uvotshiftpha - shift a UVOT PHA in time assuming a power-law decay


uvotshiftpha infile=<filename> intime=<float> outfile=<filename> outtime=<float> alpha=<float>


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 reference time.

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.


uvot2pha, xspec


February 2007