J/ApJ/746/16 Modelling the convection zone (van Saders+, 2012)
The sensitivity of convection zone depth to stellar abundances: an absolute
stellar abundance scale from asteroseismology.
van Saders J.L., Pinsonneault M.H.
<Astrophys. J., 746, 16 (2012)>
=2012ApJ...746...16V 2012ApJ...746...16V
ADC_Keywords: Models ; Abundances ; Stars, ages ; Stars, masses ;
Effective temperatures
Keywords: stars: abundances - stars: interiors - stars: oscillations
Abstract:
The base of the convection zone (CZ) is a source of acoustic glitches
in the asteroseismic frequency spectra of solar-like oscillators,
allowing one to precisely measure the acoustic depth to the feature.
We examine the sensitivity of the depth of the CZ to mass, stellar
abundances, and input physics, and in particular, the use of a
measurement of the acoustic depth to the CZ as an
atmosphere-independent, absolute measure of stellar metallicities. We
find that for low-mass stars on the main sequence with
0.4M☉≤M≤1.6M☉, the acoustic depth to the base of the CZ,
normalized by the acoustic depth to the center of the star,
τcz,n, is both a strong function of mass, and varies at the
0.5%-1% per 0.1 dex level in [Z/X], and is therefore also a sensitive
probe of the composition. We estimate the theoretical uncertainties in
the stellar models and show that combined with reasonable
observational uncertainties we can expect to measure the metallicity
to within 0.15-0.3 dex for solar-like stars. We discuss the
applications of this work to rotational mixing, particularly in the
context of the observed mid-F star Li dip, and to distinguishing
between different mixtures of heavy elements.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 106 4613 Model grid of the convection zone
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See also:
J/A+AS/128/29 : X-ray/opt. obs. of stars with shallow CZ (Piters+ 1998)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 F5.3 Msun Mass [0.4/1.6] Model mass
7- 11 F5.3 --- Yi [0.24/0.28] Initial helium abundance
13- 17 F5.2 [Sun] [Z/X]i [-1.2/0.6] Initial model [Z/X] (1)
19- 27 E9.3 [Sun] [Z/X] [-4.28/0.601] Surface [Z/X] at given age
29- 34 F6.3 Gyr Age [0.5/10] Model age (0.5, 1, 5 or 10)
36- 46 F11.8 [Lsun] logL [-1.728/0.749] Log luminosity
48- 58 F11.8 [Rsun] logR [-0.45/0.25] Log radius
60- 63 I4 K Teff [3572/7257] Effective temperature
65- 74 F10.7 [Sun] logrho [-0.566/0.947] Sun-relative log mean density (2)
76- 82 F7.5 --- Rcz/R [0/1] Fractional radius of convection zone
84- 91 F8.3 s taucz [0/4107] Acoustic depth of convection zone (3)
93- 98 F6.1 s tau* [0/8217] Acoustic crossing time (3)
100-106 F7.5 --- taucz.n [0.016/0.992] Normalized acoustic depth (3)
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Note (1): Referenced to the initial Z/X of a calibrated solar model.
Note (2): Given by log(M*R-3/(M☉*R☉-3)).
Note (3): Definitions are (R is the star radius):
* the acoustic depth τ is defined as dτ=dr/cs, where r is
the radius and cs the sound speed;
* the acoustic depth τcz is the acoustic depth of the convection zone,
i.e. τcz=∫dτ over the range r=Rcz to r=R;
* the acoustic crossing time τ* is the acoustic depth of the center,
i.e. τ*=∫dτ over the range r=0 to r=R;
* the normalized acoustic depth is relative to the acoustic crossing time,
i.e. τcz,n=τcz/τ*
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Aug-2013