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| -rw-r--r-- | README.md | 1 | ||||
| -rw-r--r-- | scripts/acis.py | 34 | ||||
| -rw-r--r-- | scripts/spectrum.py | 44 |
3 files changed, 79 insertions, 0 deletions
@@ -85,6 +85,7 @@ Installation * [ruamel.yaml](https://bitbucket.org/ruamel/yaml) * [numpy](http://numpy.org/) * [scipy](https://scipy.org/) + * [astropy](http://www.astropy.org/) Settings diff --git a/scripts/acis.py b/scripts/acis.py new file mode 100644 index 0000000..5200f4e --- /dev/null +++ b/scripts/acis.py @@ -0,0 +1,34 @@ +# Copyright (c) 2017 Weitian LI <liweitianux@live.com> +# MIT license + +""" +Chandra ACIS utilities +""" + +import math + + +class ACIS: + """ + Chandra ACIS detector properties and utilities. + + References + ---------- + [1] CIAO - dictionary - ACIS (advanced camera for imaging and spectroscopy) + http://cxc.harvard.edu/ciao/dictionary/acis.html + [2] CIAO - Dictionary - PI (pulse invariant) + http://cxc.harvard.edu/ciao/dictionary/pi.html + """ + # Pixel size + pixel2arcsec = 0.492 # [arcsec] + # Number of channels + nchannel = 1024 + # Channel energy width + echannel = 14.6 # [eV] + + @classmethod + def energy2channel(self, energy): + """ + Convert energy [eV] to channel number. + """ + return math.floor(energy/self.echannel + 1) diff --git a/scripts/spectrum.py b/scripts/spectrum.py new file mode 100644 index 0000000..ad38b0d --- /dev/null +++ b/scripts/spectrum.py @@ -0,0 +1,44 @@ +# Copyright (c) 2017 Weitian LI <liweitianux@live.com> +# MIT license + +""" +Chandra ACIS spectrum. +""" + + +from astropy.io import fits + +from acis import ACIS + + +class Spectrum: + """ + Chandra ACIS spectrum + """ + def __init__(self, filepath): + self.filepath = filepath + self.fitsobj = fits.open(filepath) + ext_spec = self.fitsobj["SPECTRUM"] + self.header = ext_spec.header + # spectral data + self.channel = ext_spec.data.columns["CHANNEL"].array + self.counts = ext_spec.data.columns["COUNTS"].array + # spectral keywords + self.EXPOSURE = self.header.get("EXPOSURE") + self.BACKSCAL = self.header.get("BACKSCAL") + + def calc_pb_flux(self, elow=9500, ehigh=12000): + """ + Calculate the particle background flux: + flux = counts / exposure / area + + Parameters + ---------- + elow, ehigh : float, optional + Lower and upper energy limit for the particle background. + """ + chlow = ACIS.energy2channel(elow) + chhigh = ACIS.energy2channel(ehigh) + counts = self.counts[(chlow-1):chhigh].sum() + flux = counts / self.EXPOSURE / self.BACKSCAL + return flux |