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Description
The interaction between low-mass companions and the debris disks they reside in is still not fully understood. A debris disk can evolve due to self-stirring, a process in which planetesimals can excite their neighbours to the point of destructive collisions. On top of this, the presence of a companion could further stir the disk (companion-stirring). Additional information is necessary to understand this fundamental step in the formation and evolution of a planetary system, and at the moment of writing only a handful of systems are known in which both a companion and a debris disk have been detected and studied at the same time. Our primary goal is to augment the sample of such systems and understand the relative importance between self-stirring and companion-stirring. In the course of the VLT/NaCo-ISPY Imaging Survey for Planets around Young stars, we observed HD 193571, an A0 debris disk hosting star at a distance of 68 pc with an age between 60-170Myr. We obtained two sets of observations in L' band and a third epoch in H band using the GPI instrument at Gemini-South. A companion was detected in all three epochs at a projected separation of 11au (0.17-arcsec), and co-motion was confirmed through proper motion analysis. Given the inferred disk size of 120au, the companion appears to reside within the gap between the host star and the disk. Comparison between the L' and H band magnitude and evolutionary tracks suggests a mass of 0.31-0.39M_{sun}_. We discovered a previously unknown M-dwarf companion around HD 193571, making it the third low-mass stellar object discovered within a debris disk. Comparison to self- and companion-stirring models suggests that the companion is likely responsible for the stirring of the disk.
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