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SYNOW (SYnthetic NOW)



SYNOW 1.0

Control of the available parameters is accomplished through a namelist input file, the "in.dat" file. An in.dat file has the following format:

 

$params
   vphot    =  4000.0
   vmax     = 40000.0
   tbb      = 15000.0
   ea       =  4000.0
   eb       =  8000.0
   nlam     =    1000
   flambda  = .false.
   taumin   =    0.01
   grid     =      32
   zeta     =     1.0
   stspec   =  3500.0
   pwrlaw   = .false.
   pwrlawin =     8.0

   numref   =       2

   an       =     1,     2,    16,     6
   ai       =     0,     1,     1,     1
   tau1     =  5.00,  0.00,  0.10,  0.10
   vmine    =  2.00,  2.00,  2.00, 20.00
   vmaxe    = 40.00, 40.00, 30.00, 30.00
   ve       =  3.00,  3.00,  3.00,  3.00
   temp     = 13.00, 13.00, 13.00, 13.00

$END


Parameters in in.dat

  • vphot - Velocity at photosphere in km/s. The photosphere is a sharply definded sphere, providing continuum radiation at the bottom of the envelope.

  • vmax - An artificially imposed upper boundary on the envelope in km/s. Usually set to a value where the optical depths in all lines is probably negligible.

  • tbb - Blackbody temperature in K. The continuum emitted from the photosphere is characterized by this temperature.

  • ea - The lowest wavelength to be considered, in Angstroms. Your plot may actually start at a higher wavelength, because of the stspec parameter below.

  • eb - The highest wavelength to be plotted in Angstroms.

  • nlam - Number of wavelength points where the spectrum is computed.

  • flambda - Make the output flambda vs lamba instead of fnu vs lambda if set to .true.

  • taumin - Minimum line optical depth to select. The presence of a species in the envelope is set by a nonzero optical depth in a reference line of the species (usually the strongest optical line). All other line optical depths are determined relative to that reference optical depth assuming Boltzmann excitation. The taumin parameter sets a lower optical depth threshold. If a line is computed to have optical depth below taumin, it is not included in the line list for the calculation. If many attempts are needed to get major features to fit, taumin can be set to a high value. It just makes Synow only consider stronger lines.

  • grid - Grid resolution. This number controls the number of radial points used in the calculation, and actually represents the radius of the photosphere in grid points. This number can be as high as 35, but probably no lower than 5. Higher values of grid provide better spatial resolution when computing the spectrum and source functions, but also slow down the program.

  • zeta - Set to something less than 1 to get a diluted blackbody. We've never used anything besides 1.

  • stspec - Place to start actually computing the spectrum. This should be higher than the value of ea, by something like 500 angstroms or so.

Running Synow


When you run synow, you will get the follwoing output to STDOUT. 
 $synow
 INITIALIZING
 INITIALIZATION COMPLETE FOR   1 SPECIES
 ON FILE   6 of  9
 ON FILE   7 of  9
 ON FILE   8 of  9 
 ON FILE   9 of  9
 ALMOST DONE
 $
  • pwrlaw - Optical depth in all lines is deployed spatially according to one or two laws. One of them is a powe r-law radial density gradient. If this parameter is set to .true., then the optical depth in the lines will fall off with radius according to a power law with index pwrlawin.

  • pwrlawin - The power law index if optical depths in lines are to fall off like a power law.

  • numref - The number of reference optical depths (ions) that will be specified at the end of the file.

  • an - Atomic numbers of species to include in the calculation.

  • ai - Ionization stages of species included ( 0 = neutral, 1 = first ionization, etc, up to ai = 5).

  • tau1 - Optical depth in the reference line of the corresponding (an, ai) ion at vphot. Usually the reference l ine of an ion is the strongest optical line of that ion. So for H I it is H-alpha 6563. The optical depth in this line at all radii is determined by the choice of powerlaw-falloff or exponential-falloff. All other lines of this ion have optic al depths determined relative to the reference line, assuming Boltzmann excitation.

  • vmine - Lowest velocity in the envelope where the (an, ai) ion is present. If vmine > vphot, tau1 is *not* the optical depth in the line at vmine, it is *lower*. If vmine >, we say the ion is "detached" from the pho tosphere. Units are in 1000s of km/s.

  • vmaxe - Highest velocity in the envelope where the (an, ai) ion is present. Units are in 1000s of km/s.
  • ve - If pwrlaw is set to .false., then the optical depths of the lines are assumed to fall off exponentially. Each individual line is allowed to have its own e-folding length (which is ve for tha an, ai ion). The units of ve are in 1000s of km/s.

  • temp - Excitation temperature of the ion in 1000s of K. This temperature is the tempreature used to determine all lines relative to the reference line, assuming Boltzmann excitation.
The in.dat in presented on this page is the one used. Note that numref was set to 2, but here it says that 1 species was initialized. That is because the He II we included we set to have optical depth zero in its reference line at the photosphere. So Synow ignored it. Also not that we had two other ions in our an, ai list. They were S II and C II. But since we set numref to 2, they were ignored.

The in.dat in the introduction is the one used. Note that there, numref was set to 2, but here it says that 1 species was initialized. That is because the He II we included we set to have optical depth zero in its reference line at the photosphere. So SYNOW ignored it. Also note that we had two other ions in our an, ai list. They were S II and C II. But since we set numref to 2, they were ignored.

The ``files'' that SYNOW is talking about are line list files. The Kurucz linelist has been stored on disk on our network for special use with SYNOW in a highly compact form. If your simulation will take into account a lot of lines, your code will run slower, but should still take at most only a few minutes. For a spectrum with only a few lines, you don't even have time for a sip of coffee.

The actual output spectrum of synow is placed into the file called ``fort.11'' which is created by SYNOW each time it runs. Make sure not to overwrite it! After running SYNOW, you can look at fort.11 using some tool like xmgrace or gnuplot. The first two columns are the important ones. The last one is just the blackbody spectrum of the photosphere.

A good idea is to write a shell script to keep track of old in.dat files, and corresponding fort.11 files. Often, a real SN spectrum is plotted over a synthetic SYNOW spectrum, and repeated adjustments are made to the in.dat file until the spectra match. This is kind of an art.