Last modified: December 2022

AHELP for CIAO 4.15


Context: Tools::Gratings


Straighten LETG/HRC-S spectra by applying tg_d adjustments.


dewiggle infile outfile


dewiggle reads in a standard LETG/HRC-S evt2 file and adjusts the TG_D values of all events to remove small "wiggles" and straighten the dispersed spectrum. The adjustments, which are up to +/-1.5 HRC pixels, are applied on a tap-by-tap (CRSV) basis along the dispersion axis and correct small residual errors that cannot be corrected by the HRC-S degapping procedure. Only TG_D values are affected; the output file will not exhibit any changes if displayed in sky or detector coordinates.

dewiggle is generally used in combination with the detilt and symmetrize commands--also contributed software tools--to prepare LETG/HRC-S spectra so that narrower spectral extraction regions can be used to improve the S/N of low-S/N data.


dewiggle input_evt2.fits output_evt2.fits clobber+

Run the program with the clobber parameter enabled.


name type ftype def min max reqd stacks
infile file         yes no
outfile file output       yes no
wfile file   ${ASCDS_CONTRIB}/data/wigglecorrection.dat       no
verbose integer   0 0 5    
clobber boolean   no        

Detailed Parameter Descriptions

Parameter=infile (file required stacks=no)

Input FITS file event list with columns CHIP_ID, CHIPY and TG_D.

Parameter=outfile (file required filetype=output default= stacks=no)

Output FITS file event list with modified TG_D column.

Parameter=wfile (file default=${ASCDS_CONTRIB}/data/wigglecorrection.dat stacks=no)

Wiggle correction file, containing TG_D correction as a function of CRSV.

Parameter=verbose (integer default=0 min=0 max=5)

Tool chatter level

Controls the amount of information tool prints to the screen.

Parameter=clobber (boolean default=no)

Remove outfile if it already exists?

About Contributed Software

This tool is not an official part of the CIAO release but is made available as "contributed" software via the CIAO scripts page. Please see this page for installation instructions.


There are no known bugs for this tool.

See Also

simple_hist, simple_stats
combine_grating_spectra, detilt, dewiggle, dmtype2split, mktgresp, symmetrize, tg_bkg, tg_choose_method, tg_create_mask, tg_findzo, tg_resolve_events, tgdetect, tgdetect2, tgextract, tgextract2, tgidselectsrc, tgmask2reg, tgmatchsrc, tgsplit