Detecting and characterizing stellar companions to exoplanet host stars

A factor that can affect the detection of exoplanets is the binarity of the host stars. Such a factor cannot be easily dismissed since the multiplicity of the stellar systems within our own Milky Way are quite common and that such systems can place further constraints on orbital dynamics and evolution. We used the Differential Speckle Survey Instrument (DSSI) at the Gemini-North Observatory to obtain AO images at 692 nm and 880 nm bands. From our survey, we detect stellar companions to the known exoplanet host stars HD 2638 and HD 164509. The stellar companion to HD 2638 has been previously detected, but the companion to HD 164509 is newly discovered. The results from observations and the stellar isochrone models are consistent with the detected companions being late-type M dwarfs. The nondetection of stellar companions to the remaining systems provides constraints on the possible presence of additional planets in those systems.