Detection of a fast ejecta fragment in the atomic cloud interacting with the southwestern limb of SN 1006

Supernova remnants interacting with molecular/atomic clouds are interesting X-ray sources to study nonthermal emission. X-ray emission in these systems can be produced by different processes, e.g. low energy cosmic rays interacting with the cloud and fast ejecta fragments moving in the cloud. SN1006 is a Type Ia supernova remnant that presents an X-ray nonthermal bilateral emission, in its northeastern and southwestern limbs. Despite evolving in a fairly uniform environment, SN1006 shows two regions of interaction with atomic clouds, (northwest and southwest).We performed a combined image-spectral analysis of the X-ray emission in the interaction region between the southwestern limb of SN1006 and the cloud with NuSTAR, Chandra and XMM-Newton. We discovered an extended X-ray source approximately 2 pc upstream of the shock front. The source is characterized by a hard continuum and by Ne, Si and Fe emission lines. The observed flux suggests that the origin of the X-ray emission is not associated with low energy cosmic rays interacting with the cloud. On the other hand, the spectral properties of the source, together with the detection of an IR counterpart visible with Spitzer-MIPS at 24 μm are in agreement with expectations for a fast ejecta fragment moving within the atomic cloud.