lte-codes sterne spectrum ffit sfit grids idlines
commands idlines


Simon Jeffery, Armagh Observatory

Helium and Nitrogen lines in spectrum of V652 Her

Observed (black) and theoretical (red) spectrum for V652 Her. The spectra are shown at full scale and at 5x magnification. Helium and Nitrogen lines with theoretical equivalent widths greater than 10 mÅ are identified at the top. At the bottom, the relative strengths of all lines are plotted schematically, for each element present in the model.


An IDL procedure to display a region of spectrum, optionally with a model superimposed on the observations, together with the positions of selected lines.
Positions of lines in common atomic spectra are marked in the lower panel in logarithmic form. Lines of selected atoms are identified against the observed spectrum and fit.


IDL> idlines, specfile, linelist, xlo, xhi, xr, atoms, [thresh, [rv], [Keywords]


<specfile> - character string - name of file containing spectrum (and fit) assumed to be x,y file with 3-line header
<linelist> - character string - name of file containing eq.widths assumed to be 'spectrum' output
<xlo> - real variable - lower limit of plot
<xhi> - real variable - upper limit of plot
<xr> - real variable - xrange to show in each panel of plot
<atoms> - integer vector - atomic numbers of spectra to be identified
<thresh> - real variable - threshold eq width to identify lines (Angstrom)
<rv> - real variable - radial velocity of spectrum (km/s) (Use this to match line-ids to observed positions).


/FIT - overplot the fit
/EW - read and select the lines using equivalent widths
/NF - read and select the lines using n*gf (central opacities)
/ALL - plot individual atomic spectra schematically
/MULT - add multiplet labels to line ids
/STIS - to allow for air/vacuum shift at 2000A
/XTEND - extend line identification marks (useful in some cases)
/XPAND - expand plot by factor of 5
/DUPLEX - plot two regions of spectrum on the same panel (overridden by /ALL)
/PRINT - plot hardcopy as a postscript file

Hint: To obtain a nice display
IDL> window,xsize=1024,ysize=600

Input Files


sp2: single spectrum (could be observed or model)

sfit: observed spectrum and model fit sfit output file containing observation and solution. Keyword /FIT must be specified


lte_lines These linelists contain no information about relative line strengths, but can be used for inspection of data independent of any models. Many of the linelists in this format contain information about Moore multiplet numbers, and these can be added to the plot using the keyword /MULT.
The linelist is read in assuming this format by default -- i.e. if neither keyword /NF or /EW is supplied.

/NF: <linelist.used> These linelists are generated by SPECTRUM immediately after a linelist and model atmosphere are read in. This type of linelist can also be read assuming default options.
However, the final column contains the product of the lower level population * the gf-value at optical depth tau ~ 0.1 -- thus giving an approximate indication of the line strength (neglecting all line-broadening). This can be used to select the lines identified using a parameter thresh (see argument list). To do this, the keyword /NF must be supplied.

/EW: <linelist.eqwid> The function calc_lines in SPECTRUM produces a file containing equivalent widths for all lines in the atomica data input list, with user-specified abundances. The file format is significantly different from the above two formats, so cannot be read unless the keyword /EW is also supplied (at present). The number of lines identified can be changed by adjusting the threshold parameter


The datafiles required to run each example are provided with the distribution, but can also be downloaded from here.

1. Simple line matching

bd13_rmax.sp2 - spectrum of V652 Her at max radius
lines_woolf.d_USED - list of lines preselected for synthesis, with strengths as produced by SFIT

IDL> print,' Identify all Si,P,S lines in a spectrum '
IDL> idlines, 'bd13_rmax.sp2', 'lines_woolf.d_USED', 4200, 5000, 100, [14,15,16], 0.1, 0

IDL> print,' Identify Si,P,S lines with n*gf > 0.1 in a spectrum (do not plot any fit) '
IDL> idlines, 'bd13_rmax.sp2', 'lines_woolf.d_USED', 4200, 5000, 100, [14,15,16], 0.1, 0, /NF

2. Comparing equivalent widths - spectrum of V652 her at max radius, with model fit as produced by SFIT
bd13_synth_lines.dat - list of lines and equiv widths for above fit, as produced by SPECTRUM

IDL> print,' Identify C,N,O lines having ew > 10 mA in spectrum with a fit '
IDL> idlines, '', 'bd13_synth_lines.dat', 4200, 5000, 100, [6,7,8], 0.010, /FIT, /EW

IDL> print,' As above with hard copy saved as'
IDL> idlines, '', 'bd13_synth_lines.dat', 4200, 5000, 100, [6,7,8], 0.010, /FIT, /EW, /PRINT

3. Optical spectrum including heavy atoms - optical spectrum of PG 1219+534, with model fit produced by SFIT (3900-5100 A)
opt_lines.000 - list of lines preselected for synthesis, with equivalent as produced by SFIT

IDL> idlines,'','opt_lines.000',4000,5000,100,[2,6,7,8,13,14,15,26,28],0.005,-46.6, /FIT, /EW
IDL> idlines,'','opt_lines.000',4000,5000,100,[2,6,7,8,13,14,15,26,28],0.005,-46.6, /FIT, /EW, /DUP

4. uv spectrum with correction for lambda_vac - ultraviolet (STIS) spectrum of PG 1219+534, with model fit produced by SFIT (2200-2400 A)
stis_lines.000 - list of lines preselected for synthesis, with equivalent as produced by SFIT

IDL> idlines,'','stis_lines.000',2200,2400,10,indgen(30),0.001,-58.7, /FIT, /EW, /STIS

Note the use of indgen to generate an integer array for the atomic identifiers. This example will plot all atoms with X≤30

Example Output - Plot generated using the above input files and the final example given below.

IDL procedures for plotting spectra and line identifiers

idlines : plot map of spectrum with lines by central intensity

readspec : read spectrum from 2 column x-y file with 3 line header

readspecfit : read spectrum and fit from 4 column file with " " "

plotspec : plot a spectrum onto a new frame

readlist : read linelist in lte-lines format

marklist : marks all lines in linelist

markion : marks positions, identities and wavelengths of given ion

markspec : marks positions and strengths of spectral lines from a given element

markeqwid : marks positions and eq wids of spectral lines from a given element

For additional routines, see also



A tarball containing all the idlines procedures and examples can be found here: idlines.tgz.

Bugs and Future Development

This program started (as usual) as a simple hack. It has acquired increased functionality, and thus an increased potential for catastrophic bugs. Ideally, the data input should be more intelligent -- so that the software will recognise the specified format and set the keywords accordingly. It would also be handy to be able to supply the spectrum and/or model as arguments on the command line. Writing a full blown widget is left to an enterprising young programmer! Please send bug reports and suggestions for "simple" improvements to the author.

This page is maintained by:
Simon Jeffery
Last modified: Tue Apr 28 11:03:50 BST 2009