J/A+A/575/A12 Stellar CharactEristics Pisa Estimation gRid (Valle+, 2015)
Uncertainties in asteroseismic grid-based estimates of stellar ages.
SCEPtER: Stellar CharactEristics Pisa Estimation gRid.
Valle G., Dell'Omodarme M., Prada Moroni P.G., Degl'Innocenti S.
<Astron. Astrophys., 575, A12-12 (2015)>
=2015A&A...575A..12V 2015A&A...575A..12V
ADC_Keywords: Stars, masses ; Stars, ages ; Models
Keywords: methods: statistical - stars: evolution - stars: oscillations -
stars: low-mass - stars: fundamental parameters - asteroseismology
Abstract:
Stellar age determination by means of grid-based techniques that adopt
asteroseismic constraints is a well established method nowadays.
However some theoretical aspects of the systematic and statistical
errors affecting these age estimates still have to be investigated. We
study the impact on stellar age determination of the uncertainty in
the radiative opacity, in the initial helium abundance, in the
mixing-length value, in the convective core overshooting, and in the
microscopic diffusion efficiency adopted in stellar model
computations. We extended our SCEPtER grid to include stars with mass
in the range [0.8; 1.6]M☉ and evolutionary stages from the
zero-age main sequence to the central hydrogen depletion. For the age
estimation we adopted the same maximum likelihood technique as
described in our previous work. To quantify the systematic errors
arising from the current uncertainty in model computations, many
synthetic grids of stellar models with perturbed input were adopted.
We found that the current typical uncertainty in the observations
accounts for 1σ statistical relative error in age determination,
which on average ranges from about -35% to +42%, depending on the
mass. However, owing to the strong dependence on the evolutionary
phase, the age's relative error can be higher than 120% for stars near
the zero-age main sequence, while it is typically of the order of 20%
or lower in the advanced main-sequence phase. The systematic bias on
age determination due to a variation of ±1 in the helium-to-metal
enrichment ratio ΔY/ΔZ is about one-fourth of the
statistical error in the first 30% of the evolution, while it is
negligible for more evolved stages. The maximum bias due to the
presence of the convective core overshooting is -7% and -13% for mild
and strong overshooting scenarios. For all the examined models, the
impact of a variation of ±5% in the radiative opacity was found to
be negligible. The most important source of bias is the uncertainty in
the mixing-length value αml and the neglect of microscopic
diffusion. Each of these effects accounts for a bias that is nearly
equal to the random error uncertainty. Comparison of the results of
our technique with other grid techniques on a set of common stars
showed general agreement. However, the adoption of a different grid
can account for a variation in the mean estimated age up to 1Gyr.
Description:
We performed a theoretical investigation aimed to quantify the effect
of the current uncertainties in stellar models on the estimates of
star ages obtained by means of grid-based techniques, adopting
asteroseismic constraints. We analysed the uncertainties arising from
several inputs of stellar model computations: input physics, chemical
composition, and the efficiency of microscopic processes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 40 20 SCEPtER unweighted age and mass estimates for the
observational sample from Mathur et al. 2012
(J/ApJ/749/152)
table5.dat 40 73 SCEPtER age and mass estimates for the observational
sample from Chaplin et al. 2014 (J/ApJS/210/1)
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/ApJ/749/152 : Asteroseismic analysis of 22 solar-type stars (Mathur+, 2012)
J/ApJS/210/1 : Asteroseismic study of solar-type stars (Chaplin+, 2014)
Byte-by-byte Description of file: table3.dat table5.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [K]
2- 9 I8 --- KIC Star KIC number (V/133)
11- 15 F5.2 Gyr Age [0.9/14.5] Age
17- 20 F4.2 Gyr E_Age [0/2.6] Error in Age (upper value)
22- 25 F4.2 Gyr e_Age [0/2.6] Error in Age (lower value)
27- 30 F4.2 Msun Mass [0.8/1.6] Mass
32- 35 F4.2 Msun E_Mass [0/0.2] Error in Mass (upper value)
37- 40 F4.2 Msun e_Mass [0/0.2] Error in Mass (lower value)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 22-Jun-2015