make it possible to initialize XraySpectrum1D without inputs

Author: eblur

specutils/spectra/xrayspectrum1d.py

@@ -75,14 +75,19 @@ class XraySpectrum1D(Spectrum1D):
 
     rmf
     """
-    def __init__(self, bin_lo, bin_hi, bin_unit, counts, exposure,
-                 arf=None, rmf=None, rest_value=0.0 * u.angstrom, **kwargs):
+    def __init__(self, bin_lo=None, bin_hi=None, bin_unit=None,
+                 counts=None, exposure=1.0, arf=None, rmf=None,
+                 rest_value=0.0 * u.angstrom, **kwargs):
         try:
             axis_unit = u.Unit(bin_unit)
         except ValueError:
             axis_unit = _unit_parser(bin_unit)
 
-        bin_mid = 0.5 * (bin_lo + bin_hi) * axis_unit
+        if (bin_lo is not None) and (bin_hi is not None):
+            bin_mid = 0.5 * (bin_lo + bin_hi) * axis_unit
+        else:
+            bin_mid = None
+        
         Spectrum1D.__init__(self, spectral_axis=bin_mid, flux=counts,
                             rest_value=rest_value, **kwargs)
 

specutils/tests/test_xrayspectrum1d.py

@@ -3,6 +3,10 @@
 from astropy.modeling.powerlaws import PowerLaw1D
 from specutils import XraySpectrum1D
 
+def test_init_spectrum():
+    test = XraySpectrum1D()
+    return
+
 def test_create_from_arrays():
     # Test that XraySpectrum1D can be initialized
     amp0, alpha0 = 3.e-3, 2.0