NAME
ixpepolarization -- Calculates overall Stokes parameters for a user-defined region.
USAGE
ixpepolarization.py infile regfile t_lo t_up pi_lo pi_up color scale
DESCRIPTION
ixpepolarization computes the overall Stokes parameters Q and U for a sky region defined by the user (e.g., using the display program ds9) over a user-defined time interval and a user-defined PI energy range. The program also outputs a display region file with the polarization fraction and orientation on the sky computed from the Q and U, as well as the standard error of the resulting Q and U values for the region.
The tool requires an input IXPE event FITS file (infile) and optional sky region (regfile), time interval (t_lo, t_up), and energy bounds (pi_lo, pi_up). The default is to compute the Stokes parameters from all events in the file. Clearly, as IXPE is an imaging polarimeter, only Stokes parameters for a region of the sky will be scientifically interesting.
It is therefore highly recommended that a region file be provided to ixpepolarization. From the Stokes parameters Q and U, the polarization fraction and the position angle of the polarization vector are also computed with the vector length scaled by the parameter (scale). A modified region file is output which, when displayed in ds9, includes a vector in each of the original regions denoting the polarization fraction and orientation on the sky, as well as the standard error of the resulting Q and U values for the region, along with a scale in the top right corner.
PARAMETERS
- infile* (str)
- Input FITS EVENTS file.
- regfile (str)
- Path to ASCII region definition file. (default: -)
- t_lo (str)
- ISOT date/time of lower time bound. (default: -)
- t_up (str)
- ISOT date/time of upper time bound. (default: -)
- pi_lo (str)
- Lower PI bound for event filtering. (default: -)
- pi_lo (str)
- Upper PI bound for event filtering. (default: -)
- color (str)
- Polarization vector display color. (default: red)
- scale (float)
- Polarization vector length scale factor. (default: 0.1)
- outfile (str)
- Path to output file. (default: is none)
EXAMPLES
BUGS
SEE ALSO
LAST MODIFIED
Feb 2022