The standard spectral file consists of a FITS file with a number of
extensions. For imaging detectors the primary array can contain an
image of the region from which the spectrum was extracted.
Each PHA dataset is contained within a
However, each file may also include
a number of (optional) associated, additional extensions which contain the
detector- and observation-specific information required for
construction of the calibration data etc.
(i.e. describing how that PHA dataset was selected, housekeeping parameters
during the extraction etc. ).
The format of these extensions will also conform to OGIP standards.
It should be noted that none of the latter optional extensions
are strictly mandatory for specification of the PHA dataset,
and hence as an input to XSPEC.
Thus these extensions are not discussed in detail here, and if disk space
becomes a problem may be deleted by the user prior to using XSPEC.
However, it should be stressed that any analysis package may
require information in the GTI and Detector extensions when
and/or spectral/spatial analysis is to be performed.
Information from the Detector extension will also be required when
background modelling is to be performed.
Such complex, detector-specific tasks will be discussed individually
However, in most cases the XFLTXXXX keyword (discussed below) provides
an adequate description of the required information.
- a Good Time Interval (GTI) extension
- a Detector extension
- a (Selector) History extension
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Last modified: Thursday, 21-Oct-2021 12:50:38 EDT