2010A&A...522A..26S


Query : 2010A&A...522A..26S

2010A&A...522A..26S - Astronomy and Astrophysics, volume 522, A26-26 (2010/11-1)

The metal-poor end of the Spite plateau. I. Stellar parameters, metallicities, and lithium abundances.

SBORDONE L., BONIFACIO P., CAFFAU E., LUDWIG H.-G., BEHARA N.T., GONZALEZ HERNANDEZ J.I., STEFFEN M., CAYREL R., FREYTAG B., VAN'T VEER C., MOLARO P., PLEZ B., SIVARANI T., SPITE M., SPITE F., BEERS T.C., CHRISTLIEB N., FRANCOIS P. and HILL V.

Abstract (from CDS):

The primordial nature of the Spite plateau is at odds with the WMAP satellite measurements, implying a primordial Li production at least three times higher than observed. It has also been suggested that A(Li) might exhibit a positive correlation with metallicity below [Fe/H]~-2.5. Previous samples studied comprised few stars below [Fe/H]=-3. We present VLT-UVES Li abundances of 28 halo dwarf stars between [Fe/H]=-2.5 and -3.5, ten of which have [Fe/H]←3. We determined stellar parameters and abundances using four different Teff scales. The direct infrared flux method was applied to infrared photometry. Hα wings were fitted with two synthetic grids computed by means of 1D LTE atmosphere models, assuming two different self-broadening theories. A grid of Hα profiles was finally computed by means of 3D hydrodynamical atmosphere models. The LiI doublet at 670.8nm has been used to measure A(Li) by means of 3D hydrodynamical NLTE spectral syntheses. An analytical fit of A(Li)_3D, NLTE_ as a function of equivalent width, Teff , logg, and [Fe/H] has been derived and is made available. We confirm previous claims that A(Li) does not exhibit a plateau below [Fe/H]=-3. We detect a strong positive correlation with [Fe/H] that is insensitive to the choice of Teff estimator. From a linear fit, we infer a steep slope of about 0.30dex in A(Li) per dex in [Fe/H], which has a significance of 2-3σ. The slopes derived using the four Teff estimators are consistent to within 1σ. A significant slope is also detected in the A(Li)-Teff plane, driven mainly by the coolest stars in the sample (Teff <6250), which appear to be Li-poor. However, when we remove these stars the slope detected in the A(Li)-[Fe/H] plane is not altered significantly. When the full sample is considered, the scatter in A(Li) increases by a factor of 2 towards lower metallicities, while the plateau appears very thin above [Fe/H]=-2.8. At this metallicity, the plateau lies at <A(Li)3D,NLTE≥2.199±0.086. The meltdown of the Spite plateau below [Fe/H]~-3 is established, but its cause is unclear. If the primordial A(Li) were that derived from standard BBN, it appears difficult to envision a single depletion phenomenon producing a thin, metallicity independent plateau above [Fe/H]=-2.8, and a highly scattered, metallicity dependent distribution below. That no star below [Fe/H]=-3 lies above the plateau suggests that they formed at plateau level and experienced subsequent depletion.

Abstract Copyright:

Journal keyword(s): nuclear reactions, nucleosynthesis, abundances - Galaxy: halo - Galaxy: abundances - cosmology: observations - stars: Population II

VizieR on-line data: <Available at CDS (J/A+A/522/A26): table2.dat table3.dat table4.dat>

Simbad objects: 36

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Number of rows : 36
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 SB 44 SB* 00 07 37.5160975025 -35 31 17.710203728   13.23 12.76 12.76   sdF 78 0
2 BPS BS 17570-0063 Pe* 00 20 36.1934507252 +23 47 37.625665043   14.84 14.51     ~ 24 0
3 BPS CS 29527-0015 Pe* 00 29 10.6813715074 -19 10 07.306464364   14.61 14.24     CEMP-no 53 0
4 HE 0027-3613 Pe* 00 30 15.9613306172 -35 56 51.230873749     14.74     ~ 28 0
5 BPS CS 22882-0027 PM* 00 38 09.7945750360 -31 47 58.313113890   15.53 15.11     ~ 5 0
6 GD 657 PM* 00 51 26.1729018743 -38 12 17.886998870   13.62 13.20     ~ 6 0
7 GD 678 PM* 01 06 40.6174528703 -24 58 41.890459578   14.38 14.01 13.668 13.375 CEMP-no 18 0
8 BPS CS 29518-0020 * 01 12 13.2161077183 -31 00 05.359705182 14.164 14.41 14.00     ~ 19 0
9 BPS CS 29518-0043 * 01 18 38.3021781706 -30 41 02.851142792 14.730 14.94 14.57     ~ 24 0
10 BPS CS 22953-0037 Pe* 01 25 06.6511385034 -59 16 00.741420364   14.01 13.64   13.13 CEMP-no 40 0
11 HE 0148-2611 Pe* 01 50 59.6230164864 -25 57 03.083300304 14.574 14.824 14.45     ~ 12 0
12 HE 0233-0343 Pe* 02 36 29.7931232841 -03 30 06.028585140   15.867 15.430 15.171 14.818 CEMP-no 29 0
13 BPS CS 31061-0032 Pe* 02 38 43.3010009273 +03 19 02.564348687   14.30 13.90 13.581 13.290 ~ 26 0
14 BPS CS 22177-0009 Pe* 04 07 40.6490023717 -25 02 43.969982222   14.67 14.27     ~ 31 0
15 HE 0926-0508 Pe* 09 28 55.3516802855 -05 21 40.489677426 12.410 12.34 12.194 11.895 11.617 ~ 15 0
16 HE 0945-1435 Pe* 09 47 50.6778622747 -14 49 06.861845556   15.73 15.23 15.35   CEMP-mp 9 0
17 HE 1148-0037a HB* 11 50 34.7030608123 -00 53 40.870244331   16.6 16.5     ~ 10 1
18 BPS BS 16076-0006 Pe* 12 48 22.7519780017 +20 56 44.030641966   13.88 13.36 13.115 12.706 ~ 20 0
19 HE 1327-2326 Pe* 13 30 05.9395582011 -23 41 49.699027289 13.761 14.01 13.55 13.50 12.803 CEMP-no 223 0
20 BPS BS 16554-0041 Pe* 14 00 54.4741225648 +22 46 42.087338110 14.317 14.548 14.230     ~ 22 0
21 HE 1413-1954 Pe* 14 16 04.7121122481 -20 08 54.090322054     15.235   14.593 CEMP-no 13 0
22 BPS BS 16968-0061 Pe* 15 01 06.1170779628 +03 42 45.573988083   13.73 13.22 13.39   ~ 30 0
23 UCAC2 31517587 Pe* 15 08 29.6580275604 -00 35 59.273543748   13.37 12.95   12.37 ~ 26 0
24 UCAC3 83-396454 PM* 19 40 52.2304469435 -48 39 23.393899163   14.84 14.46     ~ 4 0
25 BPS CS 22950-0173 PM* 20 35 31.2591932771 -15 53 30.716444601   14.45 14.04     ~ 14 0
26 LP 815-43 PM* 20 38 13.2997980664 -20 26 10.852305467   11.31 10.72     ~ 72 0
27 BPS CS 29506-0007 Pe* 21 20 28.6541606696 -20 46 22.955747614     14.18     ~ 29 0
28 BPS CS 29506-0090 Pe* 21 30 28.8706794433 -22 10 41.578963371     14.33     ~ 27 0
29 BPS CS 22948-0093 Pe* 21 50 31.5179802313 -41 07 49.353957554   15.54 15.18     ~ 34 0
30 BPS CS 22965-0054 Pe* 22 06 30.2933577439 -02 32 34.433172529   15.69 15.07 14.732 14.072 CEMP-no 34 0
31 UCAC2 33855992 * 22 25 40.4739849982 +05 37 37.445579574   15.57 15.02     ~ 5 0
32 UCAC2 20056019 * 22 28 49.8435566734 -28 57 01.570961184   13.86 13.48   12.83 ~ 13 0
33 UCAC2 16733845 * 22 47 23.3108210278 -35 32 39.582815684   14.79 14.43     ~ 4 0
34 BPS CS 22888-0031 Pe* 23 11 32.4788632960 -35 26 42.874207261   15.31 14.90     CEMP-no 33 0
35 BPS CS 22966-0011 Pe* 23 35 07.0484328903 -30 22 54.279012782 14.694 14.97 14.55     ~ 26 0
36 SB 966 Pe* 23 53 40.2977653893 -26 58 43.988331934   13.50 13.050     sdF/G? 35 0

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2021.10.27-22:18:39

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