J/A+A/627/A173 Abundances for 4 metal-poor stars (Valentini+, 2019)
Masses and ages for metal-poor stars. A pilot program combining
asteroseismology and high-resolution spectroscopic follow-up of RAVE halo stars.
Valentini M., Chiappini C., Bossini D., Miglio A., Davies G.R., Mosser B.,
Elsworth Y.P., Mathur S., Garcia R.A., Girardi L., Rodrigues T.S.,
Steinmetz M., Vallenari A.
<Astron. Astrophys. 627, A173 (2019)>
=2019A&A...627A.173V 2019A&A...627A.173V (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Abundances ; Effective temperatures ;
Radial velocities
Keywords: stars: fundamental parameters - asteroseismology - stars: abundances
Abstract:
Very metal-poor halo stars are the best candidates for being among the
oldest objects in our Galaxy. Samples of halo stars with age
determination and detailed chemical composition measurements provide
key information for constraining the nature of the first stellar
generations and the nucleosynthesis in the metal-poor regime. Age
estimates are very uncertain and are available for only a small number
of metal-poor stars. Here we present the first results of a pilot
program aimed at deriving precise masses, ages and chemical abundances
for metal-poor halo giants using asteroseismology, and high-resolution
spectroscopy. We obtained high-resolution UVES spectra for four
metal-poor RAVE stars observed by the K2 satellite. Seismic data
obtained from K2 light curves helped improving spectroscopic
temperatures, metallicities and individual chemical abundances. Mass
and ages were derived using the code PARAM, investigating the effects
of different assumptions (e.g. mass loss, [alpha/Fe]-enhancement).
Orbits were computed using Gaia DR2 data. {The stars are found to be
"normal" metal-poor halo stars (i.e. non C-enhanced), with an
abundance pattern typical of old stars (i.e. alpha and Eu-enhanced),
and with masses in the 0.80-1.0M☉ range. The inferred
model-dependent stellar ages are found to range from 7.4 to 13.0Gyr,
with uncertainties of ∼30%-35%. We also provide revised masses and
ages for metal-poor stars with Kepler seismic data from APOGEE survey
and a set of M4 stars. The present work shows that the combination of
asteroseismology and high-resolution spectroscopy provides precise
ages in the metal-poor regime. Most of the stars analysed in the
present work (covering the metallicity range of [Fe/H]~-0.8 to -2dex),
are very old >9Gyr (14 out of 19 stars), and all of them are older
than >5Gyr (within the 68 percentile confidence level).
Description:
Linelist used for deriving atmospheric parameters and abundances.
Atmospheric parameters and element abundances of the stars (EPIC ID)
201359581, 205997746 , 206034668, and 206443679 are provided.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 143 4 Atmospheric parameters of the 4 stars
tableb1.dat 69 20 Chemical abundances derived for the metal-poor
stars presented in this work
linelist.dat 47 300 Linelist adopted in the work
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Name [S1 S2 S3 S4] Star name
4- 12 I9 --- EPIC EPIC_ID
14- 23 F10.6 deg RAdeg Right ascension (J2000) (1)
25- 33 F9.5 deg DEdeg Declination (J2000) (1)
35- 38 I4 K TeffG GAIA DR2 effective temperature
40- 42 I3 K e_TeffG rms uncertainty on GAIA DR2
effective temperature
44- 50 F7.2 km/s RVG GAIA DR2 radial velocity
52- 55 F4.2 km/s e_RVG rms uncertainty on GAIA DR2 radial velocity
57- 60 F4.2 [cm/s2] loggG GAIA DR2 surface gravity derived
with parallax
62- 65 F4.2 [cm/s2] e_loggG rms uncertainty on GAIA DR2 surface gravity
derived with parallax
67- 70 I4 K Teff Classical effective temperature
72- 73 I2 K e_Teff rms uncertainty on classical
effective temperature
75- 78 F4.2 [cm/s2] logg Classical surface gravity
80- 83 F4.2 [cm/s2] e_logg rms uncertainty on classical surface gravity
85- 88 I4 K TeffS Effective temperature with Seismo
90- 91 I2 K e_TeffS rms uncertainty on effective temperature
with Seismo
93- 96 F4.2 [cm/s2] loggS Surface gravity with Seismo
98-101 F4.2 [cm/s2] e_loggS rms uncertainty on surface gravity
with Seismo
103-106 F4.2 km/s vmicS Micro-turbulence velocity with Seismo
108-110 F3.1 km/s e_vmicS rms uncertainty on micro-turbulence
velocity with Seismo
112-118 F7.2 km/s RVS Radial velocity with Seismo
120-123 F4.2 km/s e_RVS rms uncertainty on radial velocity
with Seismo
125-143 I19 --- GaiaDR2 Gaia DR2 source number (source_id)
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Note (1): Positions from table2 of the paper.
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Species Chemical element for which abundances are
provided
7- 10 F4.1 -- Z Atomic number of the chemical element
12- 13 I2 --- o_AbdS1 ?=- Number of lines used for the
element abundance for star S1
15- 19 F5.2 --- AbdS1 ?=- Element abundance for star S1
21- 24 F4.2 --- e_AbdS1 ?=- Error on element abundance for star S1
26- 27 I2 --- o_AbdS2 ?=- Number of lines used for the
element abundance for star S2
29- 33 F5.2 --- AbdS2 Element abundance for star S2
35- 38 F4.2 --- e_AbdS2 Error on element abundance for star S2
40- 41 I2 --- o_AbdS3 ?=- Number of lines used for the
element abundance for star S3
43- 47 F5.2 --- AbdS3 Element abundance for star S3
49- 52 F4.2 --- e_AbdS3 Error on element abundance for star S3
54- 55 I2 --- o_AbdS4 ?=- Number of lines used for the
element abundance for star S4
57- 61 F5.2 --- AbdS4 ?=- Element abundance for star S4
63- 66 F4.2 --- e_AbdS4 ?=- Error on element abundance for star S4
68- 69 A2 --- Method Method used for abundance measurement (1)
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Note (1): Methods as follows:
ew = equivalent width
f = fit
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Byte-by-byte Description of file: linelist.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 11 F9.4 0.1nm lambda Line wavelength in Angstroem
15- 23 F9.5 --- ID Atom or molecule identification number
29- 34 F6.4 eV EP Line excitation potential
42- 47 F6.3 [-] log(gf) Line log(gf)
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Acknowledgements:
Marica Valentini, mvalentini(at)aip.de
(End) Marica Valentini [AIP, Germany], Patricia Vannier [CDS] 09-Jul-2019