% @(#)computlyma.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:16:05
% @(#)computlyma.hlq	8.1 (ESO-IPG) 11/28/94 10:28:13
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%.COPYRIGHT  (c)  1993 European Southern Observatory
%.IDENT      computlyma.hlq
%.AUTHOR     PB, IPG/ESO
%.KEYWORDS   MIDAS, help files, 
%.PURPOSE    On-line help file for the command: COMPUTE/LYMAN
%.VERSION    1.0  23-NOV-94 : Creation, PB
%----------------------------------------------------------------
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SECTION./LYMAN
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COMPUTE/LYMAN					      23-NOV-94  PB
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COMPUTE/LYMAN  linetab outspe [refspe] [option] [noise] 
       Computes a normalized synthetic spectrum from a list of absorption lines
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Purpose:    
            Computes a synthetic spectrum (normalized at unit flux)
	    from a list of absorption lines. A noise can be added.
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Syntax:     
            COMPUTE/LYMAN  linetab outspe [refspe] [option] [noise] 
 \\
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             linetab = table with the lines to be computed\\
                       The format is that used by FIT/LYMAN to save the results
		       of  the fitting procedures. At least columns ELEMENT, 
		       LAMCEN, COLDEN, B, BTUR must be defined (see FIT/LYMAN 
  		       manual for details)	                        
                       
 \\
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             outspe  =  table containing output spectrum 
 \\
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             refspe  = template spectrum, in the table format used by FIT/LYMAN
                       The table must contain the columns WAVE, FWHM, NORMFLUX,
 	 	       STDEV (the last two can be 0.). 
                       Default is the value of the keyword SPECTAB     
 \\
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             option  = A:  all lines are computed\\
                       L:  only Lyman series is computed\\
                       M: only "metal" (i.e. non-H) lines are computed
                       Default: A	
 \\
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             noise   = sig1,sig2,rangen\\
                       A noise can be  added to the spectrum , where:\\
		       sig1 is the stdev of a gaussian noise, which can 
		       simulate for the sky and read-out noise;\\
                       sig2 is the total stdev at the continuum level.\\
                       rangen is a seed for the random number generator, 
		       and must be a NEGATIVE INTEGER NUMBER.\\
                       The noise is scaled with the flux 
  		       according to the poisson formula: \\
                     stdev(flux) = sqrt (sig1^2 + (sig2^2 - sig1^2)*sqrt(flux))
 \\
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See also: 
            FIT/LYMAN,CONVERT/LYMAN
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Note:       
            1)  The spectrum is computed at the wavelengths specified in  the 
		WAVE column
            	and convolved  with the instrumental resolution defined in the
		FWHM column.
                Both the pixelsize and the FWHM may vary along the spectrum. 
		Gaps may exist.\\
   
            2) Atomic parameters are taken from the atompar table.
 \\
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Examples:
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            COMPUTE/LYMAN  line_lis sintspe refspe A 0,0.1,-475
            Computes a spectrum with wavelength  range and FWHM defined in  refspe
            and absorption lines defined in line_lis. A purely poissonian noise is added,
            the final S/N at the continuum level being 10.
             
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            COMPUTE/LYMAN  line_lis sintspe refspe A 0.004,0.1,-475 
            As before, but at the noise a gaussian noise is added.  
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