2025ApJ...992..204T

We present on results of a spatially resolved spectral analysis of G1.9+0.3, the youngest known supernova remnant in the Galaxy. The X-ray spectra are well described by synchrotron emission from a power-law electron distribution with an exponential cutoff. We found a cutoff energy ϵ₀ ∼ 1 keV in both the radio bright rim and the X-ray bright rims. In the loss-limited case, the cutoff energy depends on the shock velocity v_sh and the Bohm factor η, following the relation ${\epsilon }_{0}\propto {v}_{{\rm{sh}}}^{2}{\eta }^{-1}$. Our analysis shows that η ranges from 2 to 4 in the radio rim and from 12 to 15 in the X-ray rims. This suggests that the magnetic field in the radio rim is more turbulent than in the X-ray rims. The presence of CO clouds along the radio rim likely contributes to this difference. Interaction between the shock and these clouds can slow the shock down and generate turbulent eddies. The resulting turbulence eddies can amplify the magnetic field. We propose that the strong radio emission from the radio rim is primarily due to this amplified magnetic field. In contrast, a CO cloud located in the southwest appears to lie in the foreground, as indicated by its low turbulence and the absence of shock deceleration.