J/A+A/619/A134 ATHOS. Flux ratio based stellar parameterization (Hanke+, 2018)
ATHOS: On-the-fly stellar parameter determination of FGK stars based on flux
ratios from optical spectra.
Hanke M., Hansen C. J., Koch A., Grebel E.K.
<Astron. Astrophys. 619, A134 (2018)>
=2018A&A...619A.134H 2018A&A...619A.134H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, fundamental ; Atomic physics ; Spectroscopy ;
Abundances, [Fe/H] ; Effective temperatures
Keywords: methods: data analysis - surveys - techniques: spectroscopic -
stars: abundances - stars: fundamental parameters
Abstract:
The rapidly increasing number of stellar spectra obtained by existing
and future large-scale spectroscopic surveys feeds a demand for fast
and efficient tools for the spectroscopic determination of fundamental
stellar parameters. Such tools should not only comprise customized
solutions for one particular survey or instrument, but, in order to
enable cross-survey comparability, they should also be capable of
dealing with spectra from a variety of spectrographs, resolutions, and
wavelength coverages. To meet these ambitious specifications, we
developed ATHOS (A Tool for HOmogenizing Stellar parameters), a
fundamentally new analysis tool that adopts easy-to-use,
computationally inexpensive analytical relations tying flux ratios
(FRs) of designated wavelength regions in optical spectra to the
stellar parameters effective temperature (Teff), iron abundance
([Fe/H]), and surface gravity (logg). Our Teff estimator is based on
FRs from nine pairs of wavelength ranges around the Balmer lines
Hβ and Hα, while for [Fe/H] and logg we provide 31 and 11
FRs, respectively, which are spread between ∼4800Å and ∼6500Å; a
region covered by most optical surveys. The analytical relations
employing these FRs were trained on N=124 real spectra of a stellar
benchmark sample that covers a large parameter space of Teff~=4000 to
6500K (spectral types F to K), [Fe/H]~=-4.5 to 0.3dex, and logg~=1 to
5dex, which at the same time reflects ATHOS' range of applicability.
We find accuracies of 97K for Teff, 0.16dex for [Fe/H], and 0.26dex
for logg, which are merely bounded by finite uncertainties in the
training sample parameters. ATHOS' internal precisions can be better
by up to 70%. We tested ATHOS on six independent large surveys
spanning a wide range of resolutions (R~=2000 to 52000), amongst
which are the Gaia-ESO and the SDSS/SEGUE surveys. The exceptionally
low execution time (<30ms per spectrum per CPU core) together with a
comparison to the literature parameters showed that ATHOS can
successfully achieve its main objectives, in other words fast stellar
parametrization with cross-survey validity, high accuracy, and high
precision. These are key to homogenize the output from future surveys,
such as 4MOST or WEAVE.
Description:
The stellar parameters and spectrographs for the spectra in the
training sample are presented together with their original parameter
source. Some stellar parameters were re-determined in an LTE abundance
approach. The involved atomic data for transitions of FeI and FeII
used in this work are given.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 28 223 Atomic data for FeI and FeII
table2.dat 62 195 Stellar parameters for the benchmark sample
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See also:
III/281 : Gaia FGK benchmark stars v2.1 (Jofre+, 2018)
J/ApJ/626/446 : Effective temperature scale of FGK stars (Ramirez+, 2005)
J/MNRAS/371/879 : Effective temperatures of 215 FGK giants (Kovtyukh+, 2006)
J/A+A/520/A79 : Nearby FGK stars chromospheric activity
(Martinez-Arnaiz+, 2010)
J/ApJ/735/41 : Carbon and oxygen abundances in FGK stars (Petigura+, 2011)
J/A+A/545/A32 : Chemical abundances of 1111 FGK stars (Adibekyan+, 2012)
J/A+A/547/A106 : Li abundances in the FGK dwarfs (Mishenina+, 2012)
J/A+A/552/A27 : Stellar activity and kinematics of FGK stars (Murgas+, 2013)
J/A+A/556/A86 : FGK dwarf stars limb darkening coefficients (Neilson+, 2013)
J/MNRAS/442/220 : Lick indices for FGK stars (Franchini+, 2014)
J/MNRAS/445/2223 : Mass estimation for FGK stars (Pinheiro+, 2014)
J/ApJ/764/78 : Oxygen abundances in nearby FGK stars (Ramirez+, 2013)
J/A+A/575/A89 : Center-to-limb polarization of FGK stars (Kostogryz+, 2015)
J/A+A/586/A87 : Center-to-limb polarization of FGK stars (Kostogryz+, 2016)
J/MNRAS/456/1221 : FGK dwarfs atmospheric parameters (Ryabchikova+, 2016)
J/A+A/606/A94 : Chemical abundances of 1059 FGK stars (Delgado Mena+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 0.1nm lambda Wavelength
10- 14 A5 --- Ion Ion designation (Fe I or Fe II)
16- 21 F6.3 eV chiex Excitation potential
23- 28 F6.3 [-] loggf Oscillator strength
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- ID Star identifier
19- 22 I4 K Teff Effective temperature
24- 26 I3 K e_Teff Uncertainty on Teff
28- 31 F4.2 [-] logg Surface gravity
33- 36 F4.2 [-] e_logg Uncertainty on logg
38- 42 F5.2 [-] [Fe/H] Metallicity
44- 47 F4.2 [-] e_[Fe/H] Uncertainty on [Fe/H]
49- 56 A8 --- spectr Spectrograph
58 I1 --- SrcFlag [1/4] Source flag (1)
60- 62 A3 --- ParFlag [1,2]? Re-determined parameters (2)
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Note (1): Original source for the stellar parameters:
1 = Jofre et al. (2014A&A...564A.133J 2014A&A...564A.133J),
Heiter et al. (2015A&A...582A..49H 2015A&A...582A..49H),
Hawkins et al. (2016A&A...592A..70H 2016A&A...592A..70H)
2 = Hansen et al. (2012A&A...545A..31H 2012A&A...545A..31H)
3 = Roederer et al. (2014AJ....147..136R 2014AJ....147..136R)
4 = For & Sneden (2010AJ....140.1694F 2010AJ....140.1694F), Afsar et al. (2012AJ....144...20A 2012AJ....144...20A)
Note (2): Parameters were re-determined in this work:
1 = Teff and [Fe/H] were newly deduced by enforcing excitation balance and
from FeII abundances, respectively
2 = logg was newly computed by demanding ionization balance between
abundances of FeI and FeII transitions
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Acknowledgements:
Michael Hanke, mhanke(at)ari.uni-heidelberg.de
(End) Michael Hanke [ARI, Germany], Patricia Vannier [CDS] 08-Sep-2018