J/MNRAS/505/5340 Lithium-rich stars in the GALAH survey DR3 (Martell+, 2021)
The GALAH survey a census of lithium-rich giant stars.
Martell S.L., Simpson J.D., Balasubramaniam A.G., Buder S., Sharma S.,
Hon M., Stello D., Ting Y.-S., Asplund M., Bland-Hawthorn J.,
De Silva G.M., Freeman K.C., Hayden M., Kos J., Lewis G.F., Lind K.,
Zucker D.B., Zwitter T., Campbell S.W., Cotar K., Horner J., Montet B.,
Wittenmyer R.
<Mon. Not. R. Astron. Soc., 505, 5340-5355 (2021)>
=2021MNRAS.505.5340M 2021MNRAS.505.5340M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Stars, giant ; Optical ;
Infrared sources ; Effective temperatures ; Spectroscopy ;
Radial velocities ; Abundances, [Fe/H]
Keywords: stars: abundances - stars: evolution
Abstract:
We investigate the properties of 1262 red giant stars with high
photospheric abundances of lithium observed by the GALAH and K2-HERMES
surveys, and discuss them in the context of proposed mechanisms for
lithium enrichment and redepletion in giant stars. We confirm that
Li-rich giants are rare, making up only 1.2 per cent of our giant star
sample. We use stellar parameters from the third public data release
from the GALAH survey and a Bayesian isochrone analysis to divide the
sample into first-ascent red giant branch (RGB) and red clump (RC)
stars, and confirm these classifications using asteroseismic data from
K2. We find that RC stars are 2.5 times as likely to be lithium-rich
as RGB stars, in agreement with other recent work. The probability for
a star to be lithium-rich is affected by a number of factors, though
the causality in those correlations is not entirely clear. We show for
the first time that primary and secondary RC stars have distinctly
different lithium enrichment patterns. The data set discussed here is
large and heterogeneous in terms of evolutionary phase, metallicity,
rotation rate, and mass. We expect that if the various mechanisms that
have been proposed for lithium enrichment in evolved stars are in fact
active, they should all contribute to this sample of lithium-rich
giants at some level.
Description:
We construct our data set in order to expand the parameter space of
the study of lithium-rich giants. Combining the GALAH and K2-HERMES
catalogues provides a large initial set of red giant stars (RGBs) and
red clump stars (RCs). Observation for the both surveys use the same
instrumental setup, the HERMES spectrograph (Sheinis et al.
2015JATIS...1c5002S 2015JATIS...1c5002S) with the 2dF fibre positioning system (Lewis et
al. 2002MNRAS.333..279L 2002MNRAS.333..279L) at the 3.9 m Anglo-Australian Telescope to
take high-resolution (R ∼ 28 000) spectra for stars in the Milky
Way. HERMES records ∼1000 Å across four non-contiguous sections of
the optical spectrum, including the region around the Hαline,
which contains the lithium resonance line at 6708 Å.
For this work, we are using the GALAH Data Release 3 catalogue (Buder
et al. 2021MNRAS.506..150B 2021MNRAS.506..150B, Cat. J/MNRAS/506/150) stellar parameters
and abundances. This contains 588 571 stars, all of which are found
in Gaia DR2 (Gaia Collaboration 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345) and
most of which are in the AllWISE catalogue (Mainzer et al.
2011ApJ...731...53M 2011ApJ...731...53M).
We apply a number of selections in data quality and stellar parameters
to identify a sample of reliable Li-rich giant stars such as no
problems noted in the input data, reduction, analysis and the iron
abundance determination. Additionally, we select a calculated
E(B-V) < 0.33 and a photometric measurement in the WISE W2 band with a data
quality flags as the WISE photometry is used as part of the
identification of RC stars. Moreover, we also excluded stars in the
Small Magellanic Cloud (SMC) or Large Magellanic Cloud (LMC). Finally,
we restrict ourselves to giant stars, selecting those stars found to
have effective temperature in the rang 3000 K < Teff < 5730 K and
surface gravity in the range 3.2 ≥ log g ≥ -1.0 which give us 109340
identified as giant stars, (see section 2.2 Giant star selection).
The lithium abundance of each star was determined as part of the main
analysis of the GALAH and K2 data sets from synthesis of the 6708 Å
lithium line. For our giant star sample, 1262 stars reveale a lithium
abundance value ALi up to 1.5 including 323 stars with ALi up to 2.7
considering as super-Li-rich stars, (see section 2.3 Lithium
abundances). The table1.dat lists stellar parameters, spectroscopic
information and RGB/RC classifications (see section 2.4 Classifying
evolutionary phase for more details) for this sample of 1262 Li-rich giants.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 238 1262 *Parameters and spectroscopic informations of
our 1262 Li-rich giants sample
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Note on table1.dat: Except Lithium abundance values ALi and SpType stellar
classification determined in this work, others parameters and spectroscopic
values come from the GALAH survey DR3 (Buder et al. 2021MNRAS.506..150B 2021MNRAS.506..150B,
Cat. J/MNRAS/506/150).
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See also:
II/328 : AllWISE Data Release (Cutri+ 2013)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/156 : LAMOST DR7 catalogs (Luo+, 2019)
J/ApJ/765/L41 : Asteroseismic classification of KIC objects
(Stello+, 2013)
J/ApJ/835/83 : K2 GAP data release. I. Campaign 1 (Stello+, 2017)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
J/ApJ/889/L34 : Oscillations in red giants from TESS data (Silva+, 2020)
J/MNRAS/465/3203 : GALAH observational overview (Martell+, 2017)
J/MNRAS/478/4513 : GALAH Survey DR2 (Buder+, 2018)
J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR2 Gaia DR2 source identifier
(Gaia DR2 source_id)
21- 41 F21.17 deg RAdeg Right Ascension (ICRS) at Ep=2015.5 (RA)
43- 63 F21.17 deg DEdeg Declination (ICRS) at Ep=2015.5 (Dec)
65- 78 F14.9 km/s RV Radial velocity (RV)
80- 98 F19.17 km/s e_RV Mean error of RV (e_RV)
100-108 F9.4 K Teff Effective temperature (Teff)
110-127 F18.14 K e_Teff Mean error of Teff (eTeff_)
129-138 F10.8 [cm/s2] logg Logarithm of stellar surface gravity (logg)
140-158 F19.17 [cm/s2] e_logg Mean error of logg (e_logg)
160-173 E14.11 [-] [Fe/H] Logarithm of the iron abundance ratio ([Fe/H])
175-194 F20.18 [-] e_[Fe/H] Mean error of [Fe/H] (e_[Fe/H])
196-213 F18.16 [-] ALi Logarithm of the lithium abundance (ALi) (1)
215-234 F20.18 [-] e_ALi Mean error of ALi (e_ALi)
236-238 A3 --- SpType [RC RGB] Red clump or Red giant branch
type (RCorRGB) (2)
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Note (1): We report the lithium abundance value in the form of
ALi = [Li/Fe] + [Fe/H] + 1.05, where the AX abundance scale gives
the number density of element X on a logarithmic scale relative
to hydrogen, with AH = 12 by definition, and 1.05 is the lithium
abundance of the Sun reported in Asplund et al. (2009ARA&A..47..481A 2009ARA&A..47..481A).
We follow the typical convention from the literature of considering
a giant star to be lithium-rich if its abundance ALi > 1.5,
(see section 2.3 Lithium abundances).
Note (2): The evolutionary state of lithium-rich giants is an essential piece
of knowledge for evaluating models to explain their enrichment.
The GALAH DR3 data set (Buder et al. 2021MNRAS.506..150B 2021MNRAS.506..150B,
Cat. J/MNRAS/506/150) contains two main populations of low-mass
giants in the Milky Way which are RGBs and RCs,
(see section 2.4 Classifying evolutionary phase).
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 14-Jun-2024