2016A&A...593A..28F

Query : 2016A&A...593A..28F

2016A&A...593A..28F - Astronomy and Astrophysics, volume 593A28-28 (2016/9-1)

Deep SDSS optical spectroscopy of distant halo stars. III. Chemical analysis of extremely metal-poor stars.

FERNANDEZ-ALVAR E., ALLENDE PRIETO C., BEERS T.C., LEE Y.S., MASSERON T. and SCHNEIDER D.P.

Abstract (from CDS):

Aims. We present the results of an analysis of 107 extremely metal-poor (EMP) stars with metallicities lower than [Fe/H]=-3.0, identified in medium-resolution spectra in the Sloan Digital Sky Survey (SDSS). Our analysis provides estimates of the stellar effective temperatures and surface gravities, as well as iron, calcium, and magnesium abundances.
Methods. We followed the same method as in previous papers of this series. The method is based on comparisons of the observed spectra with synthetic spectra. The abundances of Fe, Ca, and Mg were determined by fitting spectral regions that are dominated by lines of each element. In addition, we present a technique to determine upper limits for elements whose features are not detected in a given spectrum. We also analyzed our sample with the SEGUE stellar parameter pipeline to obtain additional determinations of the atmospheric parameters and iron and alpha-element abundances, which we thend compare with ours. In addition, we used these parameters to infer [C/Fe] ratios.
Results. Ca is typically the only element in these spectra with a moderate to low signal-to-noise ratio and medium resolution in this metallicity regime with lines that are sufficiently strong to reliably measure its abundance. Fe and Mg exhibit weaker features that in most cases only provide upper limits. We measured [Ca/Fe] and [Mg/Fe] for EMP stars in the SDSS spectra and conclude that most of the stars exhibit the typical enhancement level for α-elements, ~+0.4, although some stars for which only [Fe/H] upper limits could be estimated indicate higher [α/Fe] ratios. We also find that 26% of the stars in our sample can be classified as carbon-enhanced metal-poor (CEMP) stars and that the frequency of CEMP stars also increases with decreasing metallicity, as has been reported for previous samples. We identify a rare, bright (g=11.90) EMP star, SDSS J134144.61+474128.6, with [Fe/H]=-3.27, [C/Fe]=+0.95, and elevated magnesium ([Mg/Fe]=+0.62), an abundance pattern typical of CEMP-no stars.

Abstract Copyright: © ESO 2016

Journal keyword(s): stars: abundances - stars: Population III - methods: data analysis - catalogs - Galaxy: halo - stars: carbon

VizieR on-line data: <Available at CDS (J/A+A/593/A28): table4-6.dat>

Simbad objects: 108

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Number of rows : 108
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 SDSS J003529.36-111405.2 Pe* 00 35 29.3586615984 -11 14 05.263352304           F5 4 0
2 SDSS J003910.76+082821.8 Pe* 00 39 10.7642330664 +08 28 21.839916360           ~ 1 0
3 SDSS J004705.28+233956.0 Pe* 00 47 05.2662656136 +23 39 56.051316396           F3/F5V 1 0
4 SDSS J005420.85-003905.4 Pe* 00 54 20.8592944392 -00 39 05.381743320           F5 2 0
5 SDSS J011323.60+002631.6 Pe* 01 13 23.6021020440 +00 26 31.597662732           F5 5 0
6 SDSS J013257.20+252558.5 Pe* 01 32 57.1994739624 +25 25 58.535602032           F0V 3 0
7 SDSS J013643.25+010525.4 Pe* 01 36 43.2535693416 +01 05 25.556126712           F0V 2 0
8 SDSS J014036.21+234458.1 Pe* 01 40 36.2207485632 +23 44 58.206182748   15.6       CEMP-no 40 0
9 SDSS J014451.69+333127.7 Pe* 01 44 51.6959198064 +33 31 28.263882684           F2III 3 0
10 SDSS J021958.24-084955.8 Pe* 02 19 58.2485399976 -08 49 55.810988256           A0 4 0
11 SDSS J022534.63+233504.5 Pe* 02 25 34.6309000320 +23 35 04.574956200           A0 1 0
12 SDSS J022654.58-083951.6 Pe* 02 26 54.5744743392 -08 39 51.666276420           F5 1 0
13 SDSS J023248.01+003735.3 Pe* 02 32 48.0132004272 +00 37 35.433906996           F2V 3 0
14 SDSS J023944.44+284349.7 Pe* 02 39 44.4506827464 +28 43 49.745019468           F2 1 0
15 SDSS J024458.86+011823.9 Pe* 02 44 58.8548531424 +01 18 23.995245528           F2III 2 0
16 [LCB92] 0257+0055 Pe* 02 59 38.0501216208 +01 07 35.666169564   18.44 18.03     F5 5 0
17 [CR2000b] 18062 Pe* 02 59 56.4233033256 +00 57 13.484505204   16.98 16.34   15.05 F9 13 0
18 SDSS J031119.96+060850.8 Pe* 03 11 19.9431175560 +06 08 51.021216060           F5 1 0
19 SDSS J031259.10-061957.1 Pe* 03 12 59.1060430992 -06 19 57.113395788           F5 3 0
20 SDSS J031357.33+050741.2 Pe* 03 13 57.3334631520 +05 07 41.315623644           F5 1 0
21 SDSS J031745.82+002304.2 Pe* 03 17 45.8273235048 +00 23 04.178253480           A0 9 0
22 SDSS J033146.90+182530.7 Pe* 03 31 46.9027460208 +18 25 30.725654628           F2 2 0
23 SDSS J035622.42+114705.4 Pe* 03 56 22.4193981432 +11 47 05.580484656           F5 2 0
24 SDSS J045637.24-044123.0 Pe* 04 56 37.2395545056 -04 41 22.963194204           F5 2 0
25 SDSS J051803.47+180544.0 Pe* 05 18 03.4631907048 +18 05 44.150616024           A0p 2 0
26 SDSS J063055.58+255243.7 Pe* 06 30 55.5706644768 +25 52 43.780895400           B9 7 0
27 SDSS J074449.38+471237.3 Pe* 07 44 49.3840491696 +47 12 37.541264328           F8III 3 0
28 SDSS J080057.48+070550.5 Pe* 08 00 57.4874424408 +07 05 50.570342016           F2 4 0
29 SDSS J080428.21+515303.1 Pe* 08 04 28.2124979952 +51 53 03.063950340           A0 7 0
30 SDSS J082452.06+645145.6 Pe* 08 24 52.0439832120 +64 51 45.715809636           A0 1 0
31 SDSS J082511.45+163459.9 Pe* 08 25 11.4567356976 +16 35 00.012656940           F5 6 0
32 SDSS J083235.90+134538.3 Pe* 08 32 35.9040434232 +13 45 38.341561536           F5 3 0
33 SDSS J084214.91+195254.9 Pe* 08 42 14.9164174560 +19 52 55.094955888           ~ 2 0
34 SDSS J085656.23+034410.3 Pe* 08 56 56.2322580216 +03 44 10.349834208           F5 2 0
35 SDSS J085804.66+034515.7 Pe* 08 58 04.6610825016 +03 45 15.739287768           F5 3 0
36 SDSS J085934.48+040232.4 Pe* 08 59 34.4763748056 +04 02 32.384881392           F5 5 0
37 UCAC4 750-045098 Pe* 09 13 08.4238881888 +59 57 02.545178868   16.62 15.93 15.89   F3IV 4 0
38 SDSS J091844.56+431219.3 Pe* 09 18 44.5692358632 +43 12 19.411685064           F5 1 0
39 2MASS J09214741+2619366 Pe* 09 21 47.3412754955 +26 19 36.606298051           F2III 3 0
40 SDSS J092540.08+094104.3 Pe* 09 25 40.0780682400 +09 41 04.378526376           F5 1 0
41 SDSS J092931.26+592711.7 Pe* 09 29 31.2654471432 +59 27 11.740826124           F3/F5V 2 0
42 SDSS J093231.65+085037.1 Pe* 09 32 31.6528711632 +08 50 37.134201876           F5 1 0
43 SDSS J093339.24+310245.4 Pe* 09 33 39.2492778168 +31 02 45.416743224           F5 2 0
44 SDSS J100401.24+420150.4 Pe* 10 04 01.2517484568 +42 01 50.485765548           G0III 2 0
45 SDSS J100537.71+022734.1 Pe* 10 05 37.7143809600 +02 27 34.207203240           F5 1 0
46 SDSS J101600.42+172901.1 Pe* 10 16 00.4297208736 +17 29 01.424880528           F5 2 0
47 SDSS J102328.72+352919.0 Pe* 10 23 28.7228593536 +35 29 19.117904244           A0 1 0
48 SDSS J102628.72+435742.0 Pe* 10 26 28.7369187576 +43 57 42.041128500           F0V 4 0
49 SDSS J104617.20+172712.3 RG* 10 46 17.2095172368 +17 27 12.290510520           KIII 3 0
50 SDSS J104631.66+283819.7 Pe* 10 46 31.6696595976 +28 38 19.777141680           F5 1 0
51 SDSS J104702.87+214308.4 Pe* 10 47 02.8794884328 +21 43 08.442985368           F5 2 0
52 SDSS J110445.18+670752.0 Pe* 11 04 45.1872665592 +67 07 52.041265320           F5 2 0
53 SDSS J110827.88+613419.0 Pe* 11 08 27.8796079128 +61 34 19.169256288           A0 2 0
54 SDSS J111104.14+413942.6 Pe* 11 11 04.1462164944 +41 39 42.733256292           F5 2 0
55 SDSS J112805.85+204651.2 Pe* 11 28 05.8567097664 +20 46 51.235030560           ~ 2 0
56 SDSS J112827.62-002232.1 RG* 11 28 27.6245424480 -00 22 32.223697356           KIII 3 0
57 SDSS J115019.10+135535.4 RG* 11 50 19.1032511064 +13 55 35.477128992           KIII 4 0
58 SDSS J115221.93+385608.9 Pe* 11 52 21.9368084376 +38 56 09.000034764           F5 2 0
59 SDSS J115525.43+474420.1 Pe* 11 55 25.4418910272 +47 44 20.154828948           F5 1 0
60 SDSS J115906.18+542512.6 Pe* 11 59 06.1746294024 +54 25 12.641580660           A0 7 0
61 SDSS J120441.38+120111.5 Pe* 12 04 41.3884587048 +12 01 11.514049212           A0 17 0
62 SDSS J120858.66+302312.9 Pe* 12 08 58.6562479104 +30 23 13.081804620           F5 1 0
63 SDSS J121042.14+402645.2 Pe* 12 10 42.1530190992 +40 26 45.231816660           F5 1 0
64 SDSS J123404.57+134411.4 Pe* 12 34 04.5775389960 +13 44 11.402652012           A0 3 0
65 SDSS J125050.82+102520.2 Pe* 12 50 50.8286174592 +10 25 20.240640948           F5 3 0
66 SDSS J125330.45+191331.1 Pe* 12 53 30.4509023568 +19 13 31.182883680           F5 1 0
67 2MASS J13061549+3905355 Pe* 13 06 15.4909891992 +39 05 35.447607420           F5 3 0
68 ZTF J132146.90+322733.2 EB* 13 21 46.899 +32 27 33.27           F5 3 0
69 HE 1320+0139 Pe* 13 22 50.6004129672 +01 23 42.949936212   16.72 16.08 15.40   F5 12 0
70 BPS BS 16934-0002 Pe* 13 29 46.5066859200 +16 15 45.145424556   13.733 12.819 12.239 11.670 ~ 17 0
71 LSPM J1341+4741 Pe* 13 41 44.6114760816 +47 41 28.905615168   11.86 11.44     ~ 10 0
72 SDSS J134338.67+484426.6 Pe* 13 43 38.6679996887 +48 44 26.706404692   12.685 12.147 12.114   CEMP 10 0
73 SDSS J134916.87+002622.7 Pe* 13 49 16.8723677016 +00 26 22.789985748           G0III 2 0
74 SDSS J135331.01-032930.2 Pe* 13 53 31.0183504440 -03 29 30.125467248           O9IV 4 0
75 SDSS J141249.08+013206.7 Pe* 14 12 49.0795398960 +01 32 06.680523624           A0III 4 0
76 PB 3654 Pe* 14 29 28.2978460896 +29 55 42.709989648   17       F5 4 0
77 SDSS J143914.32+212259.4 Pe* 14 39 14.3232092256 +21 22 59.393327988           F5 2 0
78 SDSS J144442.54+214647.0 Pe* 14 44 42.5380927296 +21 46 47.051717016           F5 1 0
79 SDSS J144726.06+224552.7 Pe* 14 47 26.0846911152 +22 45 52.620949260           F5 2 0
80 SDSS J144759.68+001308.3 Pe* 14 47 59.6862267360 +00 13 08.342809176           A0 2 0
81 SDSS J145056.30+234116.4 Pe* 14 50 56.2995375336 +23 41 16.496566800           F5 2 0
82 SDSS J145124.04+093845.2 Pe* 14 51 24.0484168392 +09 38 45.139321644           A0 1 0
83 SDSS J152853.64+065510.2 Pe* 15 28 53.6536759368 +06 55 10.290618192           F5 2 0
84 SDSS J155133.86+260423.0 Pe* 15 51 33.8725088256 +26 04 23.107958940           ~ 2 0
85 SDSS J160142.38+053026.9 Pe* 16 01 42.3870602568 +05 30 26.992995336           F5 2 0
86 SDSS J160431.54+043220.6 Pe* 16 04 31.5475725600 +04 32 20.667005808           F5 2 0
87 SDSS J160926.70+164743.2 Pe* 16 09 26.7094282080 +16 47 43.192581900           F5 2 0
88 SDSS J161313.51+530909.6 Pe* 16 13 13.5241043232 +53 09 09.693368640           CEMP-no 16 0
89 SDSS J165618.30+342523.1 Pe* 16 56 18.3095092680 +34 25 23.051084448           ~ 2 0
90 SDSS J165835.20+272629.5 Pe* 16 58 35.1999885216 +27 26 29.575144140           F5 1 0
91 2MASS J17033961+2836505 Pe* 17 03 39.6056633256 +28 36 50.490780156           F2 12 0
92 SDSS J170555.89+285305.8 Pe* 17 05 55.8935313000 +28 53 05.890577244           F5 2 0
93 SDSS J170743.57+283643.1 Pe* 17 07 43.5761141976 +28 36 43.076611440           F5 4 0
94 SDSS J173302.14+090813.3 Pe* 17 33 02.1475608480 +09 08 13.347812220           F5 1 0
95 SDSS J173532.16+444635.9 Pe* 17 35 32.1641070600 +44 46 35.875194276           F5 7 0
96 SDSS J174235.90+643411.2 Pe* 17 42 35.9128436160 +64 34 11.296900668           G2 1 0
97 SDSS J175028.71+254434.0 Pe* 17 50 28.7214378720 +25 44 34.180303812           F5 1 0
98 SDSS J180516.76+231107.7 Pe* 18 05 16.7676610248 +23 11 07.771456608           F5 1 0
99 SDSS J191104.68+781833.6 Pe* 19 11 04.7131563312 +78 18 33.625515492           F5 2 0
100 SDSS J204524.03+150825.3 Pe* 20 45 24.0355879224 +15 08 25.391104728           F5 2 0
101 SDSS J204735.17+001137.9 Pe* 20 47 35.1759485184 +00 11 37.925326428           A0 1 0
102 SDSS J213242.72+040533.9 Pe* 21 32 42.7219291728 +04 05 33.970393140           O8/O9 1 0
103 SDSS J215731.90+450540.7 Pe* 21 57 31.9168866696 +45 05 40.704309636           F5 1 0
104 SDSS J220646.20-092545.7 Pe* 22 06 46.2048718296 -09 25 45.747895296           F5 12 0
105 SDSS J225629.81+071400.5 Pe* 22 56 29.8152410424 +07 14 00.588383700           F5 2 0
106 SDSS J231319.28+211528.5 Pe* 23 13 19.2863032680 +21 15 28.619665092           sdA: 2 0
107 SDSS J234403.47+151744.6 Pe* 23 44 03.4733408448 +15 17 44.639142000           F5 2 0
108 LP 584-32 Pe* 23 57 18.9066974952 -00 52 47.436045024   16.366 15.636 15.141 14.673 F5 35 0

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