Sensitivity Tools

The fermipy-flux-sensitivity script can be used to calculate the LAT detection threshold versus energy. Inputs are the galactic diffuse model and the livetime cube of the observation epoch. The obs_time_yr option can be used to rescale the livetime cube to a shorter or longer observation time.

$ fermipy-flux-sensitivity --glon=30 --glat=30 --output=flux.fits \
--ltcube=ltcube.fits --galdiff=gll_iem_v06.fits --event_class=P8R2_SOURCE_V6

If no livetime cube is provided then the sensitivity will be computed assuming an “ideal” survey-mode operation with uniform exposure over the whole sky and no Earth obscuration or deadtime. By default the flux sensitivity will be calculated for a TS threshold of 25 and at least 3 counts.

The output FITS file contains a table with the flux threshold in each energy bin.

from astropy.table import Table
tab = Table.read('flux.fits')
print(tab['e_min'], tab['e_max'], tab['flux'])