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 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 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