J/ApJ/769/57 Equivalent widths of metal-poor stars (Frebel+, 2013)
Deriving stellar effective temperatures of metal-poor stars with the excitation
potential method.
Frebel A., Casey A.R., Jacobson H.R., Yu Q.
<Astrophys. J., 769, 57 (2013)>
=2013ApJ...769...57F 2013ApJ...769...57F
ADC_Keywords: Equivalent widths ; Effective temperatures ; Abundances ;
Stars, metal-deficient
Keywords: stars: abundances; stars: fundamental parameters; stars: Population II
Abstract:
It is well established that stellar effective temperatures determined
from photometry and spectroscopy yield systematically different
results. We describe a new, simple method to correct spectroscopically
derived temperatures ("excitation temperatures") of metal-poor stars
based on a literature sample with -3.3<[Fe/H]←2.5. Excitation
temperatures were determined from Fe I line abundances in
high-resolution optical spectra in the wavelength range of
∼3700-7000Å, although shorter wavelength ranges, up to
4750-6800Å, can also be employed, and compared with photometric
literature temperatures. Our adjustment scheme increases the
temperatures up to several hundred degrees for cool red giants, while
leaving the near-main-sequence stars mostly unchanged. Hence, it
brings the excitation temperatures in good agreement with
photometrically derived values. The modified temperature also
influences other stellar parameters, as the Fe I-Fe II ionization
balance is simultaneously used to determine the surface gravity, while
also forcing no abundance trend on the absorption line strengths to
obtain the microturbulent velocity. As a result of increasing the
temperature, the often too low gravities and too high microturbulent
velocities in red giants become higher and lower, respectively. Our
adjustment scheme thus continues to build on the advantage of deriving
temperatures from spectroscopy alone, independent of reddening, while
at the same time producing stellar chemical abundances that are more
straightforwardly comparable to studies based on photometrically
derived temperatures. Hence, our method may prove beneficial for
comparing different studies in the literature as well as the many
high-resolution stellar spectroscopic surveys that are or will be
carried out in the next few years.
Description:
All high S/N, high-resolution spectra were obtained with the MIKE
spectrograph on the Magellan-Clay telescope at Las Campanas
Observatory between 2009 and 2011 (R∼35000 in the blue and ∼28000 in
the red spectral range).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 108 540 Equivalent widths and metal line abundances
of stars in the calibration sample
table3.dat 63 7 Stellar parameters of the sample
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See also:
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)
J/ApJ/753/64 : Detailed abundances for 97 metal-poor stars (Ishigaki+, 2012)
J/ApJ/742/54 : CASH project II. 14 extremely metal-poor stars (Hollek+, 2011)
J/ApJ/711/573 : Detailed abundances in a halo stellar stream (Roederer+, 2010)
J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)
J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)
J/A+A/493/601 : Lithium abundances of halo dwarfs (Hosford+, 2009)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/ApJS/168/128 : UBVRcIc photometry of FHB and metal-poor stars (Beers+, 2007)
J/AJ/132/137 : Abundances of extremely metal-poor carbon stars (Cohen+, 2006)
J/A+A/440/321 : Chemical abundances in 43 metal-poor stars (Jonsell+, 2005)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/AJ/128/2402 : Extremely metal-poor star candidates abundances (Lai+, 2004)
J/A+A/425/671 : Equivalent widths of 10 metal-poor halo stars (Bai+, 2004)
J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)
J/A+A/403/1105 : Extremely metal-poor giants EWs (Francois+, 2003)
J/AJ/119/1448 : Improved properties for cool stars (Houdashelt+, 2000)
J/A+AS/131/209 : JHK(L') photometry of giant stars (Alonso+ 1998)
J/A+AS/97/951 : uvby-beta photometry of metal-poor stars (Schuster+ 1993)
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
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1- 8 F8.3 0.1nm lambda Wavelengthλ; Angstroms
10- 13 A4 --- Ion Species identifier
15- 18 F4.2 eV ExPot Excitation potential
20- 25 F6.3 [-] log(gf) ? Log of the oscillator strength
27- 32 F6.2 10-13m W(HD122563) ? Equivalent width in HD122563 (mÅ)
34- 37 F4.2 [-] e(HD122563) ? logε abundance in HD122563
39- 44 F6.2 10-13m W(HE1523-0901) ? Equivalent width in HE1523-0901 (mÅ)
46- 49 F4.2 [-] e(HE1523-0901) ? logε abundance in HE1523-0901
51- 56 F6.2 10-13m W(BD-185550) ? Equivalent width in BD-18 5550 (mÅ)
58- 61 F4.2 [-] e(BD-185550) ? logε abundance in BD-18 5550
63- 68 F6.2 10-13m W(CS22892-052) ? Equivalent width in CS22892-052 (mÅ)
70- 74 F5.2 [-] e(CS22892-052) ? logε abundance in CS22892-052
76- 81 F6.2 10-13m W(HD140283) ? Equivalent width in HD140283 (mÅ)
83- 86 F4.2 [-] e(HD140283) ? logε abundance in HD140283
88- 92 F5.2 10-13m W(CD-2417504) ? Equivalent width in CD-24 17504 (mÅ)
94- 97 F4.2 [-] e(CD-2417504) ? logε abundance in CD-24 17504
99-103 F5.2 10-13m W(G64-12) ? Equivalent width in G64-12 (mÅ)
105-108 F4.2 [-] e(G64-12) ? logε abundance in G64-12
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Star name
13- 16 I4 K Teff [4630/6420] Adopted effective temperature
18- 21 I4 K Teff2 [4644/6276]? Effective temperature from V-K
23- 26 I4 K Teffi [4380/6430] Initial determination of Teff
28- 31 F4.2 [cm/s2] loggi [0.05/4.4] Initial determination of log(g)
33- 37 F5.2 [Sun] [Fe/H]i [-3.3/-2.7] Initial determination of [Fe/H]
39- 42 F4.2 km/s Vti [1.3/2.9] Initial determination of
microturbulent velocity (Vt)
44- 47 I4 K Teffc [4612/6457] Teff after temperature correction
49- 52 F4.2 [cm/s2] loggc [0.8/4.4] log(g) after temperature correction
54- 58 F5.2 [Sun] [Fe/H]c [-3.3/-2.6] [Fe/H] after temperature correction
60- 63 F4.2 km/s Vtc [1.4/2.7] Vt after temperature correction
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 09-Dec-2014