Read in one or more auxiliary response files (ARF). An ARF gives area versus energy and is used to modify the response matrix for a data set. The file must be in the OGIP standard format.
XSPEC> arf [<filespec>...]
where <filespec> =:: [<data set num>] <filename>... and where <filename> is the name of the auxiliary response file to be used with the associated data set. <data set num> is the data set number for the first <filename> specified, <data set num> plus one is the data set number for the next file, and so on. If no <data set num> is given in the first <filespec> it is assumed to be 1. If no file specifications are entered, then none of the data set responses are modified. An error message is printed if the data set number is greater than the current number of data sets (as determined from the last use of the data command). A file name none indicates that no auxiliary response is to be used for that data set. No auxiliary response means that any incident spectrum will produce no counts for those particular channels. If a file is not found or cannot be opened for input, then the user is prompted for a replacement auxiliary response file. An <EOF> at this point is equivalent to none. See the data command for ways to completely remove the dataset from consideration.