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9 Low-Dispersion Flux Extraction (SWET)

 

Spectral data are extracted from the two-dimensional (2-D) low-dispersion resampled images (SI) using a signal weighted extraction technique (SWET). This technique provides an increase in the signal-to-noise ratio (S/N) of the extracted spectrum, as compared to simple ``boxcar'' extractions, by utilizing information on the cross-dispersion spectral profile, while preserving the total flux. The output of this technique also includes an error estimate associated with each point in the extracted spectrum and cosmic ray hits are, in many cases, automatically rejected from the calculation of extracted fluxes. The technique, which has been developed for low-dispersion IUE data, is based on the weighted slit extraction code originally developed by Horne (1986) for use with optical CCD data. A detailed explanation of the adaptation of this software for use with IUE data processed using IUESIPS is given by Kinney et al., (1991) who supplied the software to the IUE Project. Various threshold values in the code were modified by the IUE Project to account for the very different flux scales of NEWSIPS and IUESIPS.

Briefly, the processing steps involved in the weighted extraction of a one-dimensional (1-D) spectrum from the low-dispersion SI are as follows:



 
next up previous contents
Next: 9.1 Noise Models Up: No Title Previous: 8.4.2 High-Dispersion
Karen Levay
12/4/1997