Robo-AO Kepler Planetary Candidate Survey. II. Adaptive Optics Imaging of 969 Kepler Exoplanet Candidate Host Stars

Creators: Baranec, Christoph; Ziegler, Carl; Law, Nicholas M.; Morton, Tim; Riddle, Reed; Atkinson, Dani; Schonhut, Jessica; Crepp, Justin

Abstract

We initiated the Robo-AO Kepler Planetary Candidate Survey in 2012 to observe each Kepler exoplanet candidate host star with high angular resolution, visible light, laser adaptive optics (AOs) imaging. Our goal is to find nearby stars lying in Kepler's photometric apertures that are responsible for the relatively high probability of false-positive exoplanet detections and that cause underestimates of the size of transit radii. Our comprehensive survey will also shed light on the effects of stellar multiplicity on exoplanet properties and will identify rare exoplanetary architectures. In this second part of our ongoing survey, we observed an additional 969 Kepler planet candidate hosts and we report blended stellar companions up to Δm≈6 that contribute to Kepler's measured light curves. We found 203 companions within ~4'' of 181 of the Kepler stars, of which 141 are new discoveries. We measure the nearby star probability for this sample of Kepler planet candidate host stars to be 10.6% ± 1.1% at angular separations up to 2."5, significantly higher than the 7.4% ± 1.0% probability discovered in our initial sample of 715 stars; we find the probability increases to 17.6% ± 1.5% out to a separation of 4."0. The median position of Kepler Objects of Interest (KOIs) observed in this survey are 1.°1 closer to the galactic plane, which may account for some of the nearby star probability enhancement. We additionally detail 50 Keck AO images of Robo-AO observed KOIs in order to confirm 37 companions detected at a <5σ significance level and to obtain additional infrared photometry on higher significance detected companions.

Additional Information

© 2016 The American Astronomical Society. Received 2016 March 6; accepted 2016 April 21; published 2016 June 23. This research is supported by the NASA Exoplanets Research Program, grant #NNX 15AC91G. C.B. acknowledges support from the Alfred P. Sloan Foundation. T.M. is supported by NASA grant #NNX 14AE11G under the Kepler Participating Scientist Program. D.A. is supported by a NASA Space Technology Research Fellowship, grant #NNX 13AL75H. The Robo-AO system was developed by collaborating partner institutions, the California Institute of Technology and the Inter-University Centre for Astronomy and Astrophysics, and with the support of the National Science Foundation under grant Nos. AST-0906060, AST-0960343, and AST-1207891, the Mt. Cuba Astronomical Foundation, and by a gift from Samuel Oschin. We are grateful to the Palomar Observatory staff for their support of Robo-AO on the 1.5 m telescope, particularly S. Kunsman, M. Doyle, J. Henning, R. Walters, G. Van Idsinga, B. Baker, K. Dunscombe, and D. Roderick. We thank Adam Kraus et al. for sharing a preprint of their paper. This work used the astronomy and astrophysics package for Matlab (Ofek 2014). Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: PO:1.5m (Robo-AO), Keck:II (NIRC2-LGS).

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