XMM-Newton Science Analysis System
evselect (evselect-3.71.1) [xmmsas_20211130_0941-20.0.0]
The filtering process is carried out on an event-by-event basis
controlled by user-specified selection criteria which take the form of a single
boolean expression. The expression can contain symbolic names of
“intrinsic” event attributes,
and numeric constants combined with logical and arithmetic operators and
functions. Events for which the expression does not evaluate to true
will be marked as invalid or discarded from the data set and shall not
be considered in the product extraction.
supports selections based on intrinsic event attributes.
These attributes are present in the input event list table as corresponding
columns, the names of which are to be used in the selection expression. This
group further falls into the following sub-categories:
- spatial selections in raw pixel (RAWX/RAWY), physical detector
(DETX/DETY) or sky pixel (X/Y) space, or indeed
in any spatial coordinate system (e.g. TELX/TELY). Special
pre-defined region shapes exists such as CIRCLE,
ELLIPSE, ANNULUS, BOX, POLYGON. Spatial
filtering with mask images is possible as well.
- Celestial coordinates (RA/DEC) are available for the
CIRCLE, BOX and ANNULUS shapes,
e.g. (RA,DEC) in CIRCLE(253.231,-2.052,0.0166)
or (RA,DEC) in BOX(121.234,23.456,0.125,0.125,0)
where all values are in units of degrees.
These values are pre-processed into sky pixels.
- A special construct IMAGE may be used to extract data from
a spatial region which is defined by non-zero pixels in a supplied
FITS image. This image may have axes in DETX/DETY coordinates or
in celestial coordinates. Any celestial image with standard WCS
header keywords and integer or boolean values is acceptable. Note that the coordinate system should be epoch 2000 (FK5), earlier 1950 epoch (FK4) images will give a significant offset.
This expression is pre-processed into a BOX, encompassing the
whole image logically ANDed with a MASK, e.g.
'(X,Y) in BOX(25000,25000,15000,15000,0) && MASK(myHSTimage.fits)'
- energy selections in the form of one or more interval specifications
in either PHA or PI space.
- time selections in the form of
- one or more interval specifications
- one or more Good Time Interval (GTI) files created with
or any other SAS tasks which creates GTI files
- any other event attributes which are present (e.g. PATTERNID,
or CCDID, or WAVELENGTH in case of RGS)
XMM-Newton SOC -- 2021-11-30