# SNR¶

class gammapy.astro.source.SNR(e_sn='1e51 erg', theta=<Quantity 0.1>, n_ISM=<Quantity 1. 1 / cm3>, m_ejecta=<<class 'astropy.constants.iau2015.IAU2015'> name='Solar mass' value=1.9884754153381438e+30 uncertainty=9.236140093538353e+25 unit='kg' reference='IAU 2015 Resolution B 3 + CODATA 2014'>, t_stop=<Quantity 1000000. K>, age=None, morphology='Shell2D', spectral_index=2.1)[source]

Bases: object

Simple supernova remnant (SNR) evolution model.

The model is based on the Sedov-Taylor solution for strong explosions.

Parameters: e_sn : Quantity SNR energy (erg), equal to the SN energy after neutrino losses theta : Quantity Fraction of E_SN that goes into cosmic rays n_ISM : Quantity ISM density (g cm^-3) m_ejecta : Quantity Ejecta mass (g) t_stop : Quantity Post-shock temperature where gamma-ray emission stops

Attributes Summary

 sedov_taylor_begin Characteristic time scale when the Sedov-Taylor phase of the SNR’s evolution begins. sedov_taylor_end Characteristic time scale when the Sedov-Taylor phase of the SNR’s evolution ends.

Methods Summary

 luminosity_tev(self, t[, energy_min]) Gamma-ray luminosity above energy_min at age t. radius(self, t) Outer shell radius at age t. radius_inner(self, t[, fraction]) Inner radius at age t of the SNR shell.

Attributes Documentation

sedov_taylor_begin

Characteristic time scale when the Sedov-Taylor phase of the SNR’s evolution begins.

The beginning of the Sedov-Taylor phase of the SNR is defined by the condition, that the swept up mass of the surrounding medium equals the mass of the ejected mass.

The time scale is given by:

$t_{begin} \approx 200 \left(\frac{E_{SN}}{10^{51}erg}\right)^{-1/2} \left(\frac{M_{ej}}{M_{\odot}}\right)^{5/6} \left(\frac{\rho_{ISM}}{10^{-24}g/cm^3}\right)^{-1/3} \text{yr}$
sedov_taylor_end

Characteristic time scale when the Sedov-Taylor phase of the SNR’s evolution ends.

The end of the Sedov-Taylor phase of the SNR is defined by the condition, that the temperature at the shock drops below T = 10^6 K.

The time scale is given by:

$t_{end} \approx 43000 \left(\frac{m}{1.66\cdot 10^{-24}g}\right)^{5/6} \left(\frac{E_{SN}}{10^{51}erg}\right)^{1/3} \left(\frac{\rho_{ISM}}{1.66\cdot 10^{-24}g/cm^3}\right)^{-1/3} \text{yr}$

Methods Documentation

luminosity_tev(self, t, energy_min='1 TeV')[source]

Gamma-ray luminosity above energy_min at age t.

The luminosity is assumed constant in a given age interval and zero before and after. The assumed spectral index is 2.1.

The gamma-ray luminosity above 1 TeV is given by:

$L_{\gamma}(\geq 1TeV) \approx 10^{34} \theta \left(\frac{E_{SN}}{10^{51} erg}\right) \left(\frac{\rho_{ISM}}{1.66\cdot 10^{-24} g/cm^{3}} \right) \text{ s}^{-1}$

Parameters: t : Quantity Time after birth of the SNR energy_min : Quantity Lower energy limit for the luminosity
radius(self, t)[source]

Outer shell radius at age t.

The radius during the free expansion phase is given by:

$r_{SNR}(t) \approx 0.01 \left(\frac{E_{SN}}{10^{51}erg}\right)^{1/2} \left(\frac{M_{ej}}{M_{\odot}}\right)^{-1/2} t \text{ pc}$

The radius during the Sedov-Taylor phase evolves like:

$r_{SNR}(t) \approx \left(\frac{E_{SN}}{\rho_{ISM}}\right)^{1/5}t^{2/5}$
Parameters: t : Quantity Time after birth of the SNR
radius_inner(self, t, fraction=0.0914)[source]

Inner radius at age t of the SNR shell.

Parameters: t : Quantity Time after birth of the SNR