From 2aaf7d8106e7d596654c9ae1cf0fa75fd642f3eb Mon Sep 17 00:00:00 2001
From: Aaron LI <aaronly.me@outlook.com>
Date: Sun, 19 Feb 2017 16:26:40 +0800
Subject: Setup module 'acispy' and clean 'scripts' directory

Setup a module 'acispy' to hold some generic Python modules for
better/easier reuse, and clean up the 'scripts' directory, which will be
used to hold the CLI tools.
---
 acispy/spectrum.py | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 acispy/spectrum.py

(limited to 'acispy/spectrum.py')

diff --git a/acispy/spectrum.py b/acispy/spectrum.py
new file mode 100644
index 0000000..ad38b0d
--- /dev/null
+++ b/acispy/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
-- 
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