J/MNRAS/489/4641 APOKASC Evolutionary state of red-giant stars (Elsworth+, 2019)
Insights from the APOKASC determination of the evolutionary state of red-giant
stars by consolidation of different methods.
Elsworth Y., Hekker S., Johnson J.A., Kallinger T., Mosser B.,
Pinsonneault M., Hon M., Kuszlewicz J., Miglio A., Serenelli A., Stello D.,
Tayar J., Vrard M.
<Mon. Not. R. Astron. Soc., 489, 4641-4657 (2019)>
=2019MNRAS.489.4641E 2019MNRAS.489.4641E (SIMBAD/NED BibCode)
ADC_Keywords: Asteroseismology ; Stars, giant ; Stars, late-type ;
Spectroscopy ; Optical ; Infrared
Keywords: asteroseismology - stars: evolution - stars: low-mass -
stars: oscillations
Abstract:
The internal working of low-mass stars is of great significance to
both the study of stellar structure and the history of the Milky Way.
Asteroseismology has the power to directly sense the internal
structure of stars and allows for the determination of the
evolutionary state - i.e. has helium burning commenced or is the
energy generated only by the fusion in the hydrogen-burning shell? We
use observational data from red-giant stars in a combination (known as
APOKASC) of asteroseismology (from the Kepler mission) and
spectroscopy (from SDSS/APOGEE). The new feature of the analysis is
that the APOKASC evolutionary state determination is based on the
comparison of diverse approaches to the investigation of the
frequency-power spectrum. The high level of agreement between the
methods is a strong validation of the approaches. Stars for which
there is not a consensus view are readily identified. The comparison
also facilitates the identification of unusual stars including those
that show evidence for very strong coupling between p and g cavities.
The comparison between the classification based on the spectroscopic
data and asteroseismic data have led to a new value for the
statistical uncertainty in APOGEE temperatures. These consensus
evolutionary states will be used as an input for methods that derive
masses and ages for these stars based on comparison of observables
with stellar evolutionary models ('grid-based modelling') and as a
training set for machine-learning and other data-driven methods of
evolutionary state determination.
Description:
We obtained frequency power spectra from the time-series observed
during the Kepler mission (Borucki et al. 2010Sci...327..977B 2010Sci...327..977B) and
near-infrared spectra from the APOGEE Survey (Eisenstein et al.
2011AJ....142...72E 2011AJ....142...72E; Majewski et al. 2017AJ....154...94M 2017AJ....154...94M, Cat.
III/284) for thousands of red giants. We refer to this combination as
APOKASC.
We used four individual seismic methods and a spectroscopic method for
determining the evolutionary states of individual stars. The
characteristics of the methods are quite different which is a strength
of the use of the four together to obtain consensus determination of
the evolutionary state of individual stars. All the methods aim to
separate first ascent RGB stars from RC stars. However, with the
exception of Method 3, the methods are unable to distinguish between
RGB and asymptotic giant branch (AGB) stars. There are particular
difficulties to seismically identify AGB stars and to distinguish them
from high-luminosity RGB stars.
The evolutionary state determinations of the four different seismic
methods are used together to produce a consensus value of the
evolutionary state for every individual star. In some cases the
consensus value is entirely obvious because all the methods agree.
However, lower levels of agreement can still be useful but it is
important for later application of these results that there is a
record of the level of agreement in the input values used. This record
is provided in table A1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 43 6661 Table of evolutionary states giving the
consensus state and the individual ones for
a sample of stars
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
J/AJ/151/68 : Kepler Mission. VII. Eclipsing binaries in DR3 (Kirk+, 2016)
J/MNRAS/466/3344 : Red-giant stars classification (Elsworth+, 2017)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- KIC KIC identifier (NNNNNNNN)
10- 16 A7 --- cons Consensus evolutionary stage (1)
18- 22 A5 --- evol1 Evolutionary stage from method 1
(Elsworth et al. 2017MNRAS.466.3344E 2017MNRAS.466.3344E,
Cat. J/MNRAS/466/3344) (2)
24- 26 A3 --- evol2 Evolutionary stage from method 2
(Hekker et al. 2017EPJWC.16004006H 2017EPJWC.16004006H) (3)
28- 30 A3 --- evol3 Evolutionary stage from method 3
(Kallinger et al. 2012A&A...541A..51K 2012A&A...541A..51K) (4)
32- 34 A3 --- evol4 Evolutionary stage from method 4
(Mosser et al. 2015A&A...584A..50M 2015A&A...584A..50M) (5)
36- 43 A8 --- spec Evolutionary stage from the spectroscopic
method (6)
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Note (1): Consensus evolutionary stage as follows:
2CL = Secondary clump star (286/6661)
2CL/U = Uncertain secondary clump star (20/6661)
AGB/U = Uncertain asymptotic giant branch star (1/6661)
RC = Red clump star (1984/6661)
RC/2CL = Red clump or secondary clump star (179/6661)
RC/U = Uncertain red clump star (88/6661)
RGB = Red giant branch star (3372/6661)
RGB/AGB = Red giant branch or asymptotic giant branch star (260/6661)
RGB/U = Uncertain red giant branch star (7/6661)
U = Uncertain classification (4/6661)
See section 5 of the article for more details
Note (2): Method 1 (Elsworth et al. 2017MNRAS.466.3344E 2017MNRAS.466.3344E, Cat. J/MNRAS/466/3344)
is an autonomous way of determining the evolutionary state from an
analysis of the morphology of the power spectrum of the light curve.
(See section 3.1 of the article for more details)
Note (3): Method 2 (Hekker et al. 2017EPJWC.16004006H 2017EPJWC.16004006H) is based on grid-based
modelling using the global asteroseismic parameters νmax and
Δν, combined with effective temperature and metallicity.
(See section 3.2 of the article for more details)
Note (4): Method 3 (Kallinger et al. 2012A&A...541A..51K 2012A&A...541A..51K) uses established
methods automatically to locate and measure the frequencies of the
radial modes. (See section 3.3 of the article for more details)
Note (5): Method 4 is based on the measurement of the asymptotic period
spacings, as given by Vrard, Mosser & Samadi (2016A&A...588A..87V 2016A&A...588A..87V),
which relies on the asymptotic fit of the mixed-mode pattern.
(See section 3.4 of the article for more details)
Note (6): Spectroscopic classification of evolutionary states based on
temperature, surface gravity, and metallicity. (See section 4 of the
article for more details)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 17-Jan-2023