Follow-up Imaging of Disk Candidates from the Disk Detective Citizen Science Project: New Discoveries and False-Positives in WISE Circumstellar Disk Surveys

Abstract

The Disk Detective citizen science project aims to find new stars with excess 22-$\mu$m emission from circumstellar dust in the AllWISE data release from the Wide-field Infrared Survey Explorer (WISE). We evaluated 261 Disk Detective objects of interest with imaging with the Robo-AO adaptive optics instrument on the 1.5m telescope at Palomar Observatory and with RetroCam on the 2.5m du Pont telescope at Las Campanas Observatory to search for background objects at 0.15''-12'' separations from each target. Our analysis of these data lead us to reject 7% of targets. Combining this result with statistics from our online image classification efforts implies that at most $7.9\% \pm 0.2\%$ of AllWISE-selected infrared excesses are good disk candidates. Applying our false positive rates to other surveys, we find that the infrared excess searches of McDonald et al. (2012), McDonald et al. (2017), and Marton et al. (2016) all have false positive rates $>70\%$. Moreover, we find that all thirteen disk candidates in Theissen & West (2014) with W4 signal-to-noise >3 are false positives. We present 244 disk candidates that have survived vetting by follow-up imaging. Of these, 213 are newly-identified disk systems. Twelve of these are candidate members of comoving pairs based on \textit{Gaia} astrometry, supporting the hypothesis that warm dust is associated with binary systems. We also note the discovery of 22 $\mu$m excess around two known members of the Scorpius-Centaurus association, and identify known disk host WISEA J164540.79-310226.6 as a likely Sco-Cen member. Thirty-one of these disk candidates are closer than $\sim 125$ pc (including 27 debris disks), making them good targets for direct imaging exoplanet searches.