Modify one or more of the files used in background subtraction.
XSPEC> backgrnd [<filespec>...]
where <filespec> =:: [<data set num>] <file name>...
and where <file name> is the name of the PHA file to be used for background
subtraction for the associated data set. <data set num> is the data set number
for the first <file name> in the specification, <data set num>+1 is the
number for the next file, and so on. If no <data set num> is given in the
first <filespec> it is assumed to be one (1).
If no file specifications are entered, then none of the data set backgrounds are
modified. An error message is printed if <data set num> is greater than the
current number of data sets (as determined from the last use of the d ata
command. A file name none indicates that no background subtraction is to be
performed for that data set. If a file is not found or cannot be opened for
input, then the user is prompted for a replacement background file. An <EOF>
at this point is equivalent to using none as the background. See the data
command for ways of removing the data set from consideration. The user also is
prompted for a replacement if the background file has a different number of
PHA channels than the associated data set. A warning will be printed out if
the background detector ID is different than that of the associated data set.
The current ignore status for channels is not affected by the bkgrnd command. (See the ignore and notify command).
Note that background files have the same format as the PHA files used for the data command.