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Studying exoplanet host stars is of the utmost importance to establish thelink between the presence of exoplanets around various types of stars and tounderstand the respective evolution of stars and exoplanets.  Using the limb-darkened diameter (LDD) obtained from interferometric data, wedetermine the fundamental parameters of four exoplanet host stars. We areparticularly interested in the F4 main-sequence star, {\theta} Cyg, for whichKepler has recently revealed solar-like oscillations that are unexpected forthis type of star. Furthermore, recent photometric and spectroscopicmeasurements with SOPHIE and ELODIE (OHP) show evidence of a quasi-periodicradial velocity of \sim150 days. Models of this periodic change in radialvelocity predict either a complex planetary system orbiting the star, or a newand unidentified stellar pulsation mode.  We performed interferometric observations of {\theta} Cyg, 14 Andromedae,{\upsilon} Andromedae and 42 Draconis for two years with VEGA/CHARA (MountWilson, California) in several three-telescope configurations. We measuredaccurate limb darkened diameters and derived their radius, mass and temperatureusing empirical laws.  We obtain new accurate fundamental parameters for stars 14 And, {\upsilon}And and 42 Dra. We also obtained limb darkened diameters with a minimumprecision of \sim 1.3%, leading to minimum planet masses of Msini=5.33\pm 0.57,0.62 \pm 0.09 and 3.79\pm0.29 MJup for 14 And b, {\upsilon} And b and 42 Dra b,respectively. The interferometric measurements of {\theta} Cyg show asignificant diameter variability that remains unexplained up to now. We proposethat the presence of these discrepancies in the interferometric data is causedby either an intrinsic variation of the star or an unknown close companionorbiting around it.

A new interferometric study of four exoplanet host stars : {\theta} Cygni, 14 Andromedae, {\upsilon} Andromedae and 42 Draconis