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VI/54 Horizontal Branch Stellar Model Calculations (Dorman 1992)
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Horizontal Branch Stellar Model Calculations
Dorman B.
<Astrophys. J. Suppl. Ser., 81, 221 (1992)>
=1992ApJS...81..221D
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ADC_Keywords: Abundances, [Fe/H] ; Isochrones ; Stars, horizontal branch
Description:
This data set consists of evolutionary sequences from the Zero Age
Horizontal Branch (ZAHB) to the point where log L/Lsun reaches 2.25 on
the lower AGB. These calculations have enhanced oxygen abundance
according to a relation used by VandenBerg (1992ApJ...391..685V) and
Bergbusch and VandenBerg (1992ApJS...81..163B) for main sequence
and red-giant branch models. Also, zero age sequences for oxygen
enhanced and scaled-solar compositions are given.
Introduction:
There are thirteen data files in this directory, ten of which contain
evolutionary sequences from the ZAHB to the point where log(L/Lsun)
reaches 2.25 on the lower AGB. These calculations have enhanced oxygen
abundance according to a relation used by VandenBerg (1992) and
Bergbusch and VandenBerg (1992) in computations of evolutionary tracks
and isochrones for main sequence and red-giant branch models. The
other three contain zero age sequences for oxygen enhanced and
scaled-solar compositions, as explained below. The models with
[O/Fe]>0 are described in more detail in Dorman (1992). Briefly, the
models use Los Alamos (1977) high temperature opacities, Alexander
(1980) low temperature opacities, the reaction rates listed in
Caughlan and Fowler (1988), and the Eggleton et. al. (1973) equation
of state. model atmospheres for surface pressures used by VandenBerg
(1992), and a mixing length of 1.5 pressure scale heights.
Accompanying scaled-solar evolution calculations may be available on
request, through the address given below. A complete bibliography for
the input physics in these models can be found from the 3 papers
listed in the References below.
Evolutionary sequences:
The ten files are for ten different compositions, lying between
[Fe/H]=-2.26 and -0.47. The filenames (f24a14.dat,f24b24.dat etc.) are
significant in the sense that the `24' which appears in every name
refers to the ZAMS helium abundance, to two significant figures. The
`14', `24', `34' etc. gives the mantissa and exponent of the value of
Z', the heavy element abundance of a model with the same [Fe/H], but
without the oxygen enhancement. Thus, f24j63.dat contains sequences
with the same iron abundance as scaled solar models with Z = 0.006. A
summary of the contents of each file is given below. The tables here
have been derived from the original calculations using cubic Hermite
spline interpolation, and are tabulated at even intervals of the
central helium abundances; the intervals change towards exhaustion.
After Y is exhausted at the centre of the model, the tracks are
tabulated at intervals of 0.25 Myr.
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Filename YHB [Fe/H] [O/Fe] Msh
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f24a14.dat 0.246 -2.26 0.75 0.4926
f24b24.dat 0.247 -2.03 0.70 0.4904
f24c34.dat 0.248 -1.78 0.66 0.4881
f24d44.dat 0.248 -1.66 0.63 0.4866
f24e64.dat 0.249 -1.48 0.60 0.4852
f24f13.dat 0.250 -1.26 0.55 0.4835
f24g23.dat 0.252 -1.03 0.50 0.4815
f24h33.dat 0.257 -0.78 0.39 0.4792
f24i43.dat 0.259 -0.65 0.30 0.4776
f24j63.dat 0.266 -0.47 0.23 0.4757
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Zero Age Horizontal Branch models:
There is one file for [O/Fe] > 0 models (zahbo.dat), and there are two
for scaled solar calculations. The first of these (zahb.dat) contains
ZAHB models for the [Fe/H] values which correspond to the enhanced
oxygen sets. The other (zahbs.dat), containing models for just 3
compositions, has data for [Fe/H] = -0.23, 0 and +0.15 ( Z = 0.01,
0.0169 and 0.024). These have been calculated with the Krishna-Swamy
scaled-solar T-tau relation and with mixing length 1.58 pressure
scaleheights. They are not consistent with the others, therefore, and
using them together to derive theoretical quantities as a function of
metallicity may give spurious results. All of the oxygen-enhanced
ZAHBs contain models for masses between about 0.5 and 1.5 solar
masses, while the range of the scaled-solar models varies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
f24a14.dat 114 595 Evolutionary sequence [Fe/H]=-2.26
f24b24.dat 114 615 Evolutionary sequence [Fe/H]=-2.03
f24c34.dat 114 665 Evolutionary sequence [Fe/H]=-1.78
f24d44.dat 114 586 Evolutionary sequence [Fe/H]=-1.66
f24e64.dat 114 496 Evolutionary sequence [Fe/H]=-1.48
f24f13.dat 114 498 Evolutionary sequence [Fe/H]=-1.26
f24g23.dat 114 564 Evolutionary sequence [Fe/H]=-1.03
f24h33.dat 114 497 Evolutionary sequence [Fe/H]=-0.78
f24i43.dat 114 472 Evolutionary sequence [Fe/H]=-0.65
f24j63.dat 114 424 Evolutionary sequence [Fe/H]=-0.47
zahb.dat 84 167 Zero Age Horizontal Branch model.
Scaled solar sequences
zahbo.dat 84 221 Zero Age Horizontal Branch model.
Enhanced O ZAHB Sequences
zahbs.dat 84 40 Zero Age Horizontal Branch model.
Scaled solar metal rich compositions
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Byte-by-byte Description of file: f*.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 solMass Mass Stellar mass
6- 10 F5.2 Sun [Fe/H] Metallicity relative to Sun (log scale)
11- 15 F5.2 Sun [O/Fe] Oxygen abundance relative to Sun (log scale)
17- 22 F6.2 Myr Age ? Age in Myr since ZAHB
24- 30 F7.4 --- Yc [0/1]? Central helium fraction
32- 37 F6.3 solLum logL ? Surface luminosity (log scale)
39- 44 F6.3 K logTe ? Effective temperature (log scale)
46- 51 F6.3 cm/s2 log.g ? Surface gravity, cgs units (log scale)
53- 58 F6.3 mag Mv Absolute Visual magnitude, derived from scale
described by VandenBerg (1992ApJ...391..685V)
60- 65 F6.3 mag B-V colour index
67- 72 F6.3 K logTc Central Temperature (log scale)
74- 79 F6.3 g/cm3 log.rho_c Central density, cgs units (log scale)
81- 86 F6.3 solMass Mccore ? Mass of convective core
88- 93 F6.3 solMass Mout ? Mass at outer edge of semiconvection zone
95-100 F6.3 solMass Msh Mass at peak energy production rate of
Hydrogen burning shell
102-107 F6.3 --- A ? A = log.L/M^0.81, a quantity arising from
pulsation models (1)
109-114 F6.3 d logP ? Period of RR Lyrae pulsation (log scale)
in the fundamental mode (1)
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Note (1): the two quantities A and logP are given for
3.79 < log T < 3.90.
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Byte-by-byte Description of file: zahb*.dat
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Bytes Format Units Label Explanations
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1- 5 F5.3 --- YHB [0/1] Helium abundance
6- 10 F5.2 Sun [Fe/H] Metallicity relative to Sun (log scale)
11- 15 F5.2 Sun [O/Fe] Oxygen abundance relative to Sun (log scale)
17- 21 F5.3 solMass Msh Core mass at He flash
23- 28 F6.2 solMass Mass Stellar mass (solar units)
30- 35 F6.3 solLum logL Surface luminosity (log scale)
37- 42 F6.3 K logTe Effective temperature (log scale)
44- 49 F6.3 cm/s2 log.g Surface gravity, cgs units (log scale)
51- 56 F6.3 mag Mv Absolute Visual magnitude
58- 63 F6.3 mag B-V colour index
65- 70 F6.3 cm logR Radius (log scale)
72- 77 F6.3 K logTc Central Temperature (log scale)
79- 84 F6.3 g/cm3 log.rho_c Central density, cgs units (log scale)
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Acknowledgements:
We thank Ben Dorman <bd4r@borealis.astro.Virginia.EDU>
for providing the files and the necessary explanations in early 1992.
References:
I. VandenBerg, D.A. 1992, ApJ, 391, 685 (1992ApJ...391..685V)
II. Bergbusch, P.A., VandenBerg, D.A. 1992, ApJS, 81, 163
(1992ApJS...81..163B)
III. Dorman, B. 1992 Ap. J. Supp. 81, July 1992 (1992ApJS...81..221D)
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(End) CDS Catalogue Service 04-Mar-1996