Modelling SNR G1.9+0.3 as a supernova inside a planetary nebula

Using 3D numerical hydrodynamical simulations we show that a Type Ia supernova (SN Ia) explosion inside a planetary nebula (PN) can explain the observed shape of the G1.9+0.3 supernova remnant (SNR) and its X-ray morphology. The SNR G1.9+0.3 morphology can be generally described as a sphere with two small and incomplete lobes protruding on opposite sides of the SNR, termed 'ears', a structure resembling many elliptical PNe. Observations show the synchrotron X-ray emission to be much stronger inside the two ears than in the rest of the SNR. We numerically show that a spherical SN Ia explosion into a circumstellar matter (CSM) with the structure of an elliptical PN with ears and clumps embedded in the ears can explain the X-ray properties of SNR G1.9+0.3. While the ejecta has already collided with the PN shell in most of the SNR and its forward shock has been slowed down, the ejecta is still advancing inside the ears. The fast forward shock inside the ears explains the stronger X-ray emission there. SN Ia inside PNe (SNIPs) seem to comprise a non-negligible fraction of resolved SN Ia remnants.