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J/A+A/548/A34    Abundances of carbon-enhanced metal-poor stars  (Allen+, 2012)

Elemental abundances and classification of carbon-enhanced metal-poor stars. Allen D.M., Ryan S.G., Rossi S., Beers T.C., Tsangarides S.A. <Astron. Astrophys. 548, A34 (2012)> =2012A&A...548A..34A
ADC_Keywords: Stars, carbon ; Stars, metal-deficient ; Abundances Keywords: stars: abundances - stars: atmospheres - stars: chemically peculiar - stars: carbon Abstract: We present a detailed study of Carbon-Enhanced Metal-Poor (CEMP) stars, based on high-resolution spectroscopic observations of a sample of 18 stars. The stellar spectra for this sample were obtained at the 4.2m William Herschel Telescope (WHT) in 2001 and 2002, using the Utrecht Echelle Spectrograph (UES), at a resolving power R∼52000 and S/N∼40, covering the wavelength range λ-λ3700-5700Å. The atmospheric parameters determined for this sample indicate temperatures ranging from 4750K to 7100K, log g from 1.5 to 4.3, and metallicities -3.0≤[Fe/H]≤-1.7. Elemental abundances for C, Na, Mg, Sc, Ti, Cr, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, Gd, Dy are determined. Abundances for an additional 109 stars were taken from the literature and combined with the data of our sample. The literature sample reveals a lack of reliable abundance estimates for species that might be associated with the r-process elements for about 67% of CEMP stars, preventing a complete understanding of this class of stars, since [Ba/Eu] ratios are used to classify them. Although eight stars in our observed sample are also found in the literature sample, Eu abundances or limits are determined for four of these stars for the first time. From the observed correlations between C, Ba, and Eu, we argue that the CEMP-r/s class has the same astronomical origin as CEMP-s stars, highlighting the need for a more complete understanding of Eu production. Description: Abundances for 18 CEMP stars are presented: BS 15621-047, BS 16033-081, BS 16077-077, BS 16082-129, BS 16543-097, BS 16929-005, CS 22949-008, CS 29503-010, CS 29512-073, CS 29526-110, CS 29528-028, CS 31070-073, BS 16080-175, BS 17436-058, CS 22183-015, CS 22887-048, CS 22898-027, CS 29502-092. Our results were compared to data of 109 stars from the literature. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 148 28 Colours and magnitudes of our program stars before dereddening table2.dat 56 2316 Iron lines for DMA subsample table5.dat 56 5302 All abundances for SAT subsample table7.dat 76 1128 Other elemental abundances for DMA subsample
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 A3 --- Sample Subsample: DMA (Dinah M. Allen) or SAT (Stelios A. Tsangarides) 5- 16 A12 --- Star Star name 17 A1 --- n_Star [*] position and magnitude added at CDS (concerns HD 140283) 18- 19 I2 h RAh Right ascension (J2000) 21- 22 I2 min RAm Right ascension (J2000) 24- 27 F4.1 s RAs Right ascension (J2000) 29 A1 --- DE- Declination sign (J2000) 30- 31 I2 deg DEd Declination (J2000) 33- 34 I2 arcmin DEm Declination (J2000) 36- 37 I2 arcsec DEs Declination (J2000) 39- 44 F6.3 mag Vmag ? V magnitude 46- 50 F5.3 mag E(B-V) ? Interstellar reddening 52- 56 F5.3 mag AV ? Absorption in V band 58- 61 F4.3 mag e_AV ? rms uncertainty on AV 63- 67 F5.3 mag B-V ? B-V colour index 68 A1 --- n_B-V [X] X for value not used 70- 74 F5.3 mag V-R ? V-R colour index 76- 80 F5.3 mag V-I ? V-I colour index 82- 87 F6.3 mag Jmag ? J magnitude 89- 92 F4.3 mag e_Jmag ? rms uncertainty on Jmag 94- 99 F6.3 mag Hmag ? H magnitude 101-104 F4.3 mag e_Hmag ? rms uncertainty on Hmag 106-111 F6.3 mag Ksmag ? Ks magnitude 113-116 F4.3 mag e_Ksmag ? rms uncertainty on Ksmag 118-122 F5.1 deg GLON ? Galactic longitude 124-128 F5.1 deg GLAT ? Galactic latitude 130-132 I3 --- S/N ? Signal-to-noise ratio of the high-resolution spectra around λ4500Å 134-148 A15 --- Note ? Notes
Byte-by-byte Description of file: table2.dat table5.dat
Bytes Format Units Label Explanations
1- 12 A12 --- Star Star name 14- 18 A5 --- Ion Element code and ionization state 21- 29 F9.4 0.1nm lambda Wavelength of the line 32- 36 F5.3 eV EP Lower excitation potential 39- 44 F6.3 --- loggf Logarithm of oscillator strength 47 I1 --- r_loggf [1/9] References for oscillator strength (1) 49 A1 --- l_EW Upper limit flag on EW 50- 55 F6.2 0.1pm EW ?=- Equivalent width 56 A1 --- n_EW [s] s indicates spectrum synthesis
Note (1): References as follows: 1 = Fuhr et al. (1988, Cat. VI/72) 2 = Kurucz & Peytremann (1975, SAO Special Report 362 (Cambridge: Smithsonian Institution)) 3 = NIST 4 = Ryan & Lambert (1995AJ....109.2068R) 5 = Thevenin (1989A&AS...77..137T) 6 = Kurucz (1989, priv. comm.) 7 = Experimental sources 8 = Fuhr & Wiese (2006, J. Phys. Chem. Ref. D., 35, 4) 9 = Kurucz, R. 1994, CD 22
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
1- 12 A12 --- Star Star name 15- 19 A5 --- Ion Element code and ionization state 23- 30 A8 0.1nm lambda Wavelength of the line 35- 39 F5.3 eV EP ?=- Lower excitation potential 44- 49 F6.3 --- loggf ?=- Logarithm of oscillator strength 53- 54 I2 --- r_loggf ?=- References for oscillator strength (1) 58- 60 I3 0.1pm EW ?=- Equivalent width for the star 61 A1 --- n_EW [s] s indicates spectrum synthesis 64- 68 F5.2 --- logEps ?=- Average of logε= log(Nx/NH) + 12 72- 76 F5.2 --- [X/Fe] ?=- Average of the overabundance of the element X relative to Fe
Note (1): References as follows: 1 = NIST 2 = Fuhrmann et al. (1995A&A...301..492F) 3 = Martin et al. (1988, Cat. VI/72) 4 = Bielski (1975, JQSRT, 15, 463) 5 = Biemont & Godefroid (1980, A&A, 84, 361) 6 = Gratton & Sneden (1994, Cat. J/A+A/287/927) 7 = Hannaford et al. (1982ApJ...261..736H) 8 = Hannaford & Lowe (1983, Opt. Eng., 22, 532) 9 = Biemont et al. (1981ApJ...248..867B) 10 = Thevenin (1989A&AS...77..137T) 11 = Sneden et al. (1996ApJ...467..819S) 12 = McWilliam (1998AJ....115.1640M) 13 = Lawler et al. (2001ApJ...556..452L) 14 = Palmeri et al. (2000, Physica Scripta, 61, 323) 15 = Hartog et al. (2003ApJS..148..543D) 16 = Maier & Whaling (1977, JQSRT, 18, 501) 17 = Biemont et al. (1989A&A...222..307B) 18 = Lawler et al. (2001ApJ...563.1075L) 19 = Corliss & Bozman (1962, Experimental Transition Probabilities for Spectral Lines of Seventy Elements, NBS Monograph 32 (Washington: GPO)) 20 = VALD data-base (http://vald.astro.univie.ac.at/~vald/php/vald.php) 21 = Bergstrom et al. (1988, A&A, 192, 337) 22 = average of Kusz (1992A&AS...92..517K) and Biemont & Lowe (1993A&A...273..665B)
Acknowledgements: Dinah Moreira Allen, dimallen at astro.iag.usp.br
(End) Patricia Vannier [CDS] 29-Nov-2012
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