2015A&A...579A..28B


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST15:05:39

2015A&A...579A..28B - Astronomy and Astrophysics, volume 579A, 28-28 (2015/7-1)

TOPoS. II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies.

BONIFACIO P., CAFFAU E., SPITE M., LIMONGI M., CHIEFFI A., KLESSEN R.S., FRANCOIS P., MOLARO P., LUDWIG H.-G., ZAGGIA S., SPITE F., PLEZ B., CAYREL R., CHRISTLIEB N., CLARK P.C., GLOVER S.C.O., HAMMER F., KOCH A., MONACO L., SBORDONE L. and STEFFEN M.

Abstract (from CDS):

In the course of the Turn Off Primordial Stars (TOPoS) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (CEMP) stars. These stars are very common among the stars of extremely low metallicity and provide important clues to the star formation processes. We here present our analysis of six CEMP stars. We want to provide the most complete chemical inventory for these six stars in order to constrain the nucleosynthesis processes responsible for the abundance patterns. We analyse both X-Shooter and UVES spectra acquired at the VLT. We used a traditional abundance analysis based on OSMARCS 1D local thermodynamic equilibrium (LTE) model atmospheres and the turbospectrum line formation code. Calcium and carbon are the only elements that can be measured in all six stars. The range is -5.0≤[Ca/H]< -2.1 and 7.12≤A(C)≤8.65. For star SDSSJ1742+2531 we were able to detect three FeI lines from which we deduced [Fe/H]=-4.80, from four CaII lines we derived [Ca/H]=-4.56, and from synthesis of the G-band we derived A(C)=7.26. For SDSSJ1035+0641 we were not able to detect any iron lines, yet we could place a robust (3σ) upper limit of [Fe/H]< -5.0 and measure the Ca abundance, with [Ca/H]=-5.0, and carbon, A(C)=6.90, suggesting that this star could be even more metal-poor than SDSSJ1742+2531. This makes these two stars the seventh and eighth stars known so far with [Fe/H]< -4.5, usually termed ultra-iron-poor (UIP) stars. No lithium is detected in the spectrum of SDSSJ1742+2531 or SDSSJ1035+0641, which implies a robust upper limit of A(Li)<1.8 for both stars. Our measured carbon abundances confirm the bimodal distribution of carbon in CEMP stars, identifying a high-carbon band and a low-carbon band. We propose an interpretation of this bimodality according to which the stars on the high-carbon band are the result of mass transfer from an AGB companion, while the stars on the low-carbon band are genuine fossil records of a gas

Abstract Copyright:

Journal keyword(s): that has also been enriched by a faint supernova providing carbon cloud, lighter elements. The abundance pattern of the UIP stars shows a large star-to-star scatter in the [X/Ca] ratios for all elements up to aluminium the, this scatter drops for heavier elements and is at most of the order of a factor of two. We propose that this can be explained if these stars are formed from gas that has been chemically enriched by several SNe but, produce the roughly constant [X/Ca] ratios for the heavier elements that, some cases the gas has also been polluted by the ejecta of a faint SN that contributes the lighter elements in variable amounts. The absence of lithium in four of the five known unevolved UIP stars can be explained by a dominant role of fragmentation in the formation of these stars. This would result either in a destruction of lithium in the pre-main-sequence phase, through rotational mixing or to a lack of late accretion from a reservoir of fresh gas. The phenomenon should have varying degrees of efficiency. - stars: Population II - stars: abundances - stars: Population III - Galaxy: abundances - Galaxy: formation - Galaxy: halo

VizieR on-line data: <Available at CDS (J/A+A/579/A28): stars.dat table4.dat>

CDS comments: Fig.6 HE 022-4831 is a misprint for HE 2202-4831 .

Simbad objects: 46

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Number of rows : 46

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 SB 44 SB* 00 07 37.5160975025 -35 31 17.710203728   13.23 12.76 12.76   sdF 75 0
2 HE 0007-1832 Pe* 00 09 52.7814403998 -18 16 12.276852284     15.46     CEMP-no 19 0
3 BPS CS 29527-0015 Pe* 00 29 10.6813715074 -19 10 07.306464364   14.61 14.24     CEMP-no 52 0
4 QSO J0035-0918 QSO 00 35 01.8855808652 -09 18 17.643286882   19.32 19.12     ~ 46 0
5 2MASS J00360218-1043362 Pe* 00 36 02.1763225796 -10 43 36.335842424           CEMP-s 14 0
6 NAME Sculptor Dwarf Galaxy G 01 00 09.4 -33 42 32   9.79 8.6 8.81   ~ 1116 4
7 HE 0107-5240 Pe* 01 09 29.1554552993 -52 24 34.203535506   15.89 15.07 15.10 14.283 CEMP-no 228 0
8 HE 0134-1519 Pe* 01 37 05.3769545718 -15 04 22.792633672   14.937 14.474 14.018 13.683 CEMP-no 14 0
9 BPS CS 22958-0042 Pe* 02 01 07.4296353198 -57 16 58.851945318   14.037 14.52 14.222 13.902 CEMP-no 35 0
10 2MASS J02123845+0137580 Pe* 02 12 38.4777505326 +01 37 58.162393363           CEMP-no 8 0
11 BPS CS 29528-0041 Pe* 02 29 25.2507036195 -18 13 28.042501354 14.83 15.20 14.59 14.67   CEMP-no 25 0
12 2MASS J02362978-0330060 Pe* 02 36 29.7931232841 -03 30 06.028585140   15.867 15.430 15.171 14.818 CEMP-no 28 0
13 NAME Fornax Dwarf Spheroidal G 02 39 59.3 -34 26 57   9.02 7.4     ~ 1473 1
14 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5665 1
15 SMSS J031300.36-670839.3 Pe* 03 13 00.3747490864 -67 08 39.336567558           CEMP-no 84 0
16 G 77-61 Pe* 03 32 38.0871477505 +01 58 00.010460312   15.60 13.90 12.9   dC-J_CH5 124 0
17 HE 0557-4840 Pe* 05 58 39.2661082631 -48 39 56.890701762   16.16 15.45 14.991   CEMP-no 81 0
18 NAME UMa II Galaxy G 08 51 30.0 +63 07 48     13.3     ~ 311 0
19 SDSS J092912.33+023817.0 Pe* 09 29 12.3278971448 +02 38 17.021720615           CEMP-s 9 0
20 NAME Segue 1 G 10 07 03.2 +16 04 25     15.3     ~ 357 1
21 NAME Dwarf Elliptical Galaxy in Sex G 10 13 02.9 -01 36 53   12 10.4     ~ 706 0
22 UCAC3 215-112497 Pe* 10 29 15.1491308300 +17 29 27.926665478         15.98 ~ 91 0
23 SDSS J103556.11+064143.9 Pe* 10 35 56.1164062654 +06 41 44.009615054           CEMP-no 22 0
24 NAME SDSS J1036+1212 Pe* 10 36 49.9302951768 +12 12 19.888898997           CEMP-s 24 0
25 QSO J1134+5742 QSO 11 34 18.9636381629 +57 42 04.725512541   19.62 18.99     ~ 29 0
26 2MASS J11372328+2553543 Pe* 11 37 23.2781180904 +25 53 54.426445070           CEMP-s 3 0
27 G 122-69 PM* 12 03 04.3024960233 +47 19 26.311495351   12.95   12.1   ~ 26 0
28 SDSS J124502.68-073847.1 Pe* 12 45 02.6810071619 -07 38 47.102875949           CEMP-s 10 0
29 LAMOST J131331.18-055212.4 Pe* 13 13 31.1856625664 -05 52 12.533547463   15.055 14.347 13.829   CEMP-no 23 0
30 HE 1327-2326 Pe* 13 30 05.9395582011 -23 41 49.699027289 13.761 14.01 13.55 13.50 12.803 CEMP-no 214 0
31 NAME Bootes II G 13 58 00.0 +12 51 00     15.4     ~ 193 0
32 QSO J1358+6522 QSO 13 58 42.9174456058 +65 22 36.654561109   19.53 19.06     ~ 46 0
33 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 339 0
34 NAME UMi Galaxy G 15 09 11.34 +67 12 51.7   13.60 10.6     ~ 1178 0
35 SDSS J161956.33+170539.9 * 16 19 56.3324517014 +17 05 39.848877795           ~ 5 0
36 NAME Her Dwarf Galaxy G 16 31 02.0 +12 47 30     14.0     ~ 275 1
37 G 139-8 PM* 17 01 43.9815778038 +16 09 03.341478802   11.918 11.470 11.128 10.779 sd:F 44 0
38 NAME Dra dSph G 17 20 14.335 +57 55 16.39   12.40 10.6     ~ 1165 1
39 SDSS J174259.67+253135.8 Pe* 17 42 59.6806116319 +25 31 35.890539509           CEMP-no 19 0
40 NAME SDG G 18 55 03.1 -30 28 42   4.5 3.6     ~ 1737 2
41 HD 340279 PM* 20 24 45.4127587189 +25 03 07.108270663   11.23   10.7   A5 92 0
42 HE 2202-4831 Pe* 22 06 06.00020 -48 16 53.0089   16.3       CEMP-no 12 0
43 HE 2323-0256 Pe* 23 26 29.8073543039 -02 39 58.037206596   15.12 14.36   13.358 CEMP-no 171 0
44 HE 2356-0410 Pe* 23 59 13.1417869434 -03 53 48.220053208   14.39 13.60 13.164 12.713 CEMP-no 81 0
45 NAME Coma Berenices Moving Group MGr ~ ~           ~ 57 0
46 NAME Local Group GrG ~ ~           ~ 6970 0

    Equat.    Gal    SGal    Ecl

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2020.07.04-15:05:39

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