High spatial resolution imaging of the star with a transiting planet WASP-33 (Research Note)

Abstract

Context. The planetary system WASP-33 is an interesting target because of the discovery of a transiting planet, the misalignment of the stellar rotation axis and the planet orbit, the possible existence of an additional planet in the system, and the presence of δ Scuti pulsations in the hosting star. Its study promises in particular to help us understand the origin and evolution of giant planets orbiting very close to a star. Aims. We analyse high spatial resolution imaging with an adaptive optics system on the W.M. 10  m-Keck II telescope to investigate the prediction of an additional planet, and any other objects, and constrain the possible formation scenarios of the system. Methods. In November 2010, we recorded high spatial resolution images from 1 to 2.5 μm using the W.M. 10  m-Keck II telescope and its adaptive optics system, obtaining broad (Jc,Hc, and Kc) and narrow-band (FeII) images of the system. After data reduction, the contrast and angular resolution provided by this instrument allowed us to constrain the multiplicity of this system and detect one potential companion. Results. We present the discovery of a new object at a distance of 1.961′′ ± 0.003′′ from the WASP-33, at a position angle of 276.32 ± 0.24 deg. It might be either a dwarf star or brown dwarf, or an extragalactic object. In the case of a galactic object and assuming the same distance from the Sun, it would be 227 AU from the central star. We find no evidence of any additional objects. This constrains the possible constituents of the system, depending on its age and the constituent masses. Conclusions. We find a potential companion object to WASP-33. We need to confirm the gravitational link, but this object could influence the evolution of the planetary system depending on its orbital eccentricity. We exclude the existence of any additional objects. For example, objects of 0.8 M· at projected physical distances greater than [2, 5] AU, objects of 0.3 M · at projected physical distances greater than [11, 18] AU, or objects of 0.072 M· at projected physical distances greater than [18, 75] AU, depending on the age of the system. © 2011 ESO.