Read Me

COMPILING

The program should compile simply by typing 'make'. You need the GSL
(GNU Scientific Library, see http://www.gnu.org/software/gsl/ ).


NOTES

* Star positions in Einstein radii x=sqrt(4GM/c^2 Dd Dds/Ds)
* so far all stars have the same mass


EXAMPLE

After compilation, an example run (command line) would be

./causticfinder stars.txt critcaust.txt 2 0.0 -0.5

'stars.txt' is the file containing the stars, included in this directory
'critcaust.txt' is the output file
2 is the number of stars in stars.txt
1.2 is sigmac (if zero, gamma is reduced shear)
0.1 is gamma

The output file contains 4 columns with the x and y coordinates
of critical curves (columns 1 and 2) and caustic curves (columns
3 and 4). Currently 200 points are calculated for each segment on the
curves. This can be changed with the variable 'M' at the start of
the program.

[This particular critical curve & cautic pattern was discussed by
Schramm & Kayser 1987, A&A 174, 361.
http://adsabs.harvard.edu/abs/1987A%26A...174..361S ]


AUTHOR

Robert W. Schmidt <rschmidt@ari.uni-heidelberg.de>

  Address:

  Robert W. Schmidt
  Astronomisches Rechen-Institut
  Zentrum fuer Astronomie
  Moenchhofstr. 12-14
  69120 Heidelberg
  Germany