J/ApJ/742/54 CASH project II. 14 extremely metal-poor stars (Hollek+, 2011)
The Chemical Abundances of Stars in the Halo (CASH) project.
II. A sample of 14 extremely metal-poor stars.
Hollek J.K., Frebel A., Roederer I.U., Sneden C., Shetrone M., Beers T.C.,
Kang S.-J., Thom C.
<Astrophys. J., 742, 54 (2011)>
=2011ApJ...742...54H 2011ApJ...742...54H
ADC_Keywords: Equivalent widths ; Abundances ; Stars, halo ;
Stars, metal-deficient
Keywords: Galaxy: halo - methods: data analysis - stars: abundances -
stars: atmospheres - stars: Population II
Abstract:
We present a comprehensive abundance analysis of 20 elements for 16
new low-metallicity stars from the Chemical Abundances of Stars in the
Halo (CASH) project. The abundances have been derived from both
Hobby-Eberly Telescope High Resolution Spectrograph snapshot spectra
(R∼15000) and corresponding high-resolution (R∼35000) Magellan Inamori
Kyocera Echelle spectra. The stars span a metallicity range from
[Fe/H] from -2.9 to -3.9, including four new stars with [Fe/H]←3.7.
We find four stars to be carbon-enhanced metal-poor (CEMP) stars,
confirming the trend of increasing [C/Fe] abundance ratios with
decreasing metallicity. Two of these objects can be classified as
CEMP-no stars, adding to the growing number of these objects at
[Fe/H]←3. We also find four neutron-capture-enhanced stars in the
sample, one of which has [Eu/Fe] of 0.8 with clear r-process
signatures. These pilot sample stars are the most metal-poor
([Fe/H]≲-3.0) of the brightest stars included in CASH and are used to
calibrate a newly developed, automated stellar parameter and abundance
determination pipeline. This code will be used for the entire ∼500
star CASH snapshot sample. We find that the pipeline results are
statistically identical for snapshot spectra when compared to a
traditional, manual analysis from a high-resolution spectrum.
Description:
The stars of the pilot study were chosen from the Hamburg/ESO Bright
Metal-Poor Sample (BMPS; Frebel et al. 2006, Cat. J/ApJ/652/1585) of
the Hamburg/ESO objective-prism plate Survey (HES; Christlieb et al.
2001A&A...366..898C 2001A&A...366..898C).
The snapshot spectra for the Chemical Abundances of Stars in the Halo
(CASH) project were obtained using the fiber-fed High Resolution
Spectrograph (HRS) on the Hobby-Eberly Telescope (HET) at McDonald
Observatory. High-resolution spectra for 21 stars were obtained using
the MIKE instrument on the Magellan-Clay Telescope at Las Campanas
Observatory (See table 1).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 74 39 Observations (21 stars)
table2.dat 43 6288 Equivalent widths (21 stars)
table5.dat 55 21 Stellar parameters
table6.dat 476 20 Abundances
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See also:
J/MNRAS/412/843 : SAGA extremely metal-poor stars (Suda+, 2011)
J/A+A/530/A15 : Abundances of 94 stars (Nissen+, 2011)
J/ApJ/711/573 : Detailed abundances in a halo stellar stream (Roederer+, 2010)
J/A+A/501/519 : Extremely metal-poor stars abundances (Bonifacio+, 2009)
J/ApJ/706/1095 : Chemical compositions of 26 outer halo stars (Zhang+, 2009)
J/A+A/490/769 : Yields from extremely metal-poor stars (Campbell+, 2008)
J/ApJ/679/1549 : Spectroscopy of CS 17435-00532. Paper I. (Roederer+, 2008)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
J/AJ/132/137 : Abundances of extremely metal-poor carbon stars (Cohen+, 2006)
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/AJ/130/2804 : Carbon abundances in metal-poor stars (Rossi+, 2005)
J/A+A/415/993 : FeII, ZNI and SI abundances on halo stars (Nissen+, 2004)
J/A+A/425/671 : Equivalent widths of 10 metal-poor halo stars (Bai+, 2004)
J/AJ/128/2402 : Extremely metal-poor star candidates abundances (Lai+, 2004)
J/ApJS/155/651 : Evolution of extremely metal-poor stars (Herwig+, 2004)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/A+A/403/1105 : Extremely metal-poor giants EWs (Francois+, 2003)
J/A+AS/141/491 : Chemical composition of halo and disk stars (Nissen+, 2000)
J/AJ/120/1841 : Abundances & Kinematics of Halo & Disk Stars (Fulbright 2000)
J/A+A/354/169 : Metal-poor field stars abundances (Gratton+, 2000)
J/AJ/90/2089 : Stars of very low metal abundance. I (Beers+, 1985)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Star Star identification (G1)(1)
14- 21 A8 --- Tel Telescope (HET or Magellan)
23- 33 A11 "YYYY/MMM/DD" Date UT date of observation
34 A1 --- f_Date [d] d = contaminated (2)
36- 37 I2 h RAh Hour of right ascension (J2000)
39- 40 I2 min RAm Minute of right ascension (J2000)
42- 45 F4.1 s RAs Second of right ascension (J2000)
47 A1 --- DE- Sign of declination (J2000)
48- 49 I2 deg DEd Degree of declination (J2000)
51- 52 I2 arcmin DEm Arcminute of declination (J2000)
54- 55 I2 arcsec DEs Arcsecond of declination (J2000)
57- 60 I4 s Exp ? Exposure time
62- 64 I3 --- S/N ? Signal to noise ratio at 5180Å
66 A1 --- f_S/N [a] a = S/N for combined HET spectra
68- 74 F7.2 km/s RV ? Radial velocity (3)
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Note (1): BPS CS 22873-0166 and BPS CS 22873-0200 have inverted coordinates in
the published paper; positions have been fixed at CDS.
Note (2): Sky contamination in spectrum, excluded from this analysis.
Note (3): Radial velocities were computed by cross-correlating the echelle
order containing the Mg b triplet against another metal-poor giant
observed with the same instrumental setup. Typical uncertainties were
2-3km/s for a single observation.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Star Star name (G1)
14- 17 F4.1 --- Ion Ion identification (1)
19- 25 F7.2 0.1nm lambda Wavelength λ (Å)
27- 30 F4.2 eV ExPot Excitation potential
32- 37 F6.3 [-] log(gf) Log of the oscillator strength
39- 43 F5.1 0.1pm EW Equivalent width (mÅ)
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Note (1): We list the ionization state of each element where .0 indicates a
neutral species and .1 indicates a singly-ionized species.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Star Star name (G1)
14- 17 I4 K Teff Effective temperature from Magellan/MIKE
19- 22 F4.2 [cm/s2] logg Surface gravity from Magellan/MIKE
24- 27 F4.2 km/s Vt Microturbulent velocity from Magellan/MIKE
29- 33 F5.2 [Sun] [Fe/H] Metallicity from Magellan/MIKE
35- 38 I4 K Teff2 ? Effective temperature from HET/HRS
40- 43 F4.2 [cm/s2] logg2 ? Surface gravity from HET/HRS
45- 48 F4.2 km/s Vt2 ? Microturbulent velocity from HET/HRS
50- 54 F5.2 [Sun] [Fe/H]2 ? Metallicity from HET/HRS
55 A1 --- f_[Fe/H]2 [a] a = sky contamination in this spectrum
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Star Star name (G1)
14- 18 F5.2 [Sun] [Fe/H] Abundance of [Fe/H](MIKE)
20 A1 --- l_Li1 Limit flag on Li1
21- 24 F4.2 [-] Li1 logε(LiI)(MIKE)
26- 29 F4.2 [-] e_Li1 Uncertainty in Li1
31- 34 F4.2 [-] C logε(C)(MIKE)
36- 39 F4.2 [-] e_C Uncertainty in C
41- 45 F5.2 [Sun] [C/Fe] Abundance of [C/Fe](MIKE)
47- 50 F4.2 [-] Mg1 logε(MgI)(MIKE)
52- 55 F4.2 [-] e_Mg1 Uncertainty in Mg1
57- 60 F4.2 [Sun] [Mg/Fe] Abundance of [Mg/Fe](MIKE)
62 I1 --- o_Mg1 Number of MgI lines used in abundance
64- 67 F4.2 [-] Al1 ? logε(AlI)(MIKE)
69- 72 F4.2 [-] e_Al1 ? Uncertainty in Al1
74- 78 F5.2 [Sun] [Al/Fe] ? Abundance of [Al/Fe](MIKE)
80 I1 --- o_Al1 ? Number of AlI lines used in abundance
82- 85 F4.2 [-] Si1 ? logε(SiI)(MIKE)
87- 90 F4.2 [-] e_Si1 ? Uncertainty in Si1
92- 95 F4.2 [Sun] [Si/Fe] ? Abundance of [Si/Fe](MIKE)
97 I1 --- o_Si1 Number of SiI lines used in abundance
99-102 F4.2 [-] Ca1 logε(CaI)(MIKE)
104-107 F4.2 [-] e_Ca1 Uncertainty in Ca1
109-112 F4.2 [Sun] [Ca/Fe] Abundance of [Ca/Fe](MIKE)
114-115 I2 --- o_Ca1 Number of CaI lines used in abundance
117-121 F5.2 [-] Sc2 logε(ScII)(MIKE)
123-126 F4.2 [-] e_Sc2 Uncertainty in Sc2
128-132 F5.2 [Sun] [Sc/Fe] Abundance of [Sc/Fe](MIKE)
134-135 I2 --- o_Sc2 Number of ScII lines used in abundance
137-140 F4.2 [-] Ti1 logε(TiI)(MIKE)
142-145 F4.2 [-] e_Ti1 Uncertainty in Ti1
147-151 F5.2 [Sun] [Ti1/Fe] Abundance of [Ti1/Fe](MIKE)
153-154 I2 --- o_Ti1 Number of TiI lines used in abundance
156-159 F4.2 [-] Ti2 logε(TiII)(MIKE)
161-164 F4.2 [-] e_Ti2 Uncertainty in Ti2
166-170 F5.2 [Sun] [Ti2/Fe] Abundance of [Ti2/Fe](MIKE)
172-173 I2 --- o_Ti2 Number of TiII lines used in abundance
175-178 F4.2 [-] Cr1 ? logε(CrI)(MIKE)
180-183 F4.2 [-] e_Cr1 ? Uncertainty in Cr1
185-189 F5.2 [Sun] [Cr1/Fe] ? Abundance of [Cr1/Fe](MIKE)
191-192 I2 --- o_Cr1 ? Number of CrI lines used in abundance
194-197 F4.2 [-] Cr2 ? logε(CrII)_MIEK
199-202 F4.2 [-] e_Cr2 ? Uncertainty in Cr2
204-208 F5.2 [Sun] [Cr2/Fe] ? Abundance of [Cr2/Fe](MIKE)
210 I1 --- o_Cr2 Number of CrII lines used in abundance
212-215 F4.2 [-] Mn1 ? logε(MnI)(MIKE)
217-220 F4.2 [-] e_Mn1 ? Uncertainty in Mn1
222-226 F5.2 [Sun] [Mn/Fe] ? Abundance of [Mn/Fe](MIKE)
228 I1 --- o_Mn1 ? Number of MnI lines used in abundance
230-233 F4.2 [-] Co1 logε(CoI)(MIKE)
235-238 F4.2 [-] e_Co1 Uncertainty in Co1
240-244 F5.2 [Sun] [Co/Fe] Abundance of [Co/Fe](MIKE)
246-247 I2 --- o_Co1 Number of CoI lines used in abundance
249-252 F4.2 [-] Ni1 logε(NiI)(MIKE)
254-257 F4.2 [-] e_Ni1 Uncertainty in Ni1
259-263 F5.2 [Sun] [Ni/Fe] Abundance of [Ni/Fe](MIKE)
265-266 I2 --- o_Ni1 Number of NiI lines used in abundance
268 A1 --- l_Zn1 Limit flag on Zn1
269-272 F4.2 [-] Zn1 logε(ZnI)(MIKE)
274 A1 --- leZn1 Limit flag on eZn1
275-278 F4.2 [-] e_Zn1 Uncertainty in Zn1
280-283 F4.2 [Sun] [Zn/Fe] Abundance of [Zn/Fe](MIKE)
285 I1 --- o_Zn1 Number of ZnI lines used in abundance
287-291 F5.2 [-] Sr2 logε(SrII)(MIKE)
293-296 F4.2 [-] e_Sr2 Uncertainty in Sr2
298-302 F5.2 [Sun] [Sr/Fe] Abundance of [Sr/Fe](MIKE)
304 I1 --- o_Sr2 Number of SrII lines used in abundance
306 A1 --- l_Y2 Limit flag on Y2
307-311 F5.2 [-] Y2 logε(Y.II)(MIKE)
313 A1 --- l_eY2 Limit flag on eY2
314-318 F5.2 [-] eY2 Uncertainty in Y2
320-323 F4.2 [Sun] [Y/Fe] Abundance of [Y/Fe](MIKE)
325 I1 --- o_Y2 Number of Y.II lines used in abundance
327 A1 --- l_Zr2 Limit flag on Zr2
328-332 F5.2 [-] Zr2 logε(ZrII)(MIKE)
334-337 F4.2 [-] e_Zr2 Uncertainty in Zr2
339 A1 --- l_[Zr/Fe] Limit flag on [Zr2/Fe]
340-344 F5.2 [Sun] [Zr/Fe] Abundance of [Zr/Fe](MIKE)
346 I1 --- o_Zr2 Number of ZrII lines used in abundance
348-352 F5.2 [-] Ba2 logε(BaII)(MIKE)
354-358 F5.2 [-] [Ba2/Fe] Abundance of [Ba/Fe](MIKE)
360-363 F4.2 [Sun] e_Ba2 Uncertainty in Ba2
365 I1 --- o_Ba2 Number of BaII lines used in abundance
367 A1 --- l_La2 Limit flag on La2
368-372 F5.2 [-] La2 logε(LaII)(MIKE)
374-377 F4.2 [-] e_La2 Uncertainty in La2
379 A1 --- l_[La/Fe] Limit flag on [La/Fe]
380-384 F5.2 [Sun] [La/Fe] Abundance of [La/Fe](MIKE)
386 I1 --- o_La2 Number of LaII lines used in abundance
388 A1 --- l_Eu2 Limit flag on Eu2
389-393 F5.2 [-] Eu2 logε(EuII)(MIKE)
395-398 F4.2 [-] e_Eu2 Uncertainty in Eu2
400 A1 --- l_[Eu/Fe] Limit flag on [Eu/Fe]
401-405 F5.2 [Sun] [Eu/Fe] Abundance of [Eu/Fe](MIKE)
407 I1 --- o_Eu2 Number of EuII lines used in abundance
409-413 F5.2 [Sun] [Fe/H]H ? Abundance of [Fe/H](HRS)
415-419 F5.2 [Sun] [Cg/Fe]H ? Abundance of [Cg/Fe](HRS)
421-424 F4.2 [Sun] [Mg/Fe]H ? Abundance of [Mg/Fe](HRS)
426-429 F4.2 [Sun] [Ca/Fe]H ? Abundance of [Ca/Fe](HRS)
431-435 F5.2 [Sun] [Sc/Fe]H ? Abundance of [Sc/Fe](HRS)
437-440 F4.2 [Sun] [Ti/Fe]H ? Abundance of [Ti/Fe](HRS)
442-446 F5.2 [Sun] [Cr/Fe]H ? Abundance of [Cr/Fe](HRS)
448-452 F5.2 [Sun] [Mn/Fe]H ? Abundance of [Mn/Fe](HRS)
454-458 F5.2 [Sun] [Zn/Fe]H ? Abundance of [Zn/Fe](HRS)
460-464 F5.2 [Sun] [Sr/Fe]H ? Abundance of [Sr/Fe](HRS)
466-470 F5.2 [Sun] [Y/Fe]H ? Abundance of [Y/Fe](HRS)
472-476 F5.2 [Sun] [Ba/Fe]H ? Abundance of [Ba/Fe](HRS)
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Global notes:
Note (G1): Due to the low-metallicity of CD-38 245, the corresponding MIKE
spectrum shows very few absorption lines; thus, we included this star only
in the calibration of the stellar parameter offset.
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History:
From electronic version of the journal
References:
Roederer et al. Paper I. 2008ApJ...679.1549R 2008ApJ...679.1549R Cat. J/ApJ/679/1549
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 18-Apr-2013