J/A+A/675/A23 IGRINS. M giant abundances (Nandakumar+, 2023)
M giants with IGRINS. I. Stellar parameters and alpha-abundance trends of the
solar neighborhood population.
Nandakumar G., Ryde N., Casagrande L., Mace G.
<Astron. Astrophys. 675, A23 (2023)>
=2023A&A...675A..23N 2023A&A...675A..23N (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, giant ; Stars, K-type ; Abundances ;
Spectra, infrared
Keywords: stars: fundamental parameters - stars: abundances - stars: late-type -
techniques: spectroscopic - Galaxy: abundance
Abstract:
Cool stars, such as M giants, can only be analyzed in the
near-infrared (NIR) regime due to the ubiquitous titanium oxide
features in optical spectra of stars with Teff<4000K. In dust-obscured
regions, the inner bulge and Galactic center region, the intrinsically
bright M giants observed in the NIR are an optimal option for studying
stellar abundances and the chemical evolution of stellar populations.
Because of the uncertainties in photometric methods, a method for
determining the stellar parameters for M giants from the NIR spectra
themselves is needed.
We develop a method for determining the stellar parameters for M
giants from the NIR spectra. We validate the method by deriving the
stellar parameters for nearby well-studied M giants with spectra from
the spectral library of the Immersion GRating INfrared Spectrograph
(IGRINS). We demonstrate the accuracy and precision of our method by
determining the stellar parameters and alpha-element trends versus
metallicity for solar neighborhood M giants.
We carried out new observations of 44 M giant stars with IGRINS
mounted on the Gemini South telescope. We also obtained the full H and
K band IGRINS spectra of six nearby well-studied M giants at a
spectral resolving power of R=45000 from the IGRINS spectral library.
We used the tool called spectroscopy made easy in combination with
one-dimensional (1D) model atmospheres in a radiative and convective
scheme (MARCS) stellar atmosphere models to model the synthetic
spectrum that fits the observed spectrum best.
The effective temperatures that we derive from our new method (tested
for 3400≤Teff≤4000K here) agree excellently with those of the
six nearby well-studied M giants, which indicates that the accuracy is
indeed high. For the 43 solar neighborhood M giants, our Teff, logg,
[Fe/H], microturbulence, [C/Fe], [N/Fe], and [O/Fe] agree with APOGEE
with mean differences and a scatter (our method - APOGEE) of
-67±33K, -0.31±0.15dex, 0.02±0.05dex, 0.22±0.13km/s,
-0.05±0.06dex, 0.06±0.06dex, and 0.02±0.09dex, respectively.
Furthermore, the tight offset with a small dispersion compared to the
APOGEE Teff indicates a high precision in our derived temperatures
and those derived from the APOGEE pipeline. The typical uncertainties
in the stellar parameters are found to be ±100K in Teff, ±0.2dex
in logg, ±0.1dex in [Fe/H], and ±0.1km/s in microturbulence. The
alpha-element trends versus metallicity for Mg, Si, Ca, and Ti are
consistent with the APOGEE DR17 trends for the same stars and with the
GILD optical trends. We also find a clear enhancement in the
abundances for thick-disk stars.
Description:
We present stellar parameters and alpha abundances measured from the
infrared HK band for 50 M giants in the solar neighbourhood. The
spectra were obtained with the spectrograph IGRINS Gemini South
telescope. The spectra have R=45000. The S/N of the spectra is
generally high, with the majority of them having values above 100.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 76 44 Stellar parameters and phosphorus abundances
for sample stars, along with their assumed
stellar population and [O/Fe] based on the
APOGEE [Mg/Fe] vs. [Fe/H] trend
tablea6.dat 47 46 Line-by-line Magnesium abundances and mean
[Mg/Fe]
tablea7.dat 53 46 Line-by-line Silicon abundances and mean [Si/Fe]
tablea8.dat 59 46 Line-by-line Calcium abundances and mean [Ca/Fe]
tablea9.dat 41 46 Line-by-line Titanium abundances and mean
[Ti/Fe]
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Star Name (2M)
20- 24 A5 --- Pop Designated stellar population
26- 29 I4 K Teff Effective temperature
31- 34 F4.2 [cm/s2] logg Surface gravity
36- 40 F5.2 [-] [Fe/H] Relative iron abundance
42- 45 F4.2 km/s vmicro Microturbulence velocity
47- 51 F5.2 [-] [C/Fe] Relative Carbon abundance
53- 56 F4.2 [-] [N/Fe] Relative Nitrogen abundance
58- 62 F5.2 [-] [O/Fe] Relative Oxygen abundance
64- 74 A11 --- CM Stars observed by other surveys based on
cross match (RAVE and/or GALAH)
76 A1 --- n_CM [a] Note (1)
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Note (1): Note as follows:
a = No IRFM Teff in GALAH DR3
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Byte-by-byte Description of file: tablea6.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Star Name (2M,HD,HIP)
20- 24 F5.2 [-] AMg21059.76 Mg abundance from 21059.76Å line
26- 30 F5.2 [-] AMg21060.89 Mg abundance from 21060.89Å line
32- 36 F5.2 [-] AMg21458.87 Mg abundance from 21458.87Å line
38- 42 F5.2 [-] [Mg/Fe] Mean Mg abundance
44- 47 F4.2 [-] e_[Mg/Fe] Standard mean of error
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Byte-by-byte Description of file: tablea7.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Star Name (2M,HD,HIP)
20- 24 F5.2 [-] ASi16434.93 Si abundance from 16434.93Å line
26- 30 F5.2 [-] ASi20804.20 ?=-9.99 Si abundance from 20804.20Å line
32- 36 F5.2 [-] ASi20890.37 ?=-9.99 Si abundance from 20890.37Å line
38- 42 F5.2 [-] ASi20926.14 ?=-9.99 Si abundance from 20926.14Å line
44- 48 F5.2 [-] [Si/Fe] Mean Si abundance
50- 53 F4.2 [-] e_[Si/Fe] Standard mean of error
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Byte-by-byte Description of file: tablea8.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Star Name (2M,HD,HIP)
20- 24 F5.2 [-] ACa16150.76 Ca abundance from 16150.76Å line
26- 30 F5.2 [-] ACa16155.24 Ca abundance from 16155.24Å line
32- 36 F5.2 [-] ACa16157.36 Ca abundance from 16157.36Å line
38- 42 F5.2 [-] ACa20962.57 Ca abundance from 20962.57Å line
44- 48 F5.2 [-] ACa20972.53 Ca abundance from 20972.53Å line
50- 54 F5.2 [-] [Ca/Fe] Mean Ca abundance
56- 59 F4.2 [-] e_[Ca/Fe] Standard mean of error
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Byte-by-byte Description of file: tablea9.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Star Name (2M,HD,HIP)
20- 24 F5.2 [-] ATi16330.54 Ti abundance from 16330.54Å line
26- 30 F5.2 [-] ATi21149.62 ?=-9.99 Ti abundance from 21149.62Å line
32- 36 F5.2 [-] [Ti/Fe] Mean Ti abundance
38- 41 F4.2 [-] e_[Ti/Fe] Standard mean of error
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Acknowledgements:
Govind Nandakumar, govind.iist(at)gmail.com
(End) Patricia Vannier [CDS] 30-May-2023