Three new late-type stellar companions to very dusty WISE debris disks identified with VLT/SPHERE imaging

TL;DR

This study used VLT/SPHERE imaging to discover three new stellar companions to debris disk stars, providing insights into the relationship between stellar companions, dust, and potential planetary systems.

Contribution

First high contrast imaging survey targeting debris disk stars with high dust levels, discovering three new stellar companions and characterizing their properties.

Findings

Identified three new stellar companions around debris disk stars.

Detected additional wide-separation stellar companions in Gaia catalog.

Survey sensitivity reached 10.4Mj at 25au and 5.9Mj at 100au.

Abstract

Debris disk stars are good targets for high contrast imaging searches for planetary systems, since debris disks have been shown to have a tentative correlation with giant planets. We selected 20 stars identified as debris disk hosts by the WSIE mission, with particularly high levels of warm dust. We observed these with the VLT/SPHERE high contrast imaging instrument with the goal of finding planets and imaging the disks in scattered light. Our survey reaches a median 5$\sigma$~sensitivity of 10.4Mj at 25au and 5.9Mj at 100au. We identified three new stellar companions (HD18378B, HD19257B and HD133778B): two are mid-M type stars and one is late-K or early-M star. Three additional stars have very widely separated stellar companions (all at $>$2000au) identified in the Gaia catalog. The stars hosting the three SPHERE-identified companions are all older ($\gtrsim$700Myr), with one having recently left the main sequence and one a giant star. We infer that the high volumes of dust observed around these stars might have been caused by a recent collision between the planets and planetesimal belts in the system, although for the most evolved star, mass loss could also be responsible for the infrared excess. Future mid-IR spectroscopy or polarimetric imaging may allow the positions and spatial extent of these dust belts to be constrained, thereby providing evidence as to the true cause of the elevated levels of dust around these old systems. None of the disks in this survey are resolved in scattered light.