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Special BAT FITS Keywords

1. Overview:

This thread gives a summary of the special keywords used by BAT software for analysis.

Read this thread if you want to: Know which keywords are used by BAT software

Last update: 2007-01-30

2. Keywords Used

The BAT software uses FITS keywords to both document the analysis procedures used, and to pass information to downstream tasks. This section lists those keywords, how they are created and used, and by what tasks.

• ACOLAPP - a boolean keyword indicating whether the autocollimation correction has been applied to the image plate scale. Set by: batfftimage. Used by: none.

• BACKAPP - a boolean keyword which indicates whether the BAT background has been subtracted. This can mean some form of explicit subtraction, or automatic subtraction via the mask-weighting/imaging approaches. Set by: batfftimage,batbinevt. Used by: batclean.

• BALAPP - a boolean keyword indicating whether fine-level balancing has been performed on a detector image. Set by: batclean. Used by: NONE

• BAT_{X,Y,Z}OBJ - floating point keywords which indicate where in the BAT field of view the source is located. The coordinate system is the BAT coordinate system, and the units are centimeters. Objects at at infinity are placed at 10 km. Set by: batmaskwtevt, batmaskwtimg, batupdatephakw. Used by: batcelldetect, batdrmgen.

• BAT_RA, BAT_DEC - floating point keywords which indicate where on the sky the source is located (celestial RA and Dec). Set by: batmaskwtevt, batmaskwtimg. Used by: NONE.

• CLEANLEV - an integer keyword indicating the number of iterations of cleaning have been performed. Set by: batclean. Used by: batclean.

• DISTAPP - a boolean keyword indicating whether the image, mask weights, or source detection results have been adjusted for non-linear image distortion effects. Set by: batcelldetect, batwarpimg, batmaskwtevt, batmaskwtimg. Used by: batwarpimg, batcelldetect.

• FFAPP - a boolean keyword indicating whether the image, mask weights or fluxes have been corrected for geometric projection effects. Set by: batfftimage, batmaskwtimg, batmaskwtevt. Used by: NONE.

• FLUXMETH - a string keyword which indicates what kind of flux extraction method was used. Allowed values are 'RAW' (pure unsubtracted counts); or 'WEIGHTED' (mask-weighted light curve or image = background-subtracted). Set by: batfftimage,batbinevt. Used by: batdrmgen.

• GAINAPP - a boolean keyword indicating whether BAT energy calibration has been applied. Set by: bateconvert, baterebin. Used by: bateconvert, batdrmgen.

• GAINMETH - a string keyword indicating what kind of BAT energy calibration was performed. Allowed values are: 'LINEAR' (linear ADU to energy conversion); QUADRATIC (quadratic ADU to energy conversion); 'CUBIC' (cubic ADU to energy conversion); 'DIRECTCUBIC' (obsolete); 'FIXEDDAC' (cubic ADU to energy conversion at fixed DAC level). Set by: bateconvert, baterebin. Used by: batdrmgen, baterebin.

• IMATYPE - a string indicating the type of image produced. Allowed values are: 'INTENSITY' (rate map); 'EXPOSURE' (partial coding / vignetting map); 'SIGNIFICANCE' (signal-to-noise map); 'BACKGROUND' (mean background map); 'VARIANCE' (variance map); 'ERROR' (standard deviation map). Set by: batfftimage, batcelldetect. Used by: NONE.

• MSKWTAPP - a boolean keyword indicating whether the image, mask weights or fluxes have been normalized by the efficiency of the mask weighting algorithm. Set by: batfftimage, batmaskwtimg, batmaskwtevt. Used by: NONE.

• MSKWTSQF - a floating point keyword recording the half-variance of the mask weights. Set by: batfftimage, batmaskwtimg, batmaskwtevt, batupdatephakw. Used by: batdrmgen.

• NGOODPIX - an integer keyword recording the number of enabled detectors (pixels). Set by: batfftimage, batmaskwtimg, batmaskwtevt, batupdatephakw. Used by: NONE.

• NGPIXAPP - a boolean keyword indicating whether the image, mask weights or fluxes have been normalized by the number of enabled detectors. Set by: batfftimage, batmaskwtimg, batmaskwtevt. Used by: NONE.

• OVERSMP{X,Y} - an integer keyword recording the oversampling factor used in the image in the BAT_X and BAT_Y directions. Set by: batfftimage. Used by: batcelldetect.

• OCCAPP - a boolean keyword indicating whether the image has been corrected for occultation by the earth, moon or sun. Set by: batoccultmap. Used by: batoccultmap.

• OCCTYPE - a string keyword indicating how the image was corrected for occultation. Allowed values: 'DIVIDE' if the image was divided by the fractional exposure; 'MULTIPLY' if the image was multiplied by the fractional exposure. Set by: batoccultmap. Used by: NONE.

• PCODEAPP - a boolean keyword indicating whether the image, mask weights, or fluxes have been corrected for partial coding. Set by: batfftimage, batmaskwtimg, batmaskwtevt. Used by: NONE.

• PCODEFR - a floating point keyword recording the partial coding fraction for a given source in the BAT field of view (a number between zero and one). Set by: batmaskwtevt, batmaskwtimg, batupdatephakw. Used by: NONE

In addition to the tasks listed above, it is also common for FTOOLs tasks to transfer existing keywords from the input file to the output file, so it is possible for the keywords to appear in other outputs than described.

3. Data Types

BAT software uses and creates various data types.

4. Modifications

• 2005-12-04 - first revision

• 2006-04-12 - formatting changes

• 2006-05-26 - addition of DISTAPP

• 2007-01-30 - change table formatting slightly