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We present high angular resolution imaging observations of 517 host stars ofTESS exoplanet candidates using the `Alopeke and Zorro speckle cameras atGemini North and South. The sample consists mainly of bright F, G, K stars atdistances of less than 500 pc. Our speckle observations span angularresolutions of ~20 mas out to 1.2 arcsec, yielding spatial resolutions of <10to 500 AU for most stars, and our contrast limits can detect companion stars5-9 magnitudes fainter than the primary at optical wavelengths. We detect 102close stellar companions and determine the separation, magnitude difference,mass ratio, and estimated orbital period for each system. Our observations ofexoplanet host star binaries reveal that they have wider separations than fieldbinaries, with a mean orbital semi-major axis near 100 AU. Other imagingstudies have suggested this dearth of very closely separated binaries insystems which host exoplanets, but incompleteness at small separations makes itdifficult to disentangle unobserved companions from a true lack of companions.With our improved angular resolution and sensitivity, we confirm that this lackof close exoplanet host binaries is indeed real. We also search for acorrelation between planetary orbital radii vs. binary star separation, butgiven the very short orbital periods of the TESS planets, we do not find anyclear trend. We do note that in exoplanet systems containing binary host stars,there is an observational bias against detecting Earth-size planet transits dueto transit depth dilution caused by the companion star.

Speckle Observations of TESS Exoplanet Host Stars. II. Stellar Companions at 1-1000 AU and Implications for Small Planet Detection