Reference-star differential imaging on SPHERE/IRDIS

Reference-star differential imaging (RDI) is a promising technique in high-contrast that thought to be more sensitive exoplanets and disks than angular (ADI) at short separations (i.e., <0.3"). However, it unknown whether the performance of RDI on ground-based instruments can improved by using all archival data optimize subtraction stellar contributions. We characterize SPHERE/IRDIS direct disks. made use H23 obtained past five years build master reference library perform RDI. In point-source detection, outperform ADI small (<0.4") if observing conditions are around median our library. On average, has gain ~0.8 mag over 0.15" separation for observations under conditions. demonstrate including targets indeed help improve disk imaging, reveal features provide robust recovery morphology. resolve 33 total intensity (19 planet-forming 14 debris disks), 4 them only detected with Two resolved scattered light first time. Three The we built this work easily implemented into legacy or future SPHERE surveys RDI, achieving better ADI. To obtain optimal gains ADI, recommend carried out seeing 0.6"-0.8".