.57 6.53   5.6   G0V 221 0
12 * alf CMi SB* 07 39 18.11950 +05 13 29.9552 0.82 0.79 0.37 -0.05 -0.28 F5IV-V+DQZ 1742 0
13 HD 62301 PM* 07 44 56.1933366656 +39 33 22.916336799 7.220 7.270   6.4   F8V 117 0
14 HD 69611 PM* 08 17 29.3479423950 -03 59 22.619129726   8.32 7.74     G0V 115 0
15 HD 84937 PM* 09 48 56.09801 +13 44 39.3237 8.49 8.68 8.32 7.97 7.70 F8Vm-5 708 0
16 HD 102158 PM* 11 45 30.5085093403 +47 40 00.770718104   8.66   7.7   G2 91 0
17 HD 103095 PM* 11 52 58.7683801554 +37 43 07.240082865 7.38 7.20 6.45 5.80 5.35 K1V_Fe-1.5 734 1
18 HD 114762 SB* 13 12 19.7467346230 +17 31 01.611425890 7.78         F9VgF8mF4+M6?V 499 1
19 * 70 Vir PM* 13 28 25.8081883620 +13 46 43.642951116 5.930 5.680 4.970 4.37 3.98 G4Va 662 1
20 BD+34 2476 PM* 13 59 09.4838035693 +33 51 39.380333439 10.25 10.44   9.7   sdF5 147 0
21 HD 140283 Pe* 15 43 03.0967798658 -10 56 00.595803430 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 845 0
22 * w Her PM* 17 20 39.5675395123 +32 28 03.877348066 6.08 6.01 5.39 4.89 4.56 G0V 413 0
23 BD+02 3375 PM* 17 39 45.5950264172 +02 24 59.607595293 10.18 10.40 9.92 9.47 9.12 A5 180 0
24 HD 184499 PM* 19 33 27.0811098549 +33 12 06.717932615 7.22 7.22 6.64 6.14 5.79 G0V 223 0
25 * 16 Cyg A ** 19 41 48.9539315338 +50 31 30.218780803 6.79 6.59 5.95 5.50 5.17 G1.5Vb 665 1
26 * omi Aql PM* 19 51 01.6437560393 +10 24 56.595177367   5.66   4.8   F8V 414 0
27 HD 194598 PM* 20 26 11.9185966774 +09 27 00.429262518 8.62 8.82 8.34 7.90 7.56 F8 282 0
28 HD 201891 PM* 21 11 59.0322335571 +17 43 39.888647667 7.74 7.88 7.37 6.91 6.59 G5V_Fe-2.5 365 0
29 HD 204155 PM* 21 26 42.9051661431 +05 26 29.899070605   9.03   8.1   F7V 113 0
30 BPS CS 22892-0052 Pe* 22 17 01.6558480594 -16 39 27.051900047   14.03 13.20 13.06 12.19 KIIvw 400 0
31 HD 221830 PM* 23 35 28.8946565621 +31 01 01.832810749   7.45   6.5   G2 140 0

    Equat.    Gal    SGal    Ecl

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2019.11.13-07:05:16

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