2007A&A...464.1081A


C.D.S. - SIMBAD4 rel 1.7 - 2019.09.19CEST23:47:51

2007A&A...464.1081A - Astronomy and Astrophysics, volume 464, 1081-1087 (2007/3-4)

NLTE determination of the sodium abundance in a homogeneous sample of extremely metal-poor stars.

ANDRIEVSKY S.M., SPITE M., KOROTIN S.A., SPITE F., BONIFACIO P., CAYREL R., HILL V. and FRANCOIS P.

Abstract (from CDS):

Abundance ratios in extremely metal-poor (EMP) stars are a good indication of the chemical composition of the gas in the earliest phases of the Galaxy evolution. It had been found from an LTE analysis that at low metallicity, and in contrast with most of the other elements, the scatter of [Na/Fe] versus [Fe/H] was surprisingly large and that, in giants, [Na/Fe] decreased with metallicity. Since it is well-known that the formation of sodium lines is very sensitive to non-LTE effects, to firmly establish the behaviour of the sodium abundance in the early Galaxy, we have used high quality observations of a sample of EMP stars obtained with UVES at the VLT, and we have taken into account the non-LTE line formation of sodium. The profiles of the two resonant sodium D lines (only these sodium lines are detectable in the spectra of EMP stars) have been computed in a sample of 54 EMP giants and turn-off stars (33 of them with [Fe/H]←3.0) with a modified version of the code MULTI, and compared to the observed spectra. With these new determinations in the range -4<[Fe/H]←2.5, both [Na/Fe] and [Na/Mg] are almost constant with a low scatter. In the turn-off stars and ``unmixed'' giants (located in the low RGB): [Na/Fe]=-0.21±0.13 or [Na/Mg]=-0.45±0.16. These values are in good agreement with the recent determinations of [Na/Fe] and [Na/Mg] in nearby metal-poor stars. Moreover we confirm that all the sodium-rich stars are ``mixed'' stars (i.e., giants located after the bump, which have undergone an extra mixing). None of the turn-off stars is sodium-rich. As a consequence it is probable that the sodium enhancement observed in some mixed giants is the result of a deep mixing.

Abstract Copyright:

Journal keyword(s): line: formation - line: profiles - stars: abundances - convection - stars: supernovae: general - Galaxy: evolution

Simbad objects: 55

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Number of rows : 55

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#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 50 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 176 0
5 CD-38 245 Pe* 00 46 36.1954714218 -37 39 33.555736375   12.733 11.929 13.39 10.996 KIIvw 199 0
6 BPS CS 22953-0003 Pe* 01 02 15.8722809261 -61 43 45.836705614   14.43 13.75 13.339 12.886 KIIvw 52 0
7 BPS CS 29518-0020 * 01 12 13.2161077183 -31 00 05.359705182 14.164 14.41 14.00     ~ 18 0
8 BPS CS 29518-0043 * 01 18 38.3021781706 -30 41 02.851142792 14.730 14.94 14.57     ~ 23 0
9 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
10 BPS CS 22953-0037 Pe* 01 25 06.6511385034 -59 16 00.741420364   14.01 13.64   13.13 CEMP-no 38 0
11 BPS CS 31082-0001 Pe* 01 29 31.1311330115 -16 00 45.496485322 12.527 12.427 11.642 11.189 10.713 ~ 237 0
12 BPS CS 29528-0041 Pe* 02 29 25.2507036195 -18 13 28.042501354 14.83 15.20 14.59 14.67   CEMP-no 23 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 52 0
15 HE 0305-5442 Pe* 03 06 29.5014936276 -54 30 32.498352902   14.44 13.70 13.212 12.715 KIIvw 70 0
16 HE 0311-1046 Pe* 03 14 20.8495240680 -10 35 11.279671787   13.54 12.73 12.204 11.693 KIIvw 62 0
17 BPS CS 22177-0009 Pe* 04 07 40.6490023717 -25 02 43.969982222   14.67 14.27     ~ 29 0
18 HE 0409-1212 Pe* 04 12 13.8814170981 -12 05 05.075798490   13.843 12.897   11.764 ~ 57 0
19 BPS CS 22186-0025 Pe* 04 24 32.7982638728 -37 09 02.518352449   14.99 14.24 13.740 13.269 ~ 33 0
20 Wolf 1492 Pe* 13 40 02.4921790616 -00 02 18.750321114 11.601 11.832 11.451 11.184 10.892 sdF0: 255 0
21 BPS BS 16467-0062 Pe* 13 42 00.6325668250 +17 48 40.825137829   14.69 14.09 13.665 13.216 ~ 44 0
22 BPS BS 16554-0041 Pe* 14 00 54.4741225648 +22 46 42.087338110 14.317 14.548 14.230     ~ 21 0
23 HD 122563 Pe* 14 02 31.8456299772 +09 41 09.942736952 7.47 7.10 6.19 5.37 4.79 G8:III:Fe-5 722 0
24 BPS BS 16477-0003 Pe* 14 32 56.9230863125 +06 46 06.975505394   14.94 14.22 13.727 13.224 ~ 33 0
25 BPS CS 30325-0094 Pe* 14 54 39.2685324873 +04 21 38.098655567   13.02 12.32 11.849 11.376 ~ 42 0
26 BPS BS 16968-0061 Pe* 15 01 06.1170779628 +03 42 45.573988083   13.73 13.22 13.39   ~ 27 0
27 UCAC2 31517587 Pe* 15 08 29.6580275604 -00 35 59.273543748   13.37 12.95   12.37 ~ 25 0
28 BPS CS 22878-0101 Pe* 16 45 31.4514010341 +08 14 45.471045094   14.59 13.79   12.673 KIIvw 54 0
29 BD+17 3248 HB* 17 28 14.4691668039 +17 30 35.848406966   10.02 9.34     KIIvw 195 0
30 BPS CS 22891-0209 Pe* 19 42 02.1800028329 -61 03 44.536144090   13.03 12.18     KIIvw 52 0
31 UCAC2 7177623 Pe* 19 42 26.8930018981 -56 58 34.061929902   14.27 13.63     ~ 45 0
32 HD 186478 Pe* 19 45 14.1410795461 -17 29 27.071420634   10.116 9.302 8.527 7.961 K2III 126 0
33 UCAC2 5726991 Pe* 19 53 49.7800945675 -59 40 00.163969151   13.592 12.620   11.48 KIIvw 41 0
34 BD-18 5550 Pe* 19 58 49.7370363913 -18 12 11.142309703 10.18 10.03 9.35 9.04 8.74 CEMP-no 160 0
35 BPS CS 22873-0166 Pe* 20 19 22.0361305437 -61 30 15.121053020   12.818 11.802 11.52 10.57 KIIvw 44 0
36 BPS CS 22885-0096 Pe* 20 20 51.1729562140 -39 53 30.235406812   14.02 13.33     CEMP-no 81 0
37 BPS CS 22897-0008 Pe* 21 03 11.8563237064 -65 05 08.852932036   14.02 13.33     CEMP-no 61 0
38 BPS CS 29506-0007 Pe* 21 20 28.6541606696 -20 46 22.955747614     14.18     ~ 28 0
39 BPS CS 29506-0090 Pe* 21 30 28.8706794433 -22 10 41.578963371     14.33     ~ 25 0
40 BPS CS 29495-0041 Pe* 21 36 33.2901533828 -28 18 48.439267198 14.111 14.15 13.34   12.222 ~ 30 0
41 HE 2141-3741 Pe* 21 44 51.1647173336 -37 27 55.017357431   14.10 13.47     CEMP-no 50 0
42 BPS CS 22948-0093 Pe* 21 50 31.5179802313 -41 07 49.353957554   15.54 15.18     ~ 32 0
43 BPS CS 22956-0050 Pe* 21 58 05.8339798575 -65 13 27.160917994   14.95 14.25 13.745 13.211 CEMP-no 34 0
44 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
45 BPS CS 22965-0054 Pe* 22 06 30.2933577439 -02 32 34.433172529   15.69 15.07 14.732 14.072 CEMP-no 32 0
46 BPS CS 22892-0052 Pe* 22 17 01.6558480594 -16 39 27.051900047   14.03 13.20 13.06 12.19 KIIvw 400 0
47 BPS CS 29516-0041 Pe* 22 21 48.8261125099 +02 28 44.864481048 13.291 13.4 12.74 12.325 12.013 ~ 34 0
48 BPS CS 29516-0024 Pe* 22 26 15.3575399312 +02 51 46.325239449   14.43 13.57 13.011 12.416 ~ 31 0
49 BPS CS 29491-0053 Pe* 22 36 56.2964405478 -28 31 06.577841168   13.76 12.92 12.380 11.812 ~ 30 0
50 BPS CS 22888-0031 Pe* 23 11 32.4788632961 -35 26 42.874207261   15.31 14.90     CEMP-no 31 0
51 HE 2323-0256 Pe* 23 26 29.8073543039 -02 39 58.037206596   15.12 14.36   13.358 CEMP-no 166 0
52 BPS CS 22966-0011 Pe* 23 35 07.0484328903 -30 22 54.279012782 14.694 14.97 14.55     ~ 24 0
53 HE 2334-0604 Pe* 23 37 28.6873335486 -05 47 56.594686365   14.03 13.28 12.768 12.249 KIIvw 66 0
54 BPS CS 22966-0057 Pe* 23 48 57.7535714010 -29 39 22.828517864 14.759   14.32   13.512 ~ 31 0
55 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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2019.09.19-23:47:51

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