J/ApJ/798/110 Equivalent widths of LAMOST metal-poor stars (Li+, 2015)
Spectroscopic analysis of metal-poor stars from LAMOST: early results.
Li H.-N., Zhao G., Christlieb N., Wang L., Wang W., Zhang Y., Hou Y.,
Yuan H.
<Astrophys. J., 798, 110 (2015)>
=2015ApJ...798..110L 2015ApJ...798..110L
ADC_Keywords: Abundances ; Equivalent widths ; Radial velocities ;
Stars, metal-deficient
Keywords: Galaxy: halo; stars: abundances; stars: Population II
Abstract:
We report on early results from a pilot program searching for
metal-poor stars with LAMOST and follow-up high-resolution observation
acquired with the MIKE spectrograph attached to the Magellan II
telescope. We performed detailed abundance analysis for eight objects
with iron abundances [Fe/H]←2.0, including five extremely metal-poor
(EMP; [Fe/H]←3.0) stars with two having [Fe/H]←3.5. Among these
objects, three are newly discovered EMP stars, one of which is
confirmed for the first time with high-resolution spectral
observations. Three program stars are regarded as carbon-enhanced
metal-poor (CEMP) stars, including two stars with no enhancement in
their neutron-capture elements, which thus possibly belong to the
class of CEMP-no stars; one of these objects also exhibits significant
enhancement in nitrogen, and is thus a potential carbon and
nitrogen-enhanced metal-poor star. The [X/Fe] ratios of the sample
stars generally agree with those reported in the literature for other
metal-poor stars in the same [Fe/H] range. We also compared the
abundance patterns of individual program stars with the average
abundance pattern of metal-poor stars and find only one chemically
peculiar object with abundances of at least two elements (other than C
and N) showing deviations larger than 0.5 dex. The distribution of
[Sr/Ba] versus [Ba/H] agrees that an additional nucleosynthesis
mechanism is needed aside from a single r-process. Two program stars
with extremely low abundances of Sr and Ba support the prospect that
both main and weak r-processes may have operated during the early
phase of Galactic chemical evolution. The distribution of [C/N] shows
that there are two groups of carbon-normal giants with different
degrees of mixing. However, it is difficult to explain the observed
behavior of the [C/N] of the nitrogen-enhanced unevolved stars based
on current data.
Description:
For eight of the candidates selected in the Large Sky Area
Multi-Object fiber Spectroscopic Telescope (LAMOST) DR1 (Luo et al.
2015arXiv150501570L 2015arXiv150501570L) high-resolution spectra were acquired during two
runs in 2013 August and 2013 December with the Magellan Inamori
Kyocera Echelle spectrograph (MIKE) at the Magellan-Clay Telescope at
Las Campanas Observatory (R∼35000 in the blue spectral range
(3300-4900Å) and R∼28000 in the red spectral range
(4900-9400Å)).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 72 8 Log of the Magellan/MIKE observations
table2.dat 198 416 Equivalent width measurements and line-by-line
abundances
table3.dat 51 8 Adopted stellar parameters of the program stars
table4.dat 179 24 Mean abundances for the studied stars
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See also:
J/A+A/570/A107 : WDMS from LAMOST DR1 (Ren+, 2014)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/762/27 : Most metal-poor stars. III. [Fe/H]≤-3.0 stars (Yong+, 2013)
J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)
J/ApJ/762/25 : The most metal-poor stars in HES and SDSS. I. (Norris+, 2013)
J/ApJ/742/54 : CASH project II. 14 extremely metal-poor stars (Hollek+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/ApJ/724/341 : Nucleosynthesis of massive metal-free stars (Heger+, 2010)
J/A+A/501/519 : Extremely metal-poor star abundances (Bonifacio+, 2009)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/A+A/484/721 : HES survey. IV. Candidate metal-poor stars (Christlieb+, 2008)
J/ApJ/658/1203 : Nitrogen-enhanced metal-poor stars (Johnson+, 2007)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
J/ApJ/652/1585 : Bright metal-poor stars from HES survey (Frebel+, 2006)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)
J/AJ/117/981 : Estimation of stellar metal abundance. II. (Beers+, 1999)
J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- --- [LAMOST]
8- 17 A10 --- ID Identifier (JHHMM+DDMM;
in Simbad)
19- 20 I2 h RAh Hour of right ascension (J2000)
22- 23 I2 min RAm Minute of right ascension (J2000)
25- 29 F5.2 s RAs Second of right ascension (J2000)
31 A1 --- DE- Sign of declination (J2000)
32- 33 I2 deg DEd Degree of declination (J2000)
35- 36 I2 arcmin DEm Arcminute of declination (J2000)
38- 41 F4.1 arcsec DEs Arcsecond of declination (J2000)
43- 47 F5.2 mag rmag [10.8/15] r-band magnitude
49- 56 A8 "YYYY/MMM" Date Magellan/MIKE observation date
58- 61 I4 s Exp [360/2700] Exposure time
63- 65 I3 --- S/N [43/106] Signal to noise ratio at
λ∼4500Å (pixel-1)
67- 72 F6.1 km/s RV [-325/122] Radial velocity
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Ion identifier
7- 13 F7.2 0.1nm lambda [3566.3/7699] Wavelength in Angstroms
15- 19 F5.2 eV ExPot [0/4.5] Excitation potential χ
22- 27 F6.3 [-] log(gf) [-5/0.7]? Log of oscillator strength
29- 33 F5.1 10-13m EW1 ? Equivalenth width in J0006+1057 (mÅ)
34 A1 --- f_EW1 [s] s=synthetic-derived abundance in EW1
36- 40 F5.2 [-] logAb1 [-3/5.1]? Log(ε(X)) in J0006+1057
42- 46 F5.2 [-] dev1 ? Deviation of J0006+1057 abundance (1)
48- 52 F5.1 10-13m EW2 ? Equivalenth width in J0102+0428 (mÅ)
53 A1 --- f_EW2 [s] s=synthetic-derived abundance in EW2
55- 59 F5.2 [-] logAb2 [-2.2/5.4]? Log(ε(X)) in J0102+0428
61- 65 F5.2 [-] dev2 ? Deviation of J0102+0428 abundance (1)
67- 71 F5.1 10-13m EW3 ? Equivalenth width in J0126+0135 (mÅ)
72 A1 --- f_EW3 [s] s=synthetic-derived abundance in EW3
74- 78 F5.2 [-] logAb3 [-2.7/4.6]? Log(ε(X)) in J0126+0135
80- 84 F5.2 [-] dev3 ? Deviation of J0126+0135 abundance (1)
86- 90 F5.1 10-13m EW4 ? Equivalenth width in J0257-0022 (mÅ)
91 A1 --- f_EW4 [s] s=synthetic-derived abundance in EW4
93- 97 F5.2 [-] logAb4 [-0.2/6]? Log(ε(X)) in J0257-0022
99-103 F5.2 [-] dev4 ? Deviation of J0257-0022 abundance (1)
105-109 F5.1 10-13m EW5 ? Equivalenth width in J0326+0202 (mÅ)
110 A1 --- f_EW5 [s] s=synthetic-derived abundance in EW5
112-116 F5.2 [-] logAb5 [-2.6/5.3]? Log(ε(X)) in J0326+0202
118-122 F5.2 [-] dev5 ? Deviation of J0326+0202 abundance (1)
124-128 F5.1 10-13m EW6 ? Equivalenth width in J0343-0227 (mÅ)
129 A1 --- f_EW6 [s] s=synthetic-derived abundance in EW6
131-135 F5.2 [-] logAb6 [-2.1/5.6]? Log(ε(X)) in J0343-0227
137-141 F5.2 [-] dev6 ? Deviation of J0343-0227 abundance (1)
143-147 F5.1 10-13m EW7 ? Equivalenth width in J1626+1721 (mÅ)
148 A1 --- f_EW7 [s] s=synthetic-derived abundance in EW7
150-154 F5.2 [-] logAb7 [-0.9/5.1]? Log(ε(X)) in J1626+1721
156-160 F5.2 [-] dev7 ? Deviation of J1626+1721 abundance (1)
162-166 F5.1 10-13m EW8 ? Equivalenth width in J1709+1616 (mÅ)
167 A1 --- f_EW8 [s] s=synthetic-derived abundance in EW8
169-173 F5.2 [-] logAb8 [-1.6/4.3]? Log(ε(X)) in J1709+1616
175-179 F5.2 [-] dev8 ? Deviation of J1709+1616 abundance (1)
181-185 F5.1 10-13m EW9 ? Equivalenth width in J2113-0212 (mÅ) (2)
186 A1 --- f_EW9 [s] s=synthetic-derived abundance in EW9
188-192 F5.2 [-] logAb9 [-0.4/5.7]? Log(ε(X)) in J2113-0212 (2)
194-198 F5.2 [-] dev9 ? Deviation of J2113-0212 abundance (1)
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Note (1): difference between the abundance derived from each individual
atomic line and the average abundance of corresponding species
(Haining Li, private communication)
Note (2): this star (J211308.3-021224) is a RR Lyr, and was removed from
the final sample.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- --- [LAMOST]
8- 17 A10 --- ID Identifier (JHHMM+DDMM;
in Simbad)
19- 22 I4 K Teff1 [4330/6330] MIKE effective temperature
24- 26 F3.1 [cm/s2] logg1 [0.1/4.2] MIKE surface gravity
28- 32 F5.2 [Sun] [Fe/H]1 [-3.8/-2.2] MIKE metallicity
34- 36 F3.1 km/s Vt [1.5/2.8] MIKE microturbulent velocity
38- 41 I4 K Teff2 [4795/6260] LAMOST effective temperature
43- 45 F3.1 [cm/s2] logg2 [1.2/3.6] LAMOST surface gravity
47- 51 F5.2 [Sun] [Fe/H]2 [-3.4/-2.5] LAMOST metallicity
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Ion or molecule designation
7- 11 F5.2 [-] logAb0 Abundance in the Sun logε(X)☉
13- 17 F5.2 [-] logAb1 ?=- Log(ε(X)) in J0006+1057
19- 23 F5.2 [Sun] [X/Fe]1 ?=- Abundance relative to Fe
25- 28 F4.2 [Sun] e_[X/Fe]1 ?=- Mean error on [X/Fe]
30- 32 I3 --- N1 ?=- Number of lines used to derive [X/Fe]1
34- 38 F5.2 [-] logAb2 ?=- Log(ε(X)) in J0102+0428
40- 44 F5.2 [Sun] [X/Fe]2 ?=- Abundance relative to Fe
46- 49 F4.2 [Sun] e_[X/Fe]2 ?=- Mean error on [X/Fe]
51- 53 I3 --- N2 ?=- Number of lines used to derive [X/Fe]2
55- 59 F5.2 [-] logAb3 ?=- Log(ε(X)) in J0126+0135
61- 65 F5.2 [Sun] [X/Fe]3 ?=- Abundance relative to Fe
67- 70 F4.2 [Sun] e_[X/Fe]3 ?=- Mean error on [X/Fe]
72- 74 I3 --- N3 ?=- Number of lines used to derive [X/Fe]3
76- 80 F5.2 [-] logAb4 ?=- Log(ε(X)) in J0257-0022
82- 86 F5.2 [Sun] [X/Fe]4 ?=- Abundance relative to Fe
88- 91 F4.2 [Sun] e_[X/Fe]4 ?=- Mean error on [X/Fe]
93- 95 I3 --- N4 ?=- Number of lines used to derive [X/Fe]4
97-101 F5.2 [-] logAb5 ?=- Log(ε(X)) in J0326+0202
103-107 F5.2 [Sun] [X/Fe]5 ?=- Abundance relative to Fe
109-112 F4.2 [Sun] e_[X/Fe]5 ?=- Mean error on [X/Fe]
114-116 I3 --- N5 ?=- Number of lines used to derive [X/Fe]5
118-122 F5.2 [-] logAb6 ?=- Log(ε(X)) in J0343-0227
124-128 F5.2 [Sun] [X/Fe]6 ?=- Abundance relative to Fe
130-133 F4.2 [Sun] e_[X/Fe]6 ?=- Mean error on [X/Fe]
135-137 I3 --- N6 ?=- Number of lines used to derive [X/Fe]6
139-143 F5.2 [-] logAb7 ?=- Log(ε(X)) in J1626+1721
145-149 F5.2 [Sun] [X/Fe]7 ?=- Abundance relative to Fe
151-154 F4.2 [Sun] e_[X/Fe]7 ?=- Mean error on [X/Fe]
156-158 I3 --- N7 ?=- Number of lines used to derive [X/Fe]7
160-164 F5.2 [-] logAb8 ?=- Log(ε(X)) in J1709+1616
166-170 F5.2 [Sun] [X/Fe]8 ?=- Abundance relative to Fe
172-175 F4.2 [Sun] e_[X/Fe]8 ?=- Mean error on [X/Fe]
177-179 I3 --- N8 ?=- Number of lines used to derive [X/Fe]8
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 18-May-2015