  The Transiting Exoplanet Survey Satellite (TESS) is conducting a two-year
wide-field survey searching for transiting exoplanets around nearby bright
stars that will be ideal for follow-up characterization. To facilitate studies
of planet compositions and atmospheric properties, accurate and precise
planetary radii need to be derived from the transit light curves. Since 40 -
50% of exoplanet host stars are in multiple star systems, however, the observed
transit depth may be diluted by the flux of a companion star, causing the
radius of the planet to be underestimated. High angular resolution imaging can
detect companion stars that are not resolved in the TESS Input Catalog, or by
seeing-limited photometry, to validate exoplanet candidates and derive accurate
planetary radii. We examine the population of stellar companions that will be
detectable around TESS planet candidate host stars, and those that will remain
undetected, by applying the detection limits of speckle imaging to the
simulated host star populations of Sullivan et al. (2015) and Barclay et al.
(2018). By detecting companions with contrasts of delta m < 7 - 9 and
separations of ~0.02 - 1.2'', speckle imaging can detect companion stars as
faint as early M stars around A - F stars and stars as faint as mid-M around G
- M stars, as well as up to 99% of the expected binary star distribution for
systems located within a few hundred parsecs.
