Looking out for the Little Guys: Measuring M-dwarf Multiplicity with Speckle 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 present POKEMON (Pervasive Overview of Kompanions of Every M-dwarf in Our Neighborhood), the largest speckle survey of M-dwarf multiplicity produced to-date. POKEMON is a volume-limited survey through M9 that inspected, at diffraction-limited resolution, every M-dwarf out to 15pc, with additional brighter targets to 25pc. In total, we observed 1151 nearby M-dwarfs, and revealed 38 new stellar companions, resulting in a ~9% increase in known stellar companions to the stars in our sample. We also report results from our speckle follow-up of 58 M-dwarf TESS Objects of Interest. These observations suggest 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. 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.