Looking out for the Little Guys: Measuring M-Dwarf Multiplicity with High-Resolution Imaging

The M dwarfs comprise over 70% of the stars in our galaxy, and have been established as the most favorable targets for exoplanet detection and characterization using current instrumentation. However, unresolved stellar companions can contaminate the light curves of transiting planets, resulting in underestimated planet radii, skewed planet radius distributions and occurrence rates, incorrect characterization of both stars’ properties, and a bias against detecting Earth-sized planets with transit surveys such as TESS. We therefore followed up 58 M-dwarf TESS Objects of Interest using speckle imagers around the world, and found that the orbital period distribution of stellar companions to planet-hosting M dwarfs is shifted to longer periods compared to the expected distribution for field M dwarfs. Additionally, in order to obtain a control sample of M dwarfs not seen to show a transit event, we carried out the POKEMON speckle survey of nearby M dwarfs. POKEMON is volume-limited through M9 out to 15 pc, with additional brighter targets to 25 pc. In total, we obtained multiplicity measurements for 1070 nearby M dwarfs, and revealed 27 new stellar companions, resulting in an 8% increase in known stellar companions to the stars in our sample. Finally, we present the Quad-camera Wavefront-sensing Six-channel Speckle Interferometer, a next-generation speckle imager we designed and constructed for the 4.3-m Lowell Discovery Telescope that allows us to better detect and characterize low-mass pairs.