A Dearth of Stellar Companions to M-dwarf TESS Objects of Interest

The Transiting Exoplanet Survey Satellite (TESS) has proven to be a powerful resource for uncovering planets, and the M-dwarfs have been established as favorable planet hosts. It has also become apparent that stellar multiplicity has wide-ranging implications for exoplanet detection and characterization, and that speckle imaging is one of the most efficient tools for probing these multi-star systems. We therefore present high-resolution imaging observations of 63 M-dwarf TOIs using speckle imagers at the 3.5m WIYN telescope, the 4.3m Lowell Discovery Telescope (LDT), and the twin 8.1m Gemini North and South telescopes. However, only one companion was detected. This finding is in contrast to the established 46% binarity rate in exoplanet host stars and the established 27% stellar multiplicity rate for field M-dwarfs. These results indicate that M-dwarf TOIs have a much lower multiplicity rate than field M-dwarfs. Our observations also imply that planet signals detected from M-dwarf TOIs are more likely to be real than those from higher-mass stars. Finally, these data support the observation that exoplanet-hosting binary stars have, in general, wider separations than field binaries.