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J/MNRAS/463/696     M67 solar twins chemical compositions    (Liu+, 2016)

The chemical compositions of solar twins in the open cluster M67. Liu F., Asplund M., Yong D., Melendez J., Ramirez I., Karakas A.I., Carlos M., Marino A.F. <Mon. Not. R. Astron. Soc., 463, 696-704 (2016)> =2016MNRAS.463..696L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, G-type ; Equivalent widths Keywords: stars: abundances - stars: atmospheres - open clusters and associations: individual: NGC 2682 (M67) Abstract: Stars in open clusters are expected to share an identical abundance pattern. Establishing the level of chemical homogeneity in a given open cluster deserves further study as it is the basis of the concept of chemical tagging to unravel the history of the Milky Way. M67 is particularly interesting given its solar metallicity and age as well as being a dense cluster environment. We conducted a strictly line-by-line differential chemical abundance analysis of two solar twins in M67: M67-1194 and M67-1315. Stellar atmospheric parameters and elemental abundances were obtained with high precision using Keck/High Resolution Echelle Spectrometer spectra. M67-1194 is essentially identical to the Sun in terms of its stellar parameters. M67-1315 is warmer than M67-1194 by ~=150K as well as slightly more metal-poor than M67-1194 by ~=0.05dex. M67-1194 is also found to have identical chemical composition to the Sun, confirming its solar-twin nature. The abundance ratios [X/Fe] of M67-1315 are similar to the solar abundances for elements with atomic number Z≤30, while most neutron-capture elements are enriched by ~=0.05dex, which might be attributed to enrichment from a mixture of asymptotic giant branch ejecta and r-process material. The distinct chemical abundances for the neutron-capture elements in M67-1315 and the lower metallicity of this star compared to M67-1194, indicate that the stars in M67 are likely not chemically homogeneous. This poses a challenge for the concept of chemical tagging since it is based on the assumption of stars forming in the same star-forming aggregate. Description: We observed two solar-type members in M67: M67-1194 and M67-1315. One of which (M67-1194) has been studied previously by Oenehag et al. (2011A&A...528A..85O). We obtained high resolution (R=λ/Δλ=50000), high signal-to-noise ratio (SNR) spectra with the 0.86" slit of the High Resolution Echelle Spectrometer (HIRES) on the 10 m Keck I telescope during January 24-25, 2015. Objects: ----------------------------------------------------------------- RA (2000) DE Designation(s) ----------------------------------------------------------------- 08 51 00.807 +11 48 52.76 M67-1194 = Cl* NGC 2682 YBP 1194 08 51 58.774 +11 50 02.49 M67-1462 = Cl* NGC 2682 SAND 1462 ----------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file tablea1.dat 60 391 Atomic line data, as well as the EW measurements, adopted for our analysis
Byte-by-byte Description of file: tablea1.dat
Bytes Format Units Label Explanations
1- 8 F8.3 0.1nm lambda Wavelength (Angstrom) 14- 17 F4.1 --- Species Species 22- 25 F4.2 eV EP Lower excitation potential (eV) 29- 33 F5.2 [-] loggf Oscillator strength 37- 41 F5.1 0.1pm EW1 Asteroid Hebe equivalent width for Sun values 46- 50 F5.1 0.1pm EW2 M67-1194 equivalent width 56- 60 F5.1 0.1pm EW3 M67-1315 equivalent width
History: From electronic version of the journal
(End) Patricia Vannier [CDS] 30-Apr-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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