SeeKAT tied-array beam localiser

Likelihood estimation for the coordinates of a transient detected in multiple tied-array beams.

Download .zip Download .tar.gz

• Reads in list of detections (RA, Dec, S/N) and the beam PSF. PSFs can be modelled using MOSAIC (

• Computes a covariance matrix of the S/N value ratios, assuming 1-sigma Gaussian errors on each measurement.

• Models the aggregate beam response by arranging beam PSFs appropriately relative to each other.

• Calculates a likelihood distribution of obtaining the observed S/N in each beam according to the modelled response.

• Plots the likelihood function over RA and Dec with 1-sigma uncertainty, overlaid on the beam coordinates and sizes.

Usage: python -f {coordinates file} -p {.fits file} –r {PSF resolution} –o {fractional overlap}


python -f {coordinates file} -p {.fits file} –c {.json file} –r {PSF resolution}

Customisation options:

–n Computes the likelihood map using only the n brightest pairs of beams.

–clip All values of the CB PSF below this value are set to zero. Helps negate low-level sidelobes.

–s In the format RA(hms),Dec(dms) adds a marker for known coordinates to plot.

–scalebar Sets the length of the scalebar on the plot in arcseconds. Set to 0 to omit it altogether.

–zoom Automatically zooms in on the TABs.

–ticks Sets the spacing between axis ticks in number of pixels.

–nsig Draws uncertainty contours up to this number of standard deviations.

–fits Writes likelihood to fits file.