Source code for ixpeobssim.utils.chandra

# Copyright (C) 2016--2022 the ixpeobssim team.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

"""Utilities for the Chandra to IXPE conversion.

from __future__ import print_function, division

import os
import numpy

from import fits

from ixpeobssim.utils.logging_ import logger
from ixpeobssim import IXPEOBSSIM_IRF
from ixpeobssim.core.spline import xInterpolatedUnivariateSpline, xInterpolatedBivariateSpline

# pylint: disable=invalid-name, too-many-arguments, no-member

__BASE_IRF_FOLDER = os.path.join(IXPEOBSSIM_IRF, 'fits')

[docs] def gti(gtidata): """Return the sum of the GTI in the corresponding extension data. """ return (gtidata.field('STOP') - gtidata.field('START')).sum()
[docs] def livetime(header): """Return the livetime of the observation. """ return header['LIVETIME']
[docs] def pointing(header): """Return the pointing direction. """ try: ra = header['RA_PNT'] dec = header['DEC_PNT'] except KeyError: ra = header['RA_TARG'] dec = header['DEC_TARG'] return ra, dec
[docs] def load_arf(detname='ACIS-I'): """Load the Chandra effective area data from file. """ detname = detname.lower().replace('-', '_') assert detname in ['acis_s', 'acis_i'] file_path = os.path.join(__BASE_IRF_FOLDER, 'chandra_%s.arf' % detname)'Loading Chandra effective area from %s...', file_path) with as hdu_list: tbdata = hdu_list['SPECRESP'].data _x = 0.5*(tbdata.field('ENERG_LO') + tbdata.field('ENERG_HI')) _y = tbdata.field('SPECRESP') fmt = dict(xlabel='Energy [keV]', ylabel='Effective area [cm$^2$]') return xInterpolatedUnivariateSpline(_x, _y, **fmt)
[docs] def load_vign(): """Load the Chandra vignetting data from file. """ file_path = os.path.join(__BASE_IRF_FOLDER, 'chandra_vignet.fits')'Loading Chandra vignetting from %s...', file_path) with as hdu_list: tbdata = hdu_list['AXAF_VIGNET'].data _x = 0.5*(tbdata.field('ENERG_LO') + tbdata.field('ENERG_HI'))[0,:] _y = tbdata.field('THETA')[0,:] _vignet = tbdata.field('VIGNET') _z = numpy.mean(_vignet[0,:,:,:], axis=0) _mask = _y <= 10 #arcmin _y = _y[_mask] _z = _z[_mask, :] fmt = dict(xlabel='Energy [keV]', ylabel='Off-axis angle [arcmin]', zlabel='Vignetting') return xInterpolatedBivariateSpline(_x, _y, _z.T, **fmt)
[docs] def arf_ratio(ixpe_arf, ixpe_vign, chandra_arf, chandra_vign, emin=1., emax=10., thetamax=8.5): """Make the ratio between IXPE and Chandra effective area taking in account the vignetting. This is returning an interpolated bivariate spline in the energy-off-axis angle plane (the energy is measured in keV and the off-axis angle in arcmin). """ _x = numpy.arange(emin, emax, 0.005) _y = numpy.arange(0., thetamax, 0.05) _arf_ratio = ixpe_arf(_x) / chandra_arf(_x) _x_mesh, _y_mesh = numpy.meshgrid(_x, _y) _vign_ratio = ixpe_vign(_x_mesh, _y_mesh) / chandra_vign(_x_mesh, _y_mesh) _z = _vign_ratio * _arf_ratio fmt = dict(xlabel='Energy [keV]', ylabel='Off-axis angle [arcmin]', zlabel='Effective area ratio') return xInterpolatedBivariateSpline(_x, _y, _z.T, **fmt)