WASP-12b AND HAT-P-8b ARE MEMBERS OF TRIPLE STAR SYSTEMS

Abstract

We present high spatial resolution images that demonstrate the hot Jupiters\nWASP-12b and HAT-P-8b orbit the primary star of hierarchical triple star\nsystems. In each case, two distant companions with colors and brightness\nconsistent with M dwarfs co-orbit the planet host as well as one another. Our\nadaptive optics images spatially resolve the secondary around WASP-12,\npreviously identified by Bergfors et al. 2011 and Crossfield et al. 2012, into\ntwo distinct sources separated by 84.3+/-0.6 mas (21 +/- 3 AU). We find that\nthe secondary to HAT-P-8, also identified by Bergfors et al. 2011, is in fact\ncomposed of two stars separated by 65.3+/-0.5 mas (15+/-1 AU). Our follow-up\nobservations demonstrate physical association through common proper-motion.\nHAT-P-8 C has a particularly low mass, which we estimate to be 0.18+/-0.02Msun\nusing photometry. Due to their hierarchy, WASP-12 BC and HAT-P-8 BC will enable\nthe first dynamical mass determination for hot Jupiter stellar companions.\nThese previously well-studied planet hosts now represent higher-order\nmulti-star systems with potentially complex dynamics, underscoring the\nimportance of diffraction-limited imaging and providing additional context for\nunderstanding the migrant population of transiting hot Jupiters.\n