specutils.analysis.equivalent_width(spectrum, continuum=1, regions=None)[source]

Computes the equivalent width of a region of the spectrum.

Applies to the whole spectrum by default, but can be limited to a specific feature (like a spectral line) if a region is given.

spectrum : Spectrum1D

The spectrum object overwhich the equivalent width will be calculated.

regions: `~specutils.SpectralRegion` or list of `~specutils.SpectralRegion`

Region within the spectrum to calculate the gaussian sigma width. If regions is None, computation is performed over entire spectrum.

continuum : 1 or Quantity, optional

Value to assume is the continuum level. For the special value 1 (without units), 1 in whatever the units of the spectrum.flux will be assumed, otherwise units are required and must be the same as the spectrum.flux.

ew : Quantity

Equivalent width calculation, in the same units as the spectrum’s spectral_axis.


To do a standard equivalent width measurement, the spectrum should be continuum-normalized to whatever continuum is before this function is called.