Stellar Companions of Exoplanet Host Stars in K2,
Rachel Matson, NASA Postdoctoral Fellow
Binary stars are ubiquitous throughout the galaxy, with roughly half of all nearby solar-type stars having at least one companion. Stellar companions can have significant implications for the detection and characterization of exoplanets, including triggering false positives and masking the true sizes of planets. Ground-based high-resolution speckle imaging uses large numbers of short exposures to freeze out variations in atmospheric turbulence in order to detect stellar companions within one arc second of exoplanet host stars. If no companion is detected such observations set strict limits on possible companions which, if unaccounted for, can cause exoplanet radii to be underestimated. When companions are detected, speckle imaging can constrain the properties of the companion and enable the planetary radii to be corrected. To better understand the impact of stellar multiplicity on planet characteristics and detection rates, we use speckle data of K2 planet candidates to determine the companion fraction of host stars. By comparing the observed companion rate to TRILEGAL star count simulations and the detection limits of speckle imaging, we estimate the binary fraction of K2 planet host stars to be similar to that of field stars.
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