Notes on emission from SNR

Disentangling hadronic from leptonic emission in G326.3−1.8

https://www.aanda.org/articles/aa/pdf/2018/09/aa33008-18.pdf
Assuming the sedov phase, we can derive the kinetic energy released by the supernova.
It is depended on the gas density.
Can the density be determined by observations.
We describe the electron population as a broken power-law spectrum with an exponential cutoff.
The break is assumed to be due to cooling, therefore we set $\Gamma_2=\Gamma_1+1$, while the cutoff defines the maximum attainable energy if the particles.
We report the range of permitted values of free parameters, such as the total energy and electron-proton ratio $K_{ep}$.
Since the maximum energy of protons is always higher than that of electrons, which suffer synchrotron losses and other losses, we used the maximum value of maximum electron energy as a lower limit.
For the source discussed in the paper, the leptonic model requires too much energy and results in the $K_{ep}$ too large.
From the derived relation between $\tau_{syn},t_{acc},B,u_{sh}$ et al., we can derive the break energy $E_b(\tau_{syn}=t_{age})$ (???) and maximum energy E_{max}(t_{acc}=min(\tau_{syn},t_{age})).

https://www.aanda.org/articles/aa/pdf/2019/03/aa33985-18.pdf


Non-thermal emission from the reverse shock of the youngest galactic Supernova remnant G1.9+0.3
 thermal-leakage injection model.
thermal leakage can not be the only injection mechanism for electrons. The shock thickness is commensurate with the gyro radius of the incoming protons, and only particles with Larmor radii a few times that see the shock as a discontinuity and can be accelerated by DSA. For typical SNR shock speeds, electrons would only get injected into the DSA process if their momentum is above a few tens of MeV/c.

However, a fraction of the electrons might be pre-accelerated at the shock, for instance by shock-surfing acceleration or shock drift acceleration.

we consider two realizations of the diffusion coefficient. The first option is to assume Bohm diffusion close to the shock and in the downstream region, and to have a transition to the galactic diffusion coefficient further upstream.


 Alternatively the amplification of Alfvenic turbulence can be explicitely treated by solving a sep- ´ arate wave transport equation and thus calculating the diffusion coefficient self-consistently (Brose et al. 2016).

Here we assumed Bohm-like diffusion in the downstream and in the upstream of the remnant up to a radius of 1.1 · Rsh. From 2 · Rsh we used the galactic diffusion coefficient, and an exponential profile connects the two regimes in the intermediate range.

Usually, just a few per cent of the thermal energy of the plasma are assumed to be transformed to magnetic-field energy - otherwise the evolution of SNRs should considerably deviate from purely hydrodynamical predictions.

The strong synchrotron cooling also has effects on the morphology of the remnant. In the emission profiles, the X-ray peak is always close behind the forward shock, as only recently accelerated electrons have sufficient energy to emit X-ray photons. Radio photons, on the other hand, can be emitted by all previously accelerated electrons in the downstream

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https://www.aanda.org/articles/aa/pdf/2009/37/aa11948-09.pdf