J/A+A/614/A68 Carbon-enhanced metal-poor stars sample (Caffau+, 2018)
Investigation of a sample of carbon-enhanced metal-poor stars observed
with FORS and GMOS.
Caffau E., Gallagher A.J., Bonifacio P., Spite M., Duffau S.,
Spite F., Monaco L., Sbordone L.
<Astron. Astrophys. 614, A68 (2018)>
=2018A&A...614A..68C 2018A&A...614A..68C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, population II ; Stars, metal-deficient ; Stars, carbon ;
Abundances ; Radial velocities
Keywords: stars: population II - stars: abundances - Galaxy: abundances -
Galaxy: formation - Galaxy: halo
Abstract:
Carbon-enhanced metal-poor (CEMP) stars represent a sizeable fraction
of all known metal-poor stars in the Galaxy. Their formation and
composition remains a significant topic of investigation within the
stellar astrophysics community.
We analysed a sample of low-resolution spectra of 30 dwarf stars,
obtained using the the visual and near UV FOcal Reducer and low
dispersion Spectrograph for the Very Large Telescope (FORS/VLT) of the
European Southern Observatory (ESO) and the Gemini Multi-Object
Spectrographs (GMOS) at the GEMINI telescope, to derive their
metallicity and carbon abundance.
We derived C and Ca from all spectra, and Fe and Ba from the majority
of the stars. Conclusions. We have extended the population statistics
of CEMP stars and have confirmed that in general, stars with a high C
abundance belonging to the high C band show a high Ba-content (CEMP-s
or -r/s), while stars with a normal C-abundance or that are C-rich,
but belong to the low C band, are normal in Ba (CEMP-no).
Description:
We selected a sample of turn-off stars from the Sloan Digital Sky
Survey (SDSS York et al. 2000AJ....120.1579Y 2000AJ....120.1579Y; Yanny et al. 2009, Cat.
J/AJ/137/4377) that were bright enough (g<17) to allow us to secure a
reasonable spectrum quality in a single observing block of 1h.
The FORS spectra have been observed in service mode during the ESO
Programme 099.D-0791, between 01/04/2017 and 16/08/2017.
The GMOS spectra were acquired in service mode on the nights of
21/07/2017 and 25/07/2017.
Table 1 lists the stars we examined here, along with their
coordinates, g-mag, and metallicities derived from Fe abundances
computed using SDSS and FORS/GMOS spectra.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 109 32 Characteristics of the stars analysed in the paper
table2.dat 180 31 Chemical composition of the stars analysed in
the paper
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
J/ApJ/658/367 : Abundances of carbon stars in Galactic halo (Komiya+, 2007)
J/ApJ/658/1203 : Nitrogen-enhanced metal-poor stars (Johnson+, 2007)
J/A+A/509/A93 : Carbon-enhanced metal-poor stars (Masseron+, 2010)
J/A+A/548/A34 : Abundances of Carbon-enhanced metal-poor stars (Allen+, 2012)
J/ApJ/762/27 : Most metal-poor stars. III. 86 [Fe/H]≤-3.0 stars (Yong+ 2013)
J/ApJ/773/33 : Chemical analysis of metal-poor subgiant BD+44 493 (Ito+ 2013)
J/ApJ/788/180 : Very metal-poor stars in the Milky Way's halo (Carollo+, 2014)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/A+A/574/A129 : The First CEMP star in the Sculptor dSph (Skuladottir+, 2015)
J/A+A/581/A22 : 67 CEMP-s stars model analysis (Abate+, 2015)
J/ApJ/814/121 : CASH project. III. The CEMP star HE0414-0343 (Hollek+, 2015)
J/A+A/586/A158 : Binary properties of CH and CEMP stars (Jorissen+, 2016)
J/ApJ/824/L19 : Carbon-enhanced metal-poor star BD+44493 EWs (Roederer+, 2016)
J/ApJ/833/20 : Carbon-enhanced metal-poor (CEMP) star abundances (Yoon+ 2016)
J/A+A/606/A55 : Rotational mixing in CEMP-s stars (Matrozis+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS name of the star (JHHMMSS.ss+DDMMSS.s)
26- 36 F11.7 deg RAdeg Right ascension (J2000)
38- 49 F12.8 deg DEdeg Declination (J2000)
51- 55 F5.2 mag gmag SDSS DR12 g magnitude (1)
57- 71 F15.9 d MJD Modified Julian date
73- 76 I4 km/s RVD ?=- Radial Velocity from SDSS
78 I1 km/s s_RVD ?=- Uncertainty on the Radial Velocity from SDSS
(line-to-line scatter)
80- 83 I4 km/s RVF ?=- Radial Velocity from FORS2 spectra
85- 86 I2 km/s s_RVF ?=- Uncertainty on the Radial Velocity from
FORS2 spectra (line-to-line scatter)
88- 92 F5.2 [-] [M/H]S ?=- Metallicity derived from the SDSS spectra (2)
94- 97 F4.2 [-] s_[M/H]S ?=- Uncertainty on the metallicity derived from
the SDSS spectra (line-to-line scatter)
99-103 F5.2 [-] [Fe/H] ?=- Abundance [Fe/H] derived from the
FORS2 and GMOS spectra (3)
104 A1 --- u_[Fe/H] Uncertainty flag on [Fe/H] (4)
106-109 F4.2 [-] s_[Fe/H] ?=- Uncertainty on the [Fe/H] derived from the
FORS2 and GMOS spectra (line-to-line scatter)
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Note (1): g magnitudes are those used to derive the effective temperatures and
are taken from the SDSS-DR12 (Cat. V/147).
Note (2): [M/H] from SDSS is based on several metallic features
Note (3): [Fe/H] from FORS and GMOS spectra are taken from FeI lines only.
The solar A(Fe)=7.52 adopted is taken from Caffau et al.
(2011, Sol. Phys., 268, 255).
Note (4): for the uncertain cases, the colon in the iron abundance is an
estimate of the uncertainty in the comparison to synthetic spectra.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Star Star name (SDSSJHHMM+DDMM)
15 A1 --- --- [,]
16 I1 --- n_Star [1/2]? Observation number when 2 measurements
19- 22 I4 K Teff effective temperature [K]
26- 29 F4.2 [-] A(Fe) Fe abundance from FeI lines, A(Fe)
32- 35 F4.2 [-] e_A(Fe) Uncertainty on Fe abundance from FeI lines
36 A1 --- ueA(Fe) Uncertainty flag on e_A(Fe)
39- 42 F4.2 [-] A(FeII) ? Fe abundance from FeII lines
46- 49 F4.2 [-] e_A(FeII) ? uncertainty on the abundance from FeII lines
54- 57 F4.2 [-] A(C) C abundance, A(C)
58 A1 --- u_A(C) Uncertainty flag on A(C)
63- 67 F5.2 [-] 3DcorC 3D-correction on the C abundance
71- 74 F4.2 [-] A(Mg) ? Mg abundance
77- 80 F4.2 [-] e_A(Mg) ? uncertainty on the Mg abundance
84- 87 F4.2 [-] A(Si) ? Si abundance
92- 95 F4.2 [-] A(CaK) Ca abundance from the CaII-K line
96 A1 --- u_A(CaK) Uncertainty flag on A(CaK)
99-102 F4.2 [-] A(Ca) ? Ca abundance from CaI lines
105-108 F4.2 [-] e_A(Ca) ? uncertainty on the CaI abundance
113-116 F4.2 [-] A(Ti) ? Ti abundance
119-122 F4.2 [-] e_A(Ti) ? uncertainty on the Ti abundance
128-131 F4.2 [-] A(Mn) ? Mn abundance
135-138 F4.2 [-] e_A(Mn) ? uncertainty on the Mn abundance
141 A1 --- l_A(Sr) Limit flag on A(Sr)
142-146 F5.2 [-] A(Sr) ? Sr abundance
147 A1 --- u_A(Sr) Uncertainty flag on A(Sr)
149 A1 --- l_A(Ba) Limit flag on A(Ba)
150-154 F5.2 [-] A(Ba) Ba abundance
155 A1 --- u_A(Ba) Uncertainty flag on A(Ba)
157-160 A4 --- --- [SDSS]
162-180 A19 --- SDSS SDSS name of the star (JHHMMSS.ss+DDMMSS.s)
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Acknowledgements:
Elisabetta Caffau, Elisabetta.Caffau(at)obspm.fr
(End) Patricia Vannier [CDS] 13-Jun-2018