White Dwarf Models
We will use the WD evolution code written by Martin Schwarzschild.
Subsequent modifications made by:
WDEC 1.0 Kutter & Savedoff (1969, ApJ, 157, 1021)
WDEC 2.0 D.Q. Lamb (1975, ApJ, 200, 306)
WDEC 3.0 D.E. Winget
WDEC 4.0 S.D. Kawaler
WDEC 5.0 M.A. Wood (aka WDXD)
WDEC 6.0 P.A. Bradley (aka WDXDL, WDEC6)
This particular version evolves c/o white dwarfs, using the old
radiative opacities, and new conductive opacities for the liquid
metal (Itoh et al 1983, ApJ, 273, 774) and crystalline lattice
(Itoh et al. 1984, ApJ, 285, 758). The envelopes contain
reasonable approximations to the expected diffusion profiles, and
the thermodynamic quantities are interpolated using the additive
Recent additions allow this code to compute smoother quantities
needed for pulsation calculations and it also computes the Modified
Ledoux term for the Brunt-Vaisala frequency.
To download the code click here
then gunzip and untar it by
% gunzip wdcode.tar.gz
% tar xvf wdcode.tar
The tar file should create a directory "evol" containing
AUXIN5 EEOSHE IEOSO SQOPACDB temperatures.con
AUXIN5DB EEOSHE.nor masses sqopac wdxdfitdb.f
EEOSC EEOSHE3 Makefile sqopacdb
EEOSH IEOSC SQOPAC
The compilation is done as follows: (You have to be in the evol directory)
% make wdxdfitdb
which creates an executable file wdxdfitdb. Note that you need fort77 and f2c
compilers to compile this code. These compilers are installed on the Unix
machines (ugrad machines) but not on astro.
You need an input file to run wdxdfitdb, and you need to specify the temperature
in temperatures.con file. I have already changed it to 4000. so that you don't
need to modify this file for the assignment. We'll calculate evolutionary models
down to T=4000 K
Fortunately, we have necessary input files for different masses in the "masses"
directory (Thanks to Travis, Don's former student). All you need to do is to
copy input files for whatever mass you need.
Let's help Spinal Tap with their first model calculations (DA with 0.45 solar mass)
any questions: please e-mail firstname.lastname@example.org
First copy the input file from masses directory by typing
% cp masses/M=0.450 M450204.mod
45 means 0.45 Msun, 02 is for the He, and 04 is for the H fraction. You can give
any name you like.
Then we'll edit this file to change the He and H abundance of the WD.
The first 14 lines of this input file are:
modelt1 <---- Name for summary output
modelt6 <--- Name for envelope parameter file
modelt9 <--- Name for model summaries (create new models from these)
model.out <--- Copy of screen output
model.log <--- Log file with extra info that can tell you what's going on
modelt40 <--- output file for pretty pictures
modelt50 <--- Output models for pulsation
3 .15 3 1 1
0.e-04 0.e-02 5 -1.25 3. -3. <--- amhyhe amheca alfa(1) (2) (3) (4)
-1 -1 1 100 20 1 1 3 -1 100 1 1
0.32951847e 02 <--- Mass in cgs units. (nevermind)
amhyhe - Mass of hydrogen layer in stellar mass units.
amheca - Mass of helium layer in stellar mass units.
alfa(1) - Diffusion exponent for H-rich part of H/He transition zone.
alfa(2) - Diffusion exponent for He-rich part of H/He transition zone.
alfa(3) - Diffusion exponent for He-rich part of He/C transition zone.
alfa(4) - Diffusion exponent for C-rich part of He/C transition zone.
All we need to do is to change H and He abundance of the input file. Therefore,
if you want to calculate a DA model with 10^-4 H and 10^-2 He, change the first
two parameters of the 10th line to
and save this input file.
% wdxdfitdb < M450204.mod
ps: if you type this, and you see the error :
wdxdfitdb: Command not found
that means your path is not defined correctly, just type
% ./wdxdfitdb < M450204.mod
and you're done!
The output files from wdxdfitdb are:
modelt1, modelt6, modelt9, model.out, model.log, modelt40, modelt50.
Explanations for these outputs are given here.
The most important
output file is the first one, modelt1.
It has the form:
56 6.3607E+09 22.704 6.231 6.190 9.002 3.609259 -4.2975 -10.0000 .590
The colums are as follows:
model #, Age (yrs), log P_c (central pressure), log T_c, log rho_c (density), log R (radius), log T_eff, log L/Lsun, log Lneutrino/Lsun, M_crys/M_star (crystallized mass fraction.
Last modified 12 November 2001