NAME
niswbkgspect - estimate NICER Space Weather background spectrum
USAGE
niswbkgspect infile outfile mkfile selfile
DESCRIPTION
The niswbkgspect task estimates a background file for a NICER
spectrum using the "space weather" model that is usable within XSPEC.
This background file is estimated using a set of NICER background events (derived
from observations of "blank" fields) based on the distribution of the KP
solar activity index, the cut-off rigidity (COR_SAX) and the SUN_ANGLE appropriate
to a given observation.
This task produces a constant background file containing an estimate
of the NICER background. This background file can be
subtracted from the NICER target spectrum within XSPEC.
Inputs
The required inputs to the task are
- Spectrum file (infile). This is the target spectrum for which you require
a background estimate. It should have an accurate GTI extension.
- Output file (outfile). This is the name of the output pha file containing
the background estimate.
- Filter file (mkfile). This is the filter file which should cover
the time range of the accumulated spectrum. I.e. the spectrum GTIs
and filter file times should overlap.
- File with FPM Selection information (selfile). This can be either
a cleaned event file with an FPMSEL extension, or the filter file.
Please note that this task requires a filter file which has been generated
by niprefilter2 version 2.0 or higher. It is possible to run nicerl2 to
generate a revised filter file without disturbing your event file by
running nicerl2 with the option tasks=MKF.
The task assumes you have access to NICER's Calibration Database (CALDB)
in order to access various background calibration files. The NICER CALDB can be
installed on a locally mounted disk, or accessed at the HEASARC over the internet.
Outputs
The outputs of the task is an output background pha file that can be loaded
as a background file within XSPEC. This is a standard OGIP "type I" spectrum file.
Using the Space Weather Background Spectrum in XSPEC
When run to completion, niswbkgspect produces an output pha file as specified by the
outfile parameter. You can use this file as a background file in XSPEC using the
XSPEC background command in the standard way:
data 1:1 myfile.pha
back 1 myfile-bkg.pha
resp 1:1 myfile.rmf
arf 1:1 myfile.arf
(assuming the target spectrum is myfile.pha, with an associated RMF file and associated ARF file,
and the output spectrum is myfile-bkg.pha).
PARAMETERS
- infile [filename]
- Input spectrum file name for which the background model is
to be estimated. If updatepha=YES, this file must be writable.
- outfile [filename]
- Name of output estimated background file.
- mkfile [filename]
- Name of the filter file (.mkf file).
- selfile [filename]
- Name of the file containing FPM Selection information. This should
either be the cleaned event list (recommended), although the filter
file can also be specified if necessary, with the limitations
described above.
- (gtifile="$INFILE[GTI]") [string]
- File name[extension] containing the Good Time Interval
used to create the input spectrum file. The patterns
$INFILE and $OUTFILE are replaced by the infile and outfile
parameters. Therefore, the default setting of "$INFILE[GTI]"
will look for the GTI extension of the input file.
- (auxilfile = NICER_AUXIL/30nov18targskc_enhanced.evt) [string]
- Name of background event file.
- (gti_min = 0).
- Minimum gti duration to use, in seconds.
- (selcol = INDEF) [string]
-
FPM Selection column name (or INDEF)
- (updatepha="YES") [boolean]
- If yes, then modify the input file's BACKFILE keyword to
be background file output by this task.
- (cleanup="YES") [boolean]
- If yes, then clean up temporary files. If no, temporary files
remain. This is typically for debugging.
- (clobber = NO) [boolean]
-
If the output file already exists, then setting "clobber = yes" will cause it to be overwritten.
- (chatter = 2) [integer, 0 - 5]
-
Controls the amount of informative text written to standard output.
Setting chatter = 4 or higher will produce detailed diagnostic output;
chatter = 1 prints out a basic diagnostic message. The default is to
produce a brief summary on output.
- (history = YES) [boolean]
-
If history = YES, then a set of HISTORY keywords will be written to
the header of the specified HDU in the output file to record the value
of all the niswbkgspect task parameters that were used to produce the output
file.
EXAMPLES
Run niswbkgspect for myspectrum.pha, using the spectrum's GTI, for all
pre-launch operating detectors. The filter file is ni1234567890.mkf and
the cleaned event file with FPM Selection information is in
ni1234567890_0mpu7_cl.evt.
niswbkgspect myspectrum.pha myspectrum-bkg.pha \
ni1234567890.mkf ni1234567890_0mpu7_cl.evt \
myspectrum_sky.arf myspectrm.rmf
Note that the output is stored in myspectrum-bkg.pha.
SEE ALSO
niscorpeon
nibackgen3C50
niprefilter
niprefilter2
nicerarf
nicerrmf
nicerl2
LAST MODIFIED
Sep 2022