J/A+A/627/A117 Equivalent widths for six M67 stars (Liu+, 2019)
Chemical (in)homogeneity and atomic diffusion in the open cluster M67.
Liu F., Asplund M., Yong D., Feltzing S., Dotter A., Melendez J., Ramirez I.
<Astron. Astrophys. 627, A117 (2019)>
=2019A&A...627A.117L 2019A&A...627A.117L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Populations, stellar ; Equivalent widths
Keywords: stars: abundances - stars: atmospheres - stars: evolution -
open clusters and associations: individual: NGC 2682
Abstract:
The benchmark open cluster M67 is known to have solar metallicity and
similar age as the Sun. It thus provides us a great opportunity to
study the properties of solar twins, as well as the evolution of
Sun-like stars.
Previous spectroscopic studies claimed to detect possible subtle
changes in stellar surface abundances throughout the stellar
evolutionary phase, namely the effect of atomic diffusion, in M67. In
this study we attempt to confirm and quantify the effect of atomic
diffusion, as well as to explore the level of chemical (in)homogeneity
in M67.
We presented a strictly line-by-line differential chemical abundance
analysis of two groups of stars in M67: three turn-off stars and three
sub-giants. Stellar atmospheric parameters and elemental abundances
were obtained with very high precision using the Keck/HIRES spectra.
The sub-giants in our sample show negligible abundance variations
(≤0.02dex), which implies that M67 was born chemically homogeneous.
We note there is a significant abundance difference (∼0.1-0.2dex)
between sub-giants and turn-off stars, which can be interpreted as the
signature of atomic diffusion. Qualitatively stellar models with
diffusion agree with the observed abundance results. Some turn-off
stars do not follow the general pattern, which suggests that in some
cases diffusion can be inhibited.
Our results thus pose a challenge for chemical tagging using the
turn-off stars since they are likely not chemically homogeneous.
Meanwhile, our results suggest that the effect of atomic diffusion
could be as large as 0.1-0.2dex, and must be taken into account when
using the current surface abundances of stars for chemical tagging.
Description:
Atomic line data, as well as the measured equivalent widths, adopted
for our analysis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 83 8 Information of our programme stars (+ HeBe)
tablea1.dat 94 206 Atomic line data, as well as the EW measurements,
adopted for our analysis
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Object Object name
(YNNNN, Cl* NGC 2682 YBP NNNN in Simbad)
7- 23 A17 --- 2MASS 2MASS ID (JHHMMSSss+DDMMSSs)
25- 29 F5.2 mag Bmag ? B magnitude
31- 35 F5.2 mag Vmag ? V magnitude
37- 43 F7.3 mas/yr pmRA ? Gaia DR2 (Cat I/345) proper motion along RA,
pmRA*cosDE
45- 50 F6.3 mas/yr pmDE ? Gaia DR2 (Cat I/345) proper motion along DE
52- 56 F5.3 mas/yr e_pmRA ? Gaia DR2 (Cat I/345) rms uncertainty on pmRA
58- 62 F5.3 mas/yr e_pmDE ? Gaia DR2 (Cat I/345) rms uncertainty on pmDE
64- 69 F6.4 mas Plx ? Gaia DR2 (Cat I/345) absolute parallax
71- 76 F6.4 mas e_Plx ? Gaia DR2 (Cat I/345) rms uncertainty on Plx
78- 80 I3 % Pmemb ? Probability of being a member of M67, taken
from Yadav et al. (2008, Cat. J/A+A/484/609)
82- 83 A2 --- Type ? Stellar type (1)
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Note (1): Stellar type as follows:
SG = sub-giant star
TO = turn-off star
ST = solar twin
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 0.1nm lambda Wavelength (Angstrom)
12- 15 A4 --- Species Species
19- 22 F4.2 eV Ep Lower excitation potential
26- 30 F5.2 [-] loggf Oscillator strength
34- 38 F5.1 10-4nm EW1 Equivalent widths for asteroid Hebe (mÅ)
42- 46 F5.1 10-4nm EW2 Equivalent widths for star Y1194 (mÅ)
50- 54 F5.1 10-4nm EW3 Equivalent widths for star Y1388 (mÅ)
58- 62 F5.1 10-4nm EW4 Equivalent widths for star Y1844 (mÅ)
66- 70 F5.1 10-4nm EW5 Equivalent widths for star Y2235 (mÅ)
74- 78 F5.1 10-4nm EW6 Equivalent widths for star Y519 (mÅ)
82- 86 F5.1 10-4nm EW7 Equivalent widths for star Y535 (mÅ)
90- 94 F5.1 10-4nm EW8 Equivalent widths for star Y923 (mÅ)
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Acknowledgements:
Fan Liu, fan.liu(at)astro.lu.se
(End) Patricia Vannier [CDS] 06-Jun-2019