White Dwarf Models

We will use the WD evolution code written by Martin Schwarzschild.
Subsequent modifications made by:
  Version         Author(s)
  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
  volume technique.
  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)

EXAMPLE

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 
2. 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. 1.
1. 1.
  0.32951847e 02  <--- Mass in cgs units. (nevermind)


where 
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

1.e-04 1.e-02 

and save this input file.

then type 

% 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!


OUTPUT FILES

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.