Auxiliary Response File (ARF)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The Auxiliary Response File (frequenty referred to simply as **ARF**)
defines the telescope efficiency as a function of energy. This is
typically a 1D file with units of [cm^2 counts / photon] as a function
of photon energy. See the `CXC documentation page on ARFs
<https://cxc.cfa.harvard.edu/ciao/dictionary/arf.html>`_

.. autoclass:: pyxsis.xrayspectrum1d.ARF
    :members: