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Bugs: dmgti
A list of
bugs fixed in CIAO 3.4
is available.
Bugs
When using status bits in an expression, only the last
condition is checked.
Intersecting a new GTI with an existing file does not
work.
(01 Dec 2006)
Bugs
-
When using status bits in an expression, only the last
condition is checked.
When using status bits in an expression such
"status==X1F,X3T,X18F", only the last condition
(here, "X18F") is checked.
Workaround:
Set the logic explicitly:
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logical "AND": status=((bits==X1T)&&(bits==X2T))
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logical "OR": status=((bits==X1T)||(bits==X2T))
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Intersecting a new GTI with an existing file does not
work.
(01 Dec 2006)
If the name of an existing GTI file is given as the outfile parameter of another
dmgti run, the tool is supposed to modify it in
place to intersect the new GTI with the old GTIs. This bug
results in the output file containing only the GTI for the
last userlimit condition.
Workaround:
Run dmgti multiple times to create separate GTI
files, then use dmcopy to apply the
GTI filters to the data.
The following is a list of bugs that were fixed
in the CIAO 3.4
software release.
-
Use of time information by dmgti causes filter to appear
shifted (generally seen for lightcurves)
dmgti uses the TIMEPIXR and TIMEDEL keywords to modify the
TIME column when creating GTI files. TIMEPIXR defines
whether or not the TIME column should be taken to mean the
beginning (TIMEPIXR=0), the middle (TIMEPIXR=0.5) or end
(TIMEPIXR=1) of the bin. TIMEDEL records the time
resolution of the data; this is the bin size between rows
for a binned dataset or the resolution of the time stamp
for event lists. Refer to "ahelp chandra times" for
further details on the time information in Chandra data.
The way that dmgti uses the time information may
result in a filter that appears shifted from the expected
times for files where TIMEPIXR is not equal to 0. This is
generally seen when creating filters for lightcurves.
Workaround:
To get the desired filter when working with lightcurves,
rename the TIME_MIN column in the lightcurve input to
dmgti to TIME. This means that the GTI filter will
actually be determined using the TIME_MIN values.
Assume that the original lightcurve created by
dmextract is called "lc.fits". This
dmcopy command
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copies the TIME column to TIME_ORIG
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copies the TIME_MIN column to TIME
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copies the rest of the columns ("*") to the output file
as-is
unix% dmcopy "lc.fits[cols TIME_ORIG=TIME,TIME=TIME_MIN,*]" lc_cols_new.fits
Then use the new file in the dmgti
command, e.g.
unix% dmgti lc_cols_new.fits lc_rate_0.06.gti userlimit="count_rate<0.06"
For more information on working with lightcurves, refer to
the CIAO Timing
Threads.
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The tool does not check that the input virtual file syntax
is valid.
(13 Jun 2006)
It will segmentation fault if the input filter uses a column
name that does not exist in the file.
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