uvotshiftpha - shift a UVOT PHA in time assuming a power-law decay
In order to construct spectral energy distributions for use in
xspec the .pha files for each UVOT filter must be adjusted to a common
time. This routine adjusts the source count rate in a .pha file from
"intime" to "outtime". It assumes that the count
rate from the source is changing as a power law
f(t) = f(t0)*(t/t0)^alpha.
The count rate from the source is shifted to "outime" while
the background count rate remains the same. "Intime" and
"outtime" are specified in arbitrary units, but both times
must be in the same units. The times are relative to some arbitrary
The routine works for .pha files with count rates and .pha files
with total counts.
Be aware that this routine assumes a particular form for the
light curve (i.e., a power law) and will produce invalid results if
the light curve does not behave in this way.
- infile [filename]
- Input .pha file for some UVOT lenticular filter.
- intime [real]
- Time since BAT trigger of input file.
- outfile [filename]
- Output .pha file.
- outtime [real]
- Time since BAT trigger to shift to.
- alpha [real]
- Power-law index alpha for the formula f(t) = f(t0)*(t/t0)^alpha
- (cleanup = yes) [boolean]
- Remove intermediate files?
- (history = yes) [boolean]
- Write history keywords?
- (clobber = no) [boolean]
- Overwrite existing files?
- (chatter = 1) [enumerated integer]
- Standard HEAdas chatter parameter.
The following examples illustrate running uvotshiftpha
1. Run uvotshiftpha to shift the PHA from 1234 s after the BAT trigger
to 2345 s after the bat trigger assuming a power law light curve
with a slope of -1.
uvotshiftpha infile=v.pha intime=1234 outfile=vshift.pha outtime=2345 alpha=-1.