J/AJ/128/2402 Extremely metal-poor star candidates abundances (Lai+, 2004)
Abundances of extremely metal-poor star candidates.
Lai D.K., Bolte M., Johnson J.A., Lucatello S.
<Astron. J., 128, 2402-2419 (2004)>
=2004AJ....128.2402L 2004AJ....128.2402L
ADC_Keywords: Stars, population II ; Stars, metal-deficient ;
Abundances, peculiar
Keywords: instrumentation: spectrographs - stars: abundances -
stars: Population II
Abstract:
We present chemical abundances for 110 stars identified in
objective-prism surveys as candidates for being very metal-poor. The
abundances are derived from high-S/N, intermediate-resolution spectra
obtained with the Keck Observatory Echellette Spectrograph and Imager
(ESI). An additional 25 stars with well-determined abundances ranging
from [Fe/H]=-1.5 to -3.2 were observed and the results used to help
calibrate our analysis and determine the accuracy of our abundance
determinations. Abundances for the program stars were measured for Fe,
Mg, Ca, Ti, Cr, and Ba with an accuracy of approximately 0.3dex.
Fifty-three of the stars in our sample have [Fe/H]≤-2, 22 have
[Fe/H]≤-2.5, and 13 have [Fe/H]≤-2.9. Surprisingly, approximately
one-third of the sample is relatively metal-rich, with [Fe/H]>-1.5. In
addition to identifying a number of extremely metal-poor stars, this
study also shows that moderate-resolution spectra obtained with the
Keck ESI yield relatively accurate abundances for stars as faint as
V=14 with modest exposure time (∼20 minutes). This capability will
prove useful if the so-far elusive stars at [Fe/H]←4 turn out to be
mostly fainter than V=15.
Description:
Over several runs and 4 years, we used ESI to obtain spectra of 110
stars from the lists of Beers et al. (1992, Cat. J/AJ/103/1987) and
Norris et al. (1999, Cat. J/ApJS/123/639).
We also observed 25 metal-poor stars for which high spectral
resolution, high-quality studies exist in the literature to evaluate
the suitability of ESI spectra for measuring chemical abundances.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 55 137 Star positions (from Simbad)
table2.dat 75 112 Program star photometry
ew.dat 310 135 Equivalent widths measurement of MgI, CaI, TiII,
CrI, BaII and FeI (tables 3-6 of the paper)
table7.dat 28 48 Excitation potentials and oscillator strengths
table8.dat 51 109 Program star atmospheres and radial velocities
table9.dat 50 135 Line Information
refs.dat 153 22 References
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See also:
J/AJ/90/2089 : Stars of very low metal abundance (Beers+, 1985)
J/AJ/103/1987 : Stars of very low metal abundance (Beers+, 1992)
J/ApJS/123/639 : UBV photometry of metal-weak candidates (Norris+, 1999)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star name
14- 15 I2 h RAh Simbad right ascension (J2000)
17- 18 I2 min RAm Simbad right ascension (J2000)
20- 23 F4.1 s RAs Simbad right ascension (J2000)
25 A1 --- DE- Simbad declination sign (J2000)
26- 27 I2 deg DEd Simbad declination (J2000)
29- 30 I2 arcmin DEm Simbad declination (J2000)
32- 33 I2 arcsec DEs Simbad declination (J2000)
35- 55 A21 --- SName Simbad name
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Name Star identification
14 A1 --- f_Name [d*] Flag on Name (1)
16- 20 F5.2 mag Vmag ? The V-band magnitude
22- 25 F4.2 mag B-V ? The (B-V) color index
27- 30 F4.2 mag E(B-V) ? The (B-V) color excess
32- 36 F5.3 mag b-y ? Stroemgren (b-y) color
38- 43 F6.3 mag c1 ? Stroemgren c1 index
45- 49 F5.3 mag (b-y)0 ? Intrinsic Stroemgren (b-y) color index
51- 56 F6.3 mag (c1)0 ? Intrinsic c1 index
58- 59 I2 --- r_Name Reference for Name
61- 64 I4 --- ExpTime Exposure time
66- 75 A10 "YYYY/MM/DD" Obs.Date Date of the observation
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Note (1): Flag as follows:
d = The photometry information from Allende Prieto et al.
(2000AJ....120.1516A 2000AJ....120.1516A) was derived directly into dereddened
colors from R∼2000 spectra, and therefore we do not apply a
reddening correction to any of these stars.
* = These spectra were taken with a 1.25arcsec wide slit, and
therefore the standard calibrations do not fully apply to them.
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Byte-by-byte Description of file: ew.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star identification
14- 18 F5.1 10-13m EW4167Mg ? Mg I (4167.27) equivalent width (1)
20- 24 F5.1 10-13m EW5172Mg ? Mg I (5172.69) equivalent width (1)
26- 30 F5.1 10-13m EW5183Mg ? Mg I (5183.61) equivalent width (1)
32- 36 F5.1 10-13m EW5528Mg ? Mg I (5528.41) equivalent width (1)
38- 42 F5.1 10-13m EW4425Ca ? Ca I (4425.44) equivalent width (1)
44- 48 F5.1 10-13m EW5586Ca ? Ca I (5586.76) equivalent width (1)
50- 54 F5.1 10-13m EW6122Ca ? Ca I (6122.22) equivalent width (1)
56- 60 F5.1 10-13m EW6162Ca ? Ca I (6162.18) equivalent width (1)
62- 66 F5.1 10-13m EW6439Ca ? Ca I (6439.08) equivalent width (1)
68- 72 F5.1 10-13m EW6471Ca ? Ca I (6471.66) equivalent width (1)
74- 78 F5.1 10-13m EW6717Ca ? Ca I (6717.68) equivalent width (1)
80- 84 F5.1 10-13m EW4028Ti ? Ti II (4028.34) equivalent width (1)
86- 90 F5.1 10-13m EW4395Ti ? Ti II (4395.04) equivalent width (1)
92- 95 F4.1 10-13m EW4399Ti ? Ti II (4399.77) equivalent width (1)
97-101 F5.1 10-13m EW4443Ti ? Ti II (4443.81) equivalent width (1)
103-107 F5.1 10-13m EW4468Ti ? Ti II (4468.50) equivalent width (1)
109-113 F5.1 10-13m EW4563Ti ? Ti II (4563.76) equivalent width (1)
115-119 F5.1 10-13m EW4571Ti ? Ti II (4571.98) equivalent width (1)
121-125 F5.1 10-13m EW4589Ti ? Ti II (4589.95) equivalent width (1)
127-131 F5.1 10-13m EW5336Ti ? Ti II (5336.79) equivalent width (1)
133-137 F5.1 10-13m EW5345Cr ? Cr I (5345.80) equivalent width (1)
139-143 F5.1 10-13m EW4554Ba ? Ba II (4554.04) equivalent width (1)
145-149 F5.1 10-13m EW6141Ba ? Ba II (6141.75) equivalent width (1)
151-155 F5.1 10-13m EW4045Fe ? Fe I (4045.82) equivalent width (1)
157-161 F5.1 10-13m EW4071Fe ? Fe I (4071.74) equivalent width (1)
163-167 F5.1 10-13m EW4383Fe ? Fe I (4383.55) equivalent width (1)
169-173 F5.1 10-13m EW4404Fe ? Fe I (4404.76) equivalent width (1)
175-179 F5.1 10-13m EW4442Fe ? Fe I (4442.35) equivalent width (1)
181-185 F5.1 10-13m EW4919Fe ? Fe I (4919.00) equivalent width (1)
187-191 F5.1 10-13m EW5068Fe ? Fe I (5068.77) equivalent width (1)
193-197 F5.1 10-13m EW5074Fe ? Fe I (5074.75) equivalent width (1)
199-203 F5.1 10-13m EW5133Fe ? Fe I (5133.69) equivalent width (1)
205-208 F4.1 10-13m EW5216Fe ? Fe I (5216.28) equivalent width (1)
210-214 F5.1 10-13m EW5232Fe ? Fe I (5232.95) equivalent width (1)
216-220 F5.1 10-13m EW5302Fe ? Fe I (5302.30) equivalent width (1)
222-226 F5.1 10-13m EW5324Fe ? Fe I (5324.19) equivalent width (1)
228-232 F5.1 10-13m EW5383Fe ? Fe I (5383.38) equivalent width (1)
234-238 F5.1 10-13m EW5393Fe ? Fe I (5393.17) equivalent width (1)
240-244 F5.1 10-13m EW5405Fe ? Fe I (5405.78) equivalent width (1)
246-250 F5.1 10-13m EW5434Fe ? Fe I (5434.53) equivalent width (1)
252-256 F5.1 10-13m EW5586Fe ? Fe I (5586.77) equivalent width (1)
258-262 F5.1 10-13m EW6065Fe ? Fe I (6065.49) equivalent width (1)
264-268 F5.1 10-13m EW6230Fe ? Fe I (6230.73) equivalent width (1)
270-274 F5.1 10-13m EW6252Fe ? Fe I (6252.56) equivalent width (1)
276-280 F5.1 10-13m EW6393Fe ? Fe I (6393.61) equivalent width (1)
282-286 F5.1 10-13m EW6411Fe ? Fe I (6411.65) equivalent width (1)
288-292 F5.1 10-13m EW6430Fe ? Fe I (6430.85) equivalent width (1)
294-298 F5.1 10-13m EW6609Fe ? Fe I (6609.11) equivalent width (1)
300-304 F5.1 10-13m EW6677Fe ? Fe I (6677.99) equivalent width (1)
306-310 F5.1 10-13m EW6750Fe ? Fe I (6750.15) equivalent width (1)
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Note (1): In units of milliAngstroms.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ion Species name and ionisation stage
7- 13 F7.2 0.1nm Lambda Wavelength in Angstroms
15- 20 F6.3 [-] log(gf) Logarithm of the oscillator strength
22- 25 F4.2 eV ExPot Excitation potential
27- 28 I2 --- r_log(gf) Reference on log(gf)
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star identification
14 A1 --- f_Name [d*] Flag on Name (1)
16- 19 I4 K Teff ? Effective temperature
21- 24 F4.2 [cm/s2] log(g) ? Logarithm of the surface gravity
26- 30 F5.2 [Sun] [M/H] ? Logarithm of the metallicity
32- 35 I4 K Teff0 Reddening-corrected effective temperature
37- 40 F4.2 [cm/s2] log(g)0 Logarithm of the reddening-corrected
surface gravity
42- 46 F5.2 [Sun] [M/H]0 Logarithm of the reddening-corrected
metallicity
48- 51 I4 km/s RV Radial velocity
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Note (1): Flags as follows:
d = These objects have derived photometry from Allende Prieto et al.
(2000AJ....120.1516A 2000AJ....120.1516A), where only intrinsic (B-V)0 color is given.
* = The photometry without reddening correction falls out of our
range to derive an atmosphere.
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star identification
14- 15 I2 --- NFe ? Number of Fe lines measured
17- 20 F4.2 [Sun] sigmaFe ? Standard deviation of Fe
22 I1 --- NMg ? Number of Mg lines
24- 27 F4.2 [Sun] sigmaMg ? Standard deviation of Mg
29 I1 --- NCa ? Number of Ca lines
31- 34 F4.2 [Sun] sigmaCa ? Standard deviation of Ca
36 I1 --- NTiII ? Number of Ti II lines
38- 43 F6.2 [Sun] sigmaTiII ? Standard deviation of Ti II
45 I1 --- NBaII ? Number of Ba II lines
47- 50 F4.2 [Sun] sigmaBaII ? Standard deviation of Ba II
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 22 A19 --- BibCode BibCode
24- 40 A17 --- Aut Authors name
42-153 A112 --- Com Comments
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 23-Jan-2007