2007A&A...464.1081A


Query : 2007A&A...464.1081A

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 - 2023
#notes
1 BPS BS 17570-0063 Pe* 00 20 36.1923434544 +23 47 37.617775440   14.84 14.51     ~ 24 0
2 BPS CS 29527-0015 Pe* 00 29 10.6814565504 -19 10 07.305102624   14.61 14.24     CEMP-no 55 0
3 HE 0027-3613 Pe* 00 30 15.9610744584 -35 56 51.229784760     14.74     ~ 29 0
4 HD 2796 Pe* 00 31 16.9147531152 -16 47 40.790991624 9.58 9.28 8.50 8.14 8.67 Fw 191 0
5 CD-38 245 Pe* 00 46 36.1954514592 -37 39 33.555030480   12.733 11.929 13.39 10.996 KIIvw 219 0
6 BPS CS 22953-0003 Pe* 01 02 15.8723379360 -61 43 45.836012208   14.43 13.75 13.339 12.886 KIIvw 66 0
7 BPS CS 29518-0020 * 01 12 13.2160928832 -31 00 05.358952296 14.164 14.41 14.00     ~ 19 0
8 BPS CS 29518-0043 * 01 18 38.3021768400 -30 41 02.851310832 14.730 14.94 14.57     ~ 24 0
9 BPS CS 29518-0051 Pe* 01 24 10.0049733024 -28 15 21.115362312 13.567 13.62 13.02 12.594 12.162 ~ 31 0
10 BPS CS 22953-0037 Pe* 01 25 06.6508649808 -59 16 00.742176912   14.01 13.64   13.13 CEMP-no 41 0
11 BPS CS 31082-0001 RG* 01 29 31.1311443552 -16 00 45.495314460 12.527 12.427 11.642 11.189 10.713 CEMP 283 0
12 BPS CS 29528-0041 Pe* 02 29 25.2514644552 -18 13 28.025186448 14.83 15.20 14.59 14.67   CEMP-no 26 0
13 BPS CS 31061-0032 Pe* 02 38 43.3009378608 +03 19 02.563623012   14.30 13.90 13.581 13.290 ~ 26 0
14 HE 0239-1340 Pe* 02 41 42.3721546152 -13 28 10.603797240   14.73 13.97 13.566 13.080 CEMP-no 57 0
15 HE 0305-5442 Pe* 03 06 29.5014981984 -54 30 32.498486568   14.44 13.70 13.212 12.715 KIIvw 74 0
16 2MASS J03142084-1035112 Pe* 03 14 20.8495451808 -10 35 11.277788028   13.54 12.73 12.204 11.693 KIIvw 66 0
17 BPS CS 22177-0009 Pe* 04 07 40.6490981040 -25 02 43.970266068   14.67 14.27     ~ 32 0
18 HE 0409-1212 Pe* 04 12 13.8814287960 -12 05 05.075250072   13.843 12.897   11.764 ~ 65 0
19 BPS CS 22186-0025 Pe* 04 24 32.7982834272 -37 09 02.518136460   14.99 14.24 13.740 13.269 ~ 35 0
20 Wolf 1492 Pe* 13 40 02.4921849768 -00 02 18.750053436 11.601 11.832 11.451 11.184 10.892 sdF0: 277 0
21 BPS BS 16467-0062 Pe* 13 42 00.6326009568 +17 48 40.826539260   14.69 14.09 13.665 13.216 ~ 47 0
22 BPS BS 16554-0041 Pe* 14 00 54.4740571128 +22 46 42.087313956 14.317 14.548 14.230     ~ 22 0
23 HD 122563 Pe* 14 02 31.8455084952 +09 41 09.944391876 7.47 7.10 6.19 5.37 4.79 G8:III:Fe-5 826 0
24 BPS BS 16477-0003 Pe* 14 32 56.9231765928 +06 46 06.974256288   14.94 14.22 13.727 13.224 ~ 35 0
25 BPS CS 30325-0094 Pe* 14 54 39.2685981792 +04 21 38.099145888   13.02 12.32 11.849 11.376 ~ 45 0
26 BPS BS 16968-0061 Pe* 15 01 06.1171458744 +03 42 45.573411168   13.73 13.22 13.39   ~ 31 0
27 UCAC2 31517587 Pe* 15 08 29.6579865432 -00 35 59.273507796   13.37 12.95   12.37 ~ 26 0
28 BPS CS 22878-0101 Pe* 16 45 31.4513454168 +08 14 45.470265900   14.59 13.79   12.673 KIIvw 58 0
29 BD+17 3248 HB* 17 28 14.4690179544 +17 30 35.847574776   10.02 9.34     KIIvw 217 0
30 BPS CS 22891-0209 Pe* 19 42 02.1802427088 -61 03 44.534898612   13.03 12.18     KIIvw 56 0
31 UCAC2 7177623 Pe* 19 42 26.8926894816 -56 58 34.059037980   14.27 13.63     ~ 49 0
32 HD 186478 SB* 19 45 14.1409752672 -17 29 27.071239056   10.116 9.302 8.527 7.961 K2III 148 0
33 UCAC2 5726991 Pe* 19 53 49.7804195664 -59 40 00.163242192   13.592 12.620   11.48 KIIvw 47 0
34 BD-18 5550 Pe* 19 58 49.7371417608 -18 12 11.140126164 10.18 10.03 9.35 9.04 8.74 CEMP-no 172 0
35 BPS CS 22873-0166 Pe* 20 19 22.0362485016 -61 30 15.119987544   12.818 11.802 11.52 10.57 KIIvw 53 0
36 BPS CS 22885-0096 Pe* 20 20 51.1730095656 -39 53 30.234972840   14.02 13.33     CEMP-no 85 0
37 BPS CS 22897-0008 Pe* 21 03 11.8565397504 -65 05 08.852220600   14.02 13.33     CEMP-no 68 0
38 BPS CS 29506-0007 Pe* 21 20 28.6541822328 -20 46 22.955304144     14.18     ~ 31 0
39 BPS CS 29506-0090 Pe* 21 30 28.8706762776 -22 10 41.578379040     14.33     ~ 28 0
40 BPS CS 29495-0041 Pe* 21 36 33.2900452248 -28 18 48.440793960 14.111 14.15 13.34   12.222 ~ 32 0
41 HE 2141-3741 RG* 21 44 51.1647807408 -37 27 55.017356112   14.10 13.47     CEMP-no 54 0
42 BPS CS 22948-0093 Pe* 21 50 31.5180047928 -41 07 49.355148468   15.54 15.18     ~ 36 0
43 BPS CS 22956-0050 Pe* 21 58 05.8340681280 -65 13 27.160682772   14.95 14.25 13.745 13.211 CEMP-no 37 0
44 2MASS J22045836+0401321 Pe* 22 04 58.3605927288 +04 01 32.135832984 14.503 14.25 13.36 12.805 12.259 ~ 32 0
45 BPS CS 22965-0054 Pe* 22 06 30.2933030688 -02 32 34.433318220   15.69 15.07 14.732 14.072 CEMP-no 35 0
46 BPS CS 22892-0052 Pe* 22 17 01.6558764360 -16 39 27.051026544   14.03 13.20 13.06 12.19 KIIvw 438 0
47 BPS CS 29516-0041 Pe* 22 21 48.8262598080 +02 28 44.867730936 13.291 13.4 12.74 12.325 12.013 ~ 38 0
48 BPS CS 29516-0024 Pe* 22 26 15.3575269416 +02 51 46.326341232   14.43 13.57 13.011 12.416 ~ 34 0
49 BPS CS 29491-0053 Pe* 22 36 56.2965716592 -28 31 06.577096368   13.76 12.92 12.380 11.812 ~ 32 0
50 BPS CS 22888-0031 Pe* 23 11 32.4788498208 -35 26 42.872735796   15.31 14.90     CEMP-no 35 0
51 HE 2323-0256 Pe* 23 26 29.8073738880 -02 39 58.036383180   15.12 14.36   13.358 CEMP-no 176 0
52 BPS CS 22966-0011 Pe* 23 35 07.0484945928 -30 22 54.278132700 14.694 14.97 14.55     ~ 27 0
53 HE 2334-0604 RG* 23 37 28.6873103640 -05 47 56.594641632   14.03 13.28 12.768 12.249 KIIvw 69 0
54 BPS CS 22966-0057 Pe* 23 48 57.7540034928 -29 39 22.824085392 14.759   14.32   13.512 ~ 33 0
55 SB 966 Pe* 23 53 40.2978963936 -26 58 43.988391156   13.50 13.050     sdF/G? 36 0

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2023.05.29-00:19:01

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