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Description (alpha or linux)

Solve for T, log g, abundance, v sin i, R2/R1 for one or two stars by fitting model spectra to normalized (high-dispersion) spectra.

It may be necessary, particularly when running this code on the Armagh alphas, to increase the data limit on your current process. This can be achieved with:
> limit datasize 1048576 kbytes
> ulimits -aD (alpha) to see maximum values.
("sfit_synth" currently requires 582Mb of virtual memory.)

With input commands saved in a file (eg "sfit_input", the code is run simply by
> sfit < sfit_input

If the spectra to be fitted have a filename "star_spectrum", then the best fit spectrum will be written out, together with the renormalized input spectrum, to a file called "star_spectrum.fit".

Input file syntax

Commands

 Allowed group commands are: models - sets up model spectrum grid model2 
- sets up model spectrum grid for second star save_grid, save_grd2 - saves model 
grid as binary file read_grid, read_grd2 - reads model grid from binary file cmask 
- define regions to _include_ in continuum fit continuum - select continuum renormalization 
method normalize - single step renormalization with no change of test parameters 
parameters - initialize fit parameters data - input observational data mask - 
define regions to _exclude_ from fit using given weights method - select solution 
method solve - pursue solution - NEW - set - set specific parameters - NEW - show	
- show current values of specific or all parameters end - finish gracefully The 
binary file access commands take the following form: save_grid file read_grid 
file Allowed method subcommands are: amoeba - downhill simplex method - NEW -	
genetic - genetic algorithm range w1 w2 - wavelength range to include in fit tolerance 
- convergence criterion ... to be implemented levenburg-marquardt - not working 
chi-squared - surface only Allowed continuum subcommands are: polynomial np - 
np is order of polynomial filter gw - gw is FWHM of gaussian filter Allowed data 
subcommands are: folder name - name of folder containing data spectrum name - 
name of file containing spectrum sigma sig - mean standard error on data in 'spectrum' 
pamela name - name of file containing spectrum in pamela format ( x, y, s ) instrument 
fwhm - FWHM (A) of instrumental broadening drift dv - velocity drift (km/s) during 
exposure The models and model2 commands take the following format: n ! file format 
specifier Sterne/Spectrum:
title ! title for model grid
nt ng na ! dimensions of model grid (nT, ng, nHe)
ws we dw ! wavelength grid for internal storage model(1,1,1) ! list of files containing models
model(2,1,1)
model(3,1,1)
... model(5,5,5) The mask command takes the following format: n - number of mask regions ms me mw - start and end wavelength for mask and weight The cmask command takes the following format: n - number of mask regions ms me - start and end wavelength for mask


Example 1. Fit Teff, log g and n_H to WHT/UES spectrum using a grid of helium-rich model spectra.

Example 2. Setup model grid in binary form for subsequent use.

Example 3. Fit Teff_1, Teff_2 and radius ratio in binary, using saved model grids
This page is maintained by:
Simon Jeffery (csj@star.arm.ac.uk)
Last modified: June 2, 2003