The SWIFT BAT Software Guide Version 6.3 30 ... - HEASARC - Nasa

D.2. BATCELLDETECT 113
in instrumental sky coordinates, and are meant to be interpolated to the desired sampling.
The WCS keywords must specify the image coordinate systems.
(keepbits = “ALL”) [string ]
Integer number of bits of precision to keep in the output images. A value of ALL means
keep all bits. A positive value indicates that ‘keepbits’ bits of precision should be preserved,
and the other bits should be set to zero. Fewer kept bits means the output images are more
compressible, at the expense of lost precision. For background and variance maps, a straight
number of bits are kept (thus preserving the same relative precision across the map). For
significance maps, ‘keepbits’ prescribes the number ofnoise bits to keep; more bits may be
kept if a pixel is significantly above the noise (thus preserving the same noise quantization
error across the map).
(npixthresh=20) [integer ]
Minimum number of pixels in the background window to enable source detection. Setting this
parameter to a high number will prevent detections based on only a few background pixels.
(posfitwindow=0) [real ]
The position ‘window’ radius, in degrees, used for all position fits, including known sources.
The window is the allowed region over which the centroid position is allowed to vary during the
position fit, regardless of the error radius specified for the source. Typically, this parameter
will only be used if the attitude solution is suspected to be incorrect. A value of zero indicates
that the window size is determined by the error radius specified in the catalog, if any. This
parameter is basically an override for the ERR RAD column. See “Fitting For Position and
Flux” above.
(possyserr=0) [real ]
Systematic position error, in degrees, to be added in quadrature to each position error radius
reported in the output catalog. This parameter allows one to specify a minimum systematic
position error for every reported detection (which is separate from posfitwindow, which
controls the position determination process itself).
(keepkeywords=“*APP,CLEANLEV”) [string ]
A comma separated list of keywords or keyword wildcard patterns. The matching keywords
are transferred to the output catalog, under a column of the same name. This is a way
to automatically keep track of corrections that have been applied to the input image. The
CFITSIO wildcard patterns are: ‘?’ will match any single character at that position in the
keyword name; ‘*’ will match any length (including zero) string of characters; and ‘#’ will
match any consecutive string of decimal digits (0 - 9).
(hduclasses=”-VIGNETTING,-BKG VARIANCE,-BKG STDDEV,-SIGNIFICANCE”) [string
]
List of comma-separated image type filters, used to accept or reject images based on their
HDUCLASn keywords. This is useful for files that contain different kinds of image extensions.
A minus sign “-” indicates exclusion. Each image is checked for each of the HDUCLASn
keywords. If any of the keyword values matches an excluded list member, then that image is
rejected for analysis. List members without a minus sign must be present. A value of NONE
indicates no filtering (i.e. all images are accepted).
(sortcolumns=“-KNOWN,-SNR/UNKNOWN,RA OBJ”) [string ]