CrabSpectrum

class gammapy.spectrum.CrabSpectrum(reference='meyer')

Bases: object

Crab spectral model.

The following references are available:

• ‘meyer’, 2010arXiv1008.4524M
• ‘hegra’, 2004ApJ...614..897A
• ‘hess_pl’, 2006A&A...457..899A
• ‘hess_ecpl’, 2006A&A...457..899A

Parameters:

reference : {‘meyer’, ‘hegra’, ‘hess_pl’, ‘hess_ecpl’}

Which reference to use for the spectral model.

Examples

Plot the ‘hess_ecpl’ reference crab spectrum between 1 TeV and 100 TeV:

>>> from gammapy.spectrum import CrabSpectrum
>>> import astropy.units as u
>>> crab_hess_ecpl = CrabSpectrum('hess_ecpl')
>>> crab_hess_ecpl.model.plot([1, 100] * u.TeV)

Use a reference crab spectrum as unit to measure flux:

>>> from astropy import units as u
>>> from gammapy.spectrum import CrabSpectrum
>>> from gammapy.spectrum.models import PowerLaw
>>>
>>> # define power law model
>>> amplitude = 1e-12 * u.Unit('1 / (cm2 s TeV)')
>>> index = 2.3
>>> reference = 1 * u.TeV
>>> pwl = PowerLaw(index, amplitude, reference)
>>>
>>> # define crab reference
>>> crab = CrabSpectrum('hess_pl').model
>>>
>>> # compute flux at 10 TeV in crab units
>>> energy = 10 * u.TeV
>>> flux_cu = (pwl(energy) / crab(energy)).to('%')
>>> print(flux_cu)
6.19699156377 %

And the same for integral fluxes:

>>> # compute integral flux in crab units
>>> emin, emax = [1, 10] * u.TeV
>>> flux_int_cu = (pwl.integral(emin, emax) / crab.integral(emin, emax)).to('%')
>>> print(flux_int_cu)
3.5350582166 %