2013A&A...551A..57H


C.D.S. - SIMBAD4 rel 1.7 - 2020.03.28CET22:33:20

2013A&A...551A..57H - Astronomy and Astrophysics, volume 551A, 57-57 (2013/3-1)

LTE or non-LTE, that is the question. The NLTE chemical evolution of strontium in extremely metal-poor stars.

HANSEN C.J., BERGEMANN M., CESCUTTI G., FRANCOIS P., ARCONES A., KARAKAS A.I., LIND K. and CHIAPPINI C.

Abstract (from CDS):

Strontium has proven itself to be one of the most important neutron-capture elements in the study of metal-poor stars. Thanks to the strong absorption lines of Sr, they can be detected even in the most metal-poor stars and also in low-resolution spectra. However, we still cannot explain the large star-to-star abundance scatter we derive for metal-poor stars. Here we compare Galactic chemical evolution (GCE) predictions with improved abundances for SrI and SrII, including updated atomic data, to evaluate possible explanations for the large star-to-star scatter at low metallicities. We have derived abundances under both local thermodynamic equilibrium (LTE) and non-LTE (NLTE) for stars spanning a large interval of metallicities, as well as a broad range of other stellar parameters. Gravities and metallicities are also determined in NLTE. We employed MARCS stellar atmospheres and MOOG for the LTE spectrum synthesis, while MAFAGS and DETAIL were used to derive the NLTE abundances. We verified the consistency of the two methods in LTE. We confirm that the ionisation equilibrium between SrI and SrII is satisfied under NLTE but not LTE, where the difference between neutral and ionised Sr is on average ∼0.3dex. We show that the NLTE corrections are of increasing importance as the metallicity decreases. For the stars with [Fe/H]>-3, the SrI NLTE correction is ∼0.35/0.55dex in dwarfs/giants, while the SrII NLTE correction is <±0.05dex. On the basis of the large NLTE corrections to SrI, SrI should not be applied as a chemical tracer under LTE, while it is a good tracer under NLTE. SrII, on the other hand, is a good tracer under both LTE and NLTE (down to [Fe/H]~-3), and LTE is a safe assumption for this majority species (if the NLTE corrections are not available). However, the Sr abundance from SrII lines depends on determining an accurate surface gravity, which can be obtained from the NLTE spectroscopy of Fe lines or from parallax measurements. We could not explain the star-to-star scatter (which remains under both LTE and NLTE) by the use of the Galactic chemical evolution model, since Sr yields to date have been too uncertain to draw firm conclusions. At least two nucleosynthetic production sites seem necessary to account for this large scatter.

Abstract Copyright:

Journal keyword(s): stars: abundances - Galaxy: evolution

Status at CDS:  

Simbad objects: 73

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Number of rows : 73

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 BPS BS 17570-0063 Pe* 00 20 36.1934507252 +23 47 37.625665043   14.84 14.51     ~ 23 0
2 BPS CS 29527-0015 Pe* 00 29 10.6813715074 -19 10 07.306464364   14.61 14.24     CEMP-no 51 0
3 HE 0027-3613 Pe* 00 30 15.9613306172 -35 56 51.230873749     14.74     ~ 27 0
4 HD 2796 Pe* 00 31 16.9149599675 -16 47 40.792690842 9.58 9.28 8.50 8.14 8.67 Fw 177 0
5 HD 3567 PM* 00 38 31.9476246205 -08 18 33.395481958 9.54 9.70 9.23     F7/8wF3 189 0
6 CD-38 245 Pe* 00 46 36.1954714218 -37 39 33.555736375   12.733 11.929 13.39 10.996 KIIvw 200 0
7 BPS CS 22953-0003 Pe* 01 02 15.8722809261 -61 43 45.836705614   14.43 13.75 13.339 12.886 KIIvw 53 0
8 BPS CS 29518-0020 * 01 12 13.2161077183 -31 00 05.359705182 14.164 14.41 14.00     ~ 18 0
9 BPS CS 29518-0043 * 01 18 38.3021781706 -30 41 02.851142792 14.730 14.94 14.57     ~ 23 0
10 BPS CS 29518-0051 Pe* 01 24 10.0046408484 -28 15 21.119402152 13.567 13.62 13.02 12.594 12.162 ~ 30 0
11 BPS CS 22953-0037 Pe* 01 25 06.6511385034 -59 16 00.741420364   14.01 13.64   13.13 CEMP-no 39 0
12 BPS CS 31082-0001 Pe* 01 29 31.1311330115 -16 00 45.496485322 12.527 12.427 11.642 11.189 10.713 CEMP 239 0
13 BPS CS 31061-0032 Pe* 02 38 43.3010009273 +03 19 02.564348687   14.30 13.90 13.581 13.290 ~ 25 0
14 HE 0239-1340 Pe* 02 41 42.3721693746 -13 28 10.604872550   14.73 13.97 13.566 13.080 CEMP-no 53 0
15 HE 0305-5442 Pe* 03 06 29.5014936276 -54 30 32.498352902   14.44 13.70 13.212 12.715 KIIvw 72 0
16 HD 19445 PM* 03 08 25.5884 +26 19 51.400 8.29 8.52 8.06 7.60 7.27 G2VFe-3 735 0
17 HE 0311-1046 Pe* 03 14 20.8495240680 -10 35 11.279671787   13.54 12.73 12.204 11.693 KIIvw 64 0
18 HE 0315+0000 Pe* 03 17 39.0098946532 +00 11 04.598852939     15.516   14.506 ~ 10 0
19 BPS CS 22177-0009 Pe* 04 07 40.6490023717 -25 02 43.969982222   14.67 14.27     ~ 29 0
20 HE 0409-1212 Pe* 04 12 13.8814170981 -12 05 05.075798490   13.843 12.897   11.764 ~ 59 0
21 BPS CS 22186-0025 Pe* 04 24 32.7982638728 -37 09 02.518352449   14.99 14.24 13.740 13.269 ~ 33 0
22 HD 74462 PM* 08 48 20.6518837664 +67 26 59.887115014   9.65 8.69 8.25   G5IV 120 0
23 BD-13 3442 Pe* 11 46 50.6526364381 -14 06 43.453858029   10.662 10.274     CEMP 89 0
24 HD 106038 PM* 12 12 01.3690548564 +13 15 40.620671155 10.45 10.630 10.162 9.851 9.539 F6wl 167 0
25 HE 1219-0312 Pe* 12 21 34.1430157283 -03 28 39.635608057     15.940   15.043 ~ 30 0
26 BPS BS 16076-0006 Pe* 12 48 22.7519780017 +20 56 44.030641966   13.88 13.36 13.115 12.706 ~ 19 0
27 Wolf 1492 Pe* 13 40 02.4921790616 -00 02 18.750321114 11.601 11.832 11.451 11.184 10.892 sdF0: 259 0
28 BPS BS 16467-0062 Pe* 13 42 00.6325668250 +17 48 40.825137829   14.69 14.09 13.665 13.216 ~ 45 0
29 HD 121004 PM* 13 53 58.1163515488 -46 32 19.526169178   10.112 9.522     G2V 124 0
30 BPS BS 16554-0041 Pe* 14 00 54.4741225648 +22 46 42.087338110 14.317 14.548 14.230     ~ 21 0
31 HD 122196 PM* 14 01 02.1244272306 -38 03 03.297565043   9.19 8.75     F0(V)w 106 0
32 Ross 841 Pe* 14 02 30.0901582051 -05 39 05.181328144   11.508 11.149 10.866 10.576 sdA3 136 0
33 HD 122563 Pe* 14 02 31.8456299772 +09 41 09.942736952 7.47 7.10 6.19 5.37 4.79 G8:III:Fe-5 735 0
34 HD 126238 Pe* 14 25 29.9570911985 -43 38 36.947126248   8.44 7.68 7.44   G3/8wF0/2 101 1
35 HD 126587 Pe* 14 27 00.3636840211 -22 14 38.991614082   9.88 9.60 8.75   CEMP-no 121 0
36 BPS BS 16477-0003 Pe* 14 32 56.9230863125 +06 46 06.975505394   14.94 14.22 13.727 13.224 ~ 34 0
37 BPS CS 30325-0094 Pe* 14 54 39.2685324873 +04 21 38.098655567   13.02 12.32 11.849 11.376 ~ 43 0
38 BPS BS 16968-0061 Pe* 15 01 06.1170779628 +03 42 45.573988083   13.73 13.22 13.39   ~ 28 0
39 HD 134169 SB* 15 08 18.0562462154 +03 55 50.107808860 8.14 8.22 7.70     F7V 195 0
40 UCAC2 31517587 Pe* 15 08 29.6580275604 -00 35 59.273543748   13.37 12.95   12.37 ~ 25 0
41 BPS CS 30312-0059 Pe* 15 34 48.8386734596 -01 23 37.343657126   13.85 13.14 12.596 12.065 ~ 22 0
42 HD 140283 Pe* 15 43 03.0967798658 -10 56 00.595803430 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 848 0
43 HD 142038 * 15 52 09.7806744123 +04 38 05.056618320   10.24 9.24     K0IV 4 0
44 HD 148816 PM* 16 30 28.4586643435 +04 10 41.603810207 7.75 7.81 7.28 6.82 6.49 F7V 280 0
45 BPS CS 22878-0101 Pe* 16 45 31.4514010341 +08 14 45.471045094   14.59 13.79   12.673 KIIvw 55 0
46 BD+17 3248 HB* 17 28 14.4691668039 +17 30 35.848406966   10.02 9.34     KIIvw 196 0
47 HD 175305 Pe* 18 47 06.4424234462 +74 43 31.448124921 8.07 7.93 7.18 6.52 6.03 G5III 190 0
48 HD 184448 PM* 19 32 02.5281551739 +50 10 53.559251885   8.69   7.7   F8 54 0
49 BPS CS 22891-0209 Pe* 19 42 02.1800028329 -61 03 44.536144090   13.03 12.18     KIIvw 53 0
50 UCAC2 7177623 Pe* 19 42 26.8930018981 -56 58 34.061929902   14.27 13.63     ~ 45 0
51 HD 186478 Pe* 19 45 14.1410795461 -17 29 27.071420634   10.116 9.302 8.527 7.961 K2III 128 0
52 UCAC2 5726991 Pe* 19 53 49.7800945675 -59 40 00.163969151   13.592 12.620   11.48 KIIvw 42 0
53 BD-18 5550 Pe* 19 58 49.7370363913 -18 12 11.142309703 10.18 10.03 9.35 9.04 8.74 CEMP-no 161 0
54 BPS CS 22873-0166 Pe* 20 19 22.0361305437 -61 30 15.121053020   12.818 11.802 11.52 10.57 KIIvw 46 0
55 BPS CS 22885-0096 Pe* 20 20 51.1729562140 -39 53 30.235406812   14.02 13.33     CEMP-no 81 0
56 BPS CS 22897-0008 Pe* 21 03 11.8563237064 -65 05 08.852932036   14.02 13.33     CEMP-no 62 0
57 BPS CS 29506-0007 Pe* 21 20 28.6541606696 -20 46 22.955747614     14.18     ~ 28 0
58 BPS CS 29506-0090 Pe* 21 30 28.8706794433 -22 10 41.578963371     14.33     ~ 26 0
59 BPS CS 29495-0041 Pe* 21 36 33.2901533828 -28 18 48.439267198 14.111 14.15 13.34   12.222 ~ 30 0
60 HE 2141-3741 Pe* 21 44 51.1647173336 -37 27 55.017357431   14.10 13.47     CEMP-no 51 0
61 BPS CS 22948-0093 Pe* 21 50 31.5179802313 -41 07 49.353957554   15.54 15.18     ~ 32 0
62 BPS CS 22956-0050 Pe* 21 58 05.8339798575 -65 13 27.160917994   14.95 14.25 13.745 13.211 CEMP-no 35 0
63 BPS BS 17569-0049 Pe* 22 04 58.3605638072 +04 01 32.135813469 14.503 14.25 13.36 12.805 12.259 ~ 27 0
64 BPS CS 22965-0054 Pe* 22 06 30.2933577439 -02 32 34.433172529   15.69 15.07 14.732 14.072 CEMP-no 33 0
65 BPS CS 22892-0052 Pe* 22 17 01.6558480594 -16 39 27.051900047   14.03 13.20 13.06 12.19 KIIvw 405 0
66 BPS CS 29516-0041 Pe* 22 21 48.8261125099 +02 28 44.864481048 13.291 13.4 12.74 12.325 12.013 ~ 35 0
67 BPS CS 29516-0024 Pe* 22 26 15.3575399312 +02 51 46.325239449   14.43 13.57 13.011 12.416 ~ 32 0
68 BPS CS 29491-0053 Pe* 22 36 56.2964405478 -28 31 06.577841168   13.76 12.92 12.380 11.812 ~ 31 0
69 BPS CS 22888-0031 Pe* 23 11 32.4788632961 -35 26 42.874207261   15.31 14.90     CEMP-no 32 0
70 BPS CS 22966-0011 Pe* 23 35 07.0484328903 -30 22 54.279012782 14.694 14.97 14.55     ~ 25 0
71 HE 2334-0604 Pe* 23 37 28.6873335486 -05 47 56.594686365   14.03 13.28 12.768 12.249 KIIvw 67 0
72 BPS CS 22966-0057 Pe* 23 48 57.7535714010 -29 39 22.828517864 14.759   14.32   13.512 ~ 31 0
73 SB 966 Pe* 23 53 40.2977653893 -26 58 43.988331934   13.50 13.050     sdF/G? 34 0

    Equat.    Gal    SGal    Ecl

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2020.03.28-22:33:20

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