% @(#)width_tsa.hlq	19.1 (ESO-IPG) 02/25/03 13:32:46
%+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 
%.COPYRIGHT (c) 1992 European Southern Observatory & Copernicus Astron. Center%.IDENT     width_tsa.hlq
%.AUTHOR    Alex Schwarzenberg-Czerny, ESO & Copernicus Astronomical Center 
%.KEYWORD   MIDAS, help files, WIDTH/TSA
%.LANGUAGE  LATEX
%.PURPOSE   Evaluate line width and profile
%.VERSION   0.0               June 1992
%.RETURNS   None  
%.ENVIRON   TSA context
%------------------------------------------------------------------------------
\se
SECTION./TSA
\es\co
WIDTH/TSA                                 15-SEPT-1992 A. Schwarzenberg-Czerny
\oc\su
WIDTH/TSA inima [width] [centre]     Evaluate line width and profile
\us\pu
Purpose: 
           This command finds the strongest line in the frequency band
           of 'centre'+/-'width'/2 and determines its characteristics,
           by fitting its profile, among others. The profile used at the 
           moment is a cosine bell. The same band is used to find the 
           continuum level, so it shouldn't be too narrow. The STARTTSA 
           keyword is set to the line centre frequency and OUTPUTD
           returns width and level values, as listed.
\up\sy
Syntax: 
           WIDTH/TSA inima [width] [centre]
\ys\pa
           inima = name of input frame, it must contain a periodogramme
               in its first row, in DOUBLE PRECISION.
\ap\pa
           width = full width of the frequency band searched for the 
               strongest line to be measured, in units of frequency.
               Default - the whole periodogramme. Note  that this band
               is used to define the continuum, so should not be too narrow.
               However, a too broad band causes time loss on determination 
               of the continuum level.
\ap\pa
           centre = central frequency of the band searched for the strongest
               line to be measured. Default - the centre of the periodogramme.
\ap\sa
See also:
           SHOW/TSA, POWER/TSA, AOV/TSA, SCARGLE/TSA
\as\no
Note: 
           You input the f u l l width of the frequency band, while the command
           prints h a l f widths of the line, sort of a frequency error
           estimate. The error of central frequency fit tells only how well
           the theoretical profile fits the line and by no means constitutes
           an estimate of accuracy of line frequency. 
\\
           Note that the formal errors of the fit are multiplied by the square
           root of the number of periodogramme points falling within one
           half width of the line. This takes care of a possible correlation of the
           residuals (same sign) over that width, and so provides a more
           meaningful error estimate than usual least squares.
\\
           Do not unnecessary run the command over intervals containing
           too many points, since than it becomes slow. Use plot/row
           to identify the frequency of the line.
\on\exs
Examples:
\ex
           WIDTH/TSA PERIODG 1 23
           analyse a line centred around frequency 23
\xe\ex
           WIDTH/TSA PERIODG 
           analyse the strongest line in the whole spectrum.
           However, the line width estimation could be quite slow in this case.
\xe\sxe
