2012A&A...540A..98M


Query : 2012A&A...540A..98M

2012A&A...540A..98M - Astronomy and Astrophysics, volume 540A, 98-98 (2012/4-1)

Non-LTE effects on the lead and thorium abundance determinations for cool stars.

MASHONKINA L., RYABTSEV A. and FREBEL A.

Abstract (from CDS):

Knowing accurate lead abundances of metal-poor stars provides constraints on the Pb production mechanisms in the early Galaxy. Accurately deriving thorium abundances permits a nucleo-chronometric age determination of the star. We aim to improve the calculation of the PbI and ThII lines in stellar atmospheres based on non-local thermodynamic equilibrium (non-LTE) line formation, and to evaluate the influence of departures from LTE on Pb and Th abundance determinations for a range of stellar parameters by varying the metallicity from the solar value down to [Fe/H]=-3. We present comprehensive model atoms for PbI and ThII and describe calculations of the PbI energy levels and oscillator strengths. The main non-LTE mechanism for PbI is the ultraviolet overionization. We find that non-LTE leads to systematically depleted total absorption in the PbI lines and accordingly, positive abundance corrections. The departures from LTE increase with decreasing metallicity. Using the semi-empirical model atmosphere HM74, we determine the lead non-LTE abundance for the Sun to be logεPb,☉=2.09, in agreement with the meteoritic lead abundance. We revised the Pb and Eu abundances of the two strongly r-process enhanced stars CS 31082-001 and HE 1523-0901 and the metal-poor stellar sample. Our new results provide strong evidence of universal Pb-to-Eu relative r-process yields during the course of Galactic evolution. The stars in the metallicity range -2.3<[Fe/H]←1.4 have Pb/Eu abundance ratios that are, on average, 0.51dex higher than those of strongly r-process enhanced stars. We conclude that the s-process production of lead started as early as the time when Galactic metallicity had reached [Fe/H]=-2.3. The average Pb/Eu abundance ratio of the mildly metal-poor stars, with -1.4≤[Fe/H]≤-0.59, is very close to the corresponding Solar System value, in line with the theoretical predictions that AGB stars with [Fe/H]≃-1 provided the largest contribution to the solar abundance of s-nuclei of lead. The departures from LTE for ThII are caused by the pumping transitions from the levels with Eexc<1eV. Non-LTE leads to weakened ThII lines and positive abundance corrections. Overall, the abundance correction does not exceed 0.2dex when collisions with HI atoms are taken into account in statistical equilibrium calculations.

Abstract Copyright:

Journal keyword(s): line: formation - nuclear reactions, nucleosynthesis, abundances - Sun: abundances - stars: abundances - stars: atmospheres

Simbad objects: 53

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Number of rows : 53
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 V* CM Cet LP? 00 33 14.3108581872 -10 43 42.728423844   10.66 9.48 8.84 9.06 G3/5V 99 0
2 HD 6755 SB* 01 09 43.0577179701 +61 32 50.264076956 8.48 8.40   7.3   G5 238 0
3 HD 6833 * 01 09 52.2648344184 +54 44 20.278107384 8.81 7.91 6.74     K0IIIbFe-2 194 0
4 HD 8724 RG* 01 26 17.5946147784 +17 07 35.123889432   9.29 8.34     G5 118 0
5 BD-16 251 RG* 01 29 31.1311443552 -16 00 45.495314460 12.527 12.427 11.642 11.189 10.713 CEMP 285 0
6 HD 20039 SB* 03 18 38.5002297504 +72 16 30.442783335       8.4   G6 61 0
7 HD 23798 Pe* 03 46 45.7220393712 -30 51 13.333194972   9.35 8.32     G8/K1(III)wF0/3 70 0
8 HD 23439A EB* 03 47 02.1135215373 +41 25 38.103867665   8.89 8.12 7.7   K2:V_Fe-1.3 238 0
9 HD 26297 Pe* 04 09 03.4178692512 -15 53 27.056905800   8.55 7.47 7.09   G5/6IVw 155 0
10 HD 29907 SB* 04 38 22.3989572020 -65 24 57.594232229   10.52 9.91     F8V 98 0
11 V* HP Eri LP* 04 38 55.7330378304 -13 20 48.133934448 10.91 9.72 8.33     G8/K0IIIwF7 132 0
12 HD 246132 SB* 05 40 09.7460841768 +12 10 41.058951312       9.8   G5 71 0
13 HD 37828 Pe* 05 40 54.6448450584 -11 12 00.189470088   7.988 6.869     G8III 99 0
14 HD 247297 PM* 05 45 40.3823732400 +14 41 20.113355472       8.7   G0 40 0
15 HD 250792 Pe* 06 03 14.8636143602 +19 21 38.696218609 9.89 9.898 9.310 8.954 8.547 G1 163 0
16 HD 44007 Pe* 06 18 48.5269024752 -14 50 43.423248948   8.85 8.06 7.69   G5(IV)wF3/5 183 0
17 HD 63791 PM* 07 54 28.7247271128 +62 08 10.773103272   8.81 7.90     G0 112 0
18 BD+00 2245 PM* 08 16 57.7754525760 +00 01 03.593436636   10.36 9.76 9.55   G0 35 0
19 HD 74462 RG* 08 48 20.6518818744 +67 26 59.884515744   9.65 8.69 8.25   G5IV 131 0
20 G 47-12 PM* 08 57 59.2546963872 +24 28 22.529303813   12.52   11.9   ~ 44 0
21 HD 94028 PM* 10 51 28.1256073369 +20 16 38.965439278 8.51 8.69 8.22 7.82 7.54 F8 356 0
22 HD 103095 Pe* 11 52 58.7673387755 +37 43 07.254113125 7.38 7.20 6.45 5.80 5.35 K1V_Fe-1.5 792 1
23 BD+22 2442 ** 12 08 54.6643937369 +21 47 19.441164053       9.0   G2V 63 1
24 HD 105755 PM* 12 10 15.8753498232 +54 29 17.311799904   9.14 8.59     G0Vw 79 0
25 HD 105861 Pe* 12 10 55.3590882038 +44 00 11.823912855       9.9   G5 26 0
26 HD 106516 SB* 12 15 10.55731 -10 18 44.6354 6.44 6.57 6.11     F9VFe-1.7CH-0.7 416 0
27 HD 108317 Pe* 12 26 36.8319587208 +05 18 09.023783400       7.7   G2IVm-5 164 0
28 BD+29 2356 RG* 13 01 52.4291777760 +29 11 17.936259972   12.27 11.50     ~ 25 0
29 HD 121135 Pe* 13 53 33.5447403552 +02 41 41.185079880   10.14 9.37     KIIvw 65 0
30 HD 122956 Pe* 14 05 13.0244442888 -14 51 25.455804480   8.18 7.3 6.88   G6IV/VwF6 155 0
31 BD+01 2916 Pe* 14 21 45.2614710696 +00 46 59.173056516   10.93 9.65     KIIvw 91 0
32 BD+30 2611 Pe* 15 06 53.8282684752 +30 00 36.941373756 11.50 10.37 9.13     G8III 139 0
33 BD+33 2560 PM* 15 14 26.1845599776 +33 00 38.275996248   11.5   10.1   G3 35 1
34 HE 1523-0901 Pe* 15 26 01.0697532504 -09 11 38.885639784   12.37 11.50 10.476 9.863 CEMP 77 0
35 HD 140283 Pe* 15 43 03.0971190219 -10 56 00.595693188 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 926 0
36 HD 141531 PM* 15 49 16.4993243976 +09 36 42.408069804   10.31 9.08 8.720   M1V 69 0
37 HD 166161 PM* 18 09 40.6841536776 -08 46 45.603012144 9.53 9.13 8.16     G0wF0 140 0
38 BD+05 3640 PM* 18 12 21.8774787073 +05 24 04.408187063   11.16   9.9   G8 85 0
39 HD 171496 * 18 36 07.4934525456 -24 26 11.309788572   9.59 8.52     G8IV 75 1
40 HD 175305 RG* 18 47 06.4416868934 +74 43 31.451436187 8.07 7.93 7.18 6.52 6.03 G5III 217 0
41 HD 187111 Pe* 19 48 39.5744746680 -12 07 19.738101036   8.92 7.75     G8wF8III/IV 140 0
42 HD 201891 Pe* 21 11 59.0321495469 +17 43 39.890919730 7.74 7.88 7.37 6.91 6.59 G5V_Fe-2.5 391 0
43 HD 204543 * 21 29 28.2126852216 -03 30 55.353564216   9.17 8.30 7.99   F6/8(V) 135 0
44 HD 206739 PM* 21 44 23.9461069656 -11 46 22.843385220   9.45 8.60 8.14   G5V 79 0
45 BD+19 4788 PM* 21 48 19.2876425352 +19 58 30.634725936       9.6   ~ 36 0
46 HD 210295 Pe* 22 09 41.4458512176 -13 36 19.475979192   10.49 10.10     Gwl 91 0
47 HD 235766 PM* 22 14 47.1706275528 +50 47 15.413299080   10.03 9.01     G5 12 0
48 HD 214925 LP? 22 41 59.4323837856 -20 47 03.709481964   10.77 9.30     (F) 36 0
49 BD-00 4470 Pe* 23 09 32.9443500338 +00 42 39.749975827   10.66   9.6   sdG2 95 2
50 BD+20 5292 PM* 23 13 17.1485820576 +20 56 33.928500696       9.4   G5 27 0
51 G 29-25 PM* 23 22 18.1564550808 +12 09 33.607015452   11.48   10.6   G8: 34 0
52 HD 220838 * 23 27 16.4821789104 -26 58 58.175202936   10.50 9.39     G6/8(III)w 57 0
53 HD 221170 Pe* 23 29 28.8087143040 +30 25 57.849303180 9.43 8.74 7.66     CEMP-r 284 0

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2023.11.30-11:46:12

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