8.5.2 Rectangular Extractions

  For rectangular extractions of either IUESIPS or NEWSIPS data, you may use the routine BOXCAR. For those who remember the older programs EXMELO and MAKEMELO, BOXCAR is capable of both returning the new extracted spectrum and writing it to an output file. For IUESIPS the ability to write a new MELO file is preserved. For both IUESIPS and NEWSIPS, a FITS file containing the new spectrum may be written. In addition to the old median/mean background smoothing, there is the option of fitting the background with a Chebyshev polynomial, as is done to create the background vector in MXLO files.

The calling sequence for BOXCAR is as follows:

BOXCAR,IMAGET,object,bckgd,h,w,g,b,n,f,q,/extended,/small, $
medianw=medianw,meanw=meanw,expt=expt,/melo,/fits,/chebyshev 

IMAGET	Line-by-line file to read.
object	Normally this is a two element vector giving the range of lines containing the object slit, inclusive. To use default values, enter 0. If a single positive value is entered, it is considered to be the central line of the spectrum and a default width is used. If it has more than two elements, these EXACT lines will be extracted.
bckgd	Normally this is a four element vector giving the ranges for the two background swaths. If there are more than four elements, only those particular background lines will be used.
h	If the input file is a SILO file, or if the user elects to write a FITS file via the FITS keyword, H will be the FITS header. Otherwise, it is the IUESIPS ``scale factor'' record.
w	Wavelengths.
g	Gross fluxes (coadded lines specified by the OBJECT parameter).
b	Background fluxes (scaled coadded background lines).
n	Net fluxes (G - B).
f	Calibrated fluxes.
q	Quality flags ($\nu$ flags in the object slit for each wavelength are coalesced for NEWSIPS data; for IUESIPS data the minimum $\epsilon$ flag in the object slit is kept).
extended	If this keyword is set, and the object slit was not specified, default values appropriate for an extended object will be used.
small	If this keyword is set, and the object slit was not specified, default values appropriate for the small aperture will be used.
medianw	Median filter width, if this smoothing is desired for the background.
meanw	Mean filter width, if this smoothing is desired for the background.
chebyshev	If this keyword is set, the background will be fitted with a sixth order Chebyshev polynomial.
expt	Exposure time in seconds, for calibrating IUESIPS data. If not given, h(39:41) will be used.
melo	For IUESIPS data, the calculated spectrum will be written to a to a file in the usual MELO format (.DAT and .LAB files).
fits	If set, a FITS file containing the output spectrum will be written. IUESIPS ``h'' vectors will be converted to FITS headers. The program will prompt for the usual items requested by IUESPEC if the appropriate entries are missing from the ``h'' vector. See section 8.5.1 for an example of how to read this FITS file.

For IUESIPS data BOXCAR returns data that is calibrated (as EXMELO did) but the exposure time can be entered via the EXPT keyword. However, the full range of corrections done by IUESPEC (e.g., THDA correction, LWR sensitivity correction) will be done if the user wishes to write out a FITS file. It is possible to write both a MELO file and a FITS file; the FITS file is written second and the ``H'' parameter returned will be the FITS header. NEWSIPS data are calibrated via the procedure NEWCALIB.

Slits for SILO files are based on the assumed regions that SWET (Signal Weighted Extraction Technique) uses when the MXLO file is created. Slits for ELBL/LBLS/ESSR files are based on the defaults used in the older program EXMELO. Median and Mean filters are based on those used by EXMELO (note that ESSR files have fewer samples and therefore they have smaller filter values). See Table 8.2 for a list of default parameters for various line-by-line files. See Table 8.3 for a description of line-by-line file types.

 

SILO Small 25 [19,31] [11,17,33,39] 13 7 8 ce 1 1

SILO Large point 51 [45,57] [32,38,64,70] 13 7 13 ce 1 1

SILO Large extended 51 [40,63] [32,38,64,70] 23 7 13 ce 1 1

ELBL Small 55 [47,64] [35,44,67,76] 18 10 16 cc 63 31

ELBL Large point 55 [47,64] [29,38,73,82] 18 10 22 cc 63 31

ELBL Large extended 55 [41,70] [29,38,73,82] 30 10 22 cc 63 31

LBLS Small 28 [24,32] [18,22,34,38] 9 5 8 cc 63 31

LBLS Large point 28 [24,32] [15,19,37,41] 9 5 11 cc 63 31

LBLS Large extended 28 [21,35] [15,19,37,41] 15 5 11 cc 63 31

ESSR Small 28 [24,32] [18,22,34,38] 9 5 8 cc 31 15

ESSR Large point 28 [24,32] [15,19,37,41] 9 5 11 cc 31 15

ESSR Large extended 28 [21,35] [15,19,37,41] 15 5 11 cc 31 15 Distances: CC is measured from object center to background center.                       CE is measured from object center to background edge.

 

SILO NEWSIPS 80 <640 present present

ELBL IUESIPS 110 <1022 01-Oct-85 present present

LBLS IUESIPS 55 <1022 04-Nov-80 01-Oct-85

ESSR IUESIPS 55 <600 22-May-78 04-Nov-80 14-Jun-78 10-Mar-81

IUESIPS 32 <600 03-Apr-78 22-May-78 17-Apr-78 14-Jun-78 Dates for ESSR (``Extracted Spectrum, Spatially Resolved'') files (and earlier) are taken from Turnrose, Thompson, & Gass, IUE NASA Newsletter 25.