2001A&A...376..232M


Query : 2001A&A...376..232M

2001A&A...376..232M - Astronomy and Astrophysics, volume 376, 232-247 (2001/9-2)

Heavy element abundances in cool dwarf stars: An implication for the evolution of the Galaxy.

MASHONKINA L. and GEHREN T.

Abstract (from CDS):

We present revised strontium, barium and europium abundances for 63 cool stars with metallicities [Fe/H] ranging from -2.20 to 0.25. The stellar sample has been extracted from Fuhrmann's lists (1998A&A...338..161F and 2001, in prep.). It is confined to main-sequence and turnoff stars. The results are based on NLTE line formation obtained in differential model atmosphere analyses of spectra that have a typical S/N of 200 and a resolution of 40000 to 60000. The element abundance ratios reveal a distinct chemical history of the halo and thick disk compared with that of the thin disk. Europium is overabundant relative to iron and barium in halo and thick disk stars suggesting that during the formation of these galactic populations high-mass stars exploding as SNe II dominated nucleosynthesis on a short time scale of the order of 1Gyr. We note the importance of [Eu/Mg] determinations for halo stars. Our analysis leads to the preliminary conclusion that Eu/Mg ratios found in halo stars do not support current theoretical models of the r-process based on low-mass SNe; instead they seem to point at a halo formation time much shorter than 1Gyr. A steep decline of [Eu/Fe] and a slight decline of [Eu/Ba] with increasing metallicity have been first obtained for thick disk stars. This indicates the start of nucleosynthesis in the lower mass stars, in SN I and AGB stars, which enriched the interstellar gas with iron and the most abundant s-process elements. From a decrease of the Eu/Ba ratio by ∼0.10 ... 0.15dex the time interval corresponding to the thick disk formation phase can be estimated. The step-like change of element abundance ratios at the thick to thin disk transition found in our previous analysis (Mashonkina & Gehren, 2000A&A...364..249M) is confirmed in this study: [Eu/Ba] and [Eu/Fe] are reduced by ∼0.25dex and ∼0.15dex, respectively; [Ba/Fe] increases by ∼0.1dex. This is indicative of an intermediate phase before the early stage of the thin disk developed, during which only evolved middle and low mass (<8M) stars contributed to nucleosynthesis. Our data provide an independent method to calculate the duration of this phase. The main s-process becomes dominant in the production of heavy elements beyond the iron group during the thin disk evolution. We find that in the thin disk stars Ba/Fe ratios increase with time from [Ba/Fe]=-0.06 in stars older than 8Gyr to [Ba/Fe]=0.06 in stars that are between 2 and 4Gyr old.

Abstract Copyright:

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

Simbad objects: 63

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Number of rows : 63
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 HD 3795 PM* 00 40 32.7939851012 -23 48 17.728718238   6.84 6.14     K0VFe-1.5CH-1.3 197 0
2 * eta Cas PM* 00 49 06.2945942922 +57 48 54.638239716 4.04 4.02 3.44 2.94 2.58 F9V 619 0
3 BPS CS 31082-0001 Pe* 01 29 31.1311443552 -16 00 45.495314460 12.527 12.427 11.642 11.189 10.713 CEMP 270 0
4 HD 10519 PM* 01 42 14.9182080778 -17 53 19.473849896   8.06 7.45     G2/3V 76 0
5 * 109 Psc PM* 01 44 55.8255136824 +20 04 59.336892804   6.984 6.279     G3Va 266 2
6 HD 18757 PM* 03 04 09.6346411530 +61 42 20.959769812   7.25   6.2   G1.5V 127 0
7 HE 0305-5442 Pe* 03 06 29.5014981984 -54 30 32.498486568   14.44 13.70 13.212 12.715 KIIvw 74 0
8 HD 19445 PM* 03 08 25.5883873084 +26 19 51.400965175 8.29 8.52 8.06 7.60 7.27 G2VFe-3 753 0
9 BD+66 268 PM* 03 31 17.4003449284 +66 43 49.024902152 10.48 10.57 9.91 9.30 8.87 G0 163 0
10 HD 22879 Pe* 03 40 22.0652879951 -03 13 01.124265616 7.146 7.222 6.667 6.346 6.016 G0VmF2 467 0
11 HD 30743 PM* 04 49 42.2441132544 -13 46 10.807837356   6.70 6.26     F6VFe-0.9CH-0.5 124 0
12 HD 30649 PM* 04 51 43.5748348116 +45 50 02.818509833 7.59 7.55 6.97 6.45 6.10 G2 221 0
13 HD 37124 PM* 05 37 02.4866159419 +20 43 50.832948117   8.35   7.2   G4IV-V 280 2
14 * 71 Ori PM* 06 14 50.8763445432 +19 09 23.212428948   5.64   4.9   F5.5IV-V 167 0
15 HD 45282 Pe* 06 26 40.7720940072 +03 25 29.792391024 8.71 8.69 8.03     Gwl 147 0
16 HD 52711 PM* 07 03 30.4592307736 +29 20 13.493121298 6.57 6.53   5.6   G0V 243 0
17 HD 55575 PM* 07 15 50.1391766472 +47 14 23.868404124 6.19 6.16   5.2   F9V 284 0
18 * 22 Lyn PM* 07 29 55.9571717856 +49 40 20.853841260   5.802 5.357     F6V 129 0
19 * alf CMi SB* 07 39 18.11950 +05 13 29.9552 0.82 0.79 0.37 -0.05 -0.28 F5IV-V+DQZ 1825 0
20 HD 62301 PM* 07 44 56.1929632534 +39 33 22.915760845 7.220 7.270   6.4   F8V 127 0
21 HD 64606 SB* 07 54 34.1880221064 -01 24 44.300470716 8.32 8.165 7.433 7.007 6.569 K0V 238 0
22 HD 65583 PM* 08 00 32.1297283166 +29 12 44.475101673 7.89 7.71 7.00 6.40 5.98 K0V_Fe-1.3 303 0
23 * mu.02 Cnc PM* 08 07 45.8562513552 +21 34 54.526814256 6.14 5.93 5.30     G1IVb 217 0
24 HD 68017 ** 08 11 38.6535558665 +32 27 25.787520185 7.63 7.50   6.4   G3V 154 0
25 BD+00 2245 PM* 08 16 57.7754525760 +00 01 03.593436636   10.36 9.76 9.55   G0 35 0
26 HD 69611 PM* 08 17 29.3481646355 -03 59 22.623439715   8.32 7.74     G0V 130 0
27 HD 84937 PM* 09 48 56.0992891997 +13 44 39.326709913 8.49 8.68 8.32 7.97 7.70 F8Vm-5 755 0
28 HD 90508 ** 10 28 03.88212 +48 47 05.6554 7.09 7.03   5.98   F9-V 234 1
29 HD 102158 PM* 11 45 30.5082432219 +47 40 00.768612834   8.66   7.7   G2 102 0
30 HD 103095 PM* 11 52 58.7673387755 +37 43 07.254113125 7.38 7.20 6.45 5.80 5.35 K1V_Fe-1.5 769 1
31 * bet CVn ** 12 33 44.5442516547 +41 21 26.921352859 4.91 4.86 4.25 3.73 3.42 G0V 562 0
32 HD 112758 SB* 12 59 01.5612841731 -09 50 02.679322421 8.737 8.384 7.588 7.163 6.729 G9V 174 1
33 * bet Com PM* 13 11 52.3938268062 +27 52 41.462309460 4.92 4.84 4.25 3.77 3.47 F9.5V 872 0
34 HD 115444 Pe* 13 16 42.4590842616 +36 22 52.692135420   9.77 8.97 8.3 7.88 G9V 233 0
35 * 70 Vir PM* 13 28 25.8085908881 +13 46 43.638308807 5.930 5.680 4.970 4.37 3.98 G4Va 696 1
36 HD 121560 PM* 13 55 49.9935853152 +14 03 23.407899444   6.66   5.9   F6V 131 0
37 BD+34 2476 PM* 13 59 09.4837849799 +33 51 39.379962282 10.25 10.44   9.7   sdF5 155 0
38 HD 126053 PM* 14 23 15.2847745835 +01 14 29.641269692 6.98 6.90 6.27 5.71 5.39 G1.5V 386 0
39 HD 130322 PM* 14 47 32.7262287384 -00 16 53.307811560   8.82 8.04     K0V 250 1
40 HD 132142 PM* 14 55 11.0437420721 +53 40 49.246687828 8.95 8.59 7.80 7.13 6.69 K1V 228 0
41 * 23 Lib PM* 15 13 28.6669233518 -25 18 33.653388418   7.168 6.46 6.43   G6IV-V 281 1
42 HD 140283 Pe* 15 43 03.0971190219 -10 56 00.595693188 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 893 0
43 * chi Her PM* 15 52 40.5410491705 +42 27 05.462878877 5.19 5.19 4.62 4.14 3.82 F8VFe-2Hdel-1 490 0
44 HD 144579 PM* 16 04 56.7936202756 +39 09 23.434584550 7.60 7.40 6.67 6.04 5.63 G8V 262 1
45 * w Her RG* 17 20 39.5674498400 +32 28 03.877958860 6.08 6.01 5.39 4.89 4.56 G0V 435 0
46 BD+02 3375 PM* 17 39 45.5948675731 +02 24 59.606824535 10.18 10.40 9.92 9.47 9.12 A5 191 0
47 HD 168009 PM* 18 15 32.4633956040 +45 12 33.540706764   6.931 6.298     G1V 200 0
48 HD 176377 PM* 18 58 51.0029782656 +30 10 50.318900724   7.37   6.4   G1V 114 0
49 HD 179957 PM* 19 12 04.6790033015 +49 51 13.997831536   7.25 6.59 6.2   G3V 117 0
50 HD 179958 PM* 19 12 05.0254435095 +49 51 20.695487091   7.12 6.47 6.1   G2V 131 0
51 HD 187923 PM* 19 52 03.4383778549 +11 37 41.972274281   6.78   5.8   G0V 196 0
52 * bet Aql PM* 19 55 18.7928429719 +06 24 24.351242346 5.040 4.560 3.710 3.05 2.56 G8IV 535 0
53 BPS CS 22885-0096 Pe* 20 20 51.1730095656 -39 53 30.234972840   14.02 13.33     CEMP-no 84 0
54 HD 194598 PM* 20 26 11.9183775668 +09 27 00.429558608 8.62 8.82 8.34 7.90 7.56 F8 293 0
55 HD 195019 PM* 20 28 18.6366815627 +18 46 10.180434472 7.730     6.5   G1V 242 1
56 * eta Cep PM* 20 45 17.3755540 +61 50 19.616737 4.960 4.320 3.410 2.76 2.27 K0IV 430 0
57 HD 201891 PM* 21 11 59.0321495469 +17 43 39.890919730 7.74 7.88 7.37 6.91 6.59 G5V_Fe-2.5 377 0
58 M 15 GlC 21 29 58.33 +12 10 01.2   3       ~ 3029 0
59 * 15 Peg PM* 21 52 29.9168018496 +28 47 36.750679764 5.82 5.95 5.53     F2V 233 0
60 HD 209458 V* 22 03 10.7727465312 +18 53 03.549393384   8.21 7.63     F9V 1051 1
61 BPS CS 22892-0052 Pe* 22 17 01.6558764360 -16 39 27.051026544   14.03 13.20 13.06 12.19 KIIvw 431 0
62 HE 2334-0604 Pe* 23 37 28.6873103640 -05 47 56.594641632   14.03 13.28 12.768 12.249 KIIvw 69 0
63 HD 222794 ** 23 43 27.0432915859 +58 04 49.071177861   7.77   6.8   G2V 77 0

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2022.08.10-07:50:14

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