High-resolution Imaging of Transiting Extrasolar Planetary systems (HITEP)

II. Lucky Imaging results from 2015 and 2016^★,★★

¹ Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
e-mail: d.f.evans@keele.ac.uk
² Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen Øster Voldgade 5, 1350 Copenhagen, Denmark
³ Centre for Exoplanet Science, SUPA School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK
⁴ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
⁵ Dipartimento di Fisica “E.R. Caianiello”, Università di Salerno, via Giovanni Paolo II 132, 84084 Fisciano, Italy
⁶ Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, 80126 Napoli, Italy
⁷ Universitamburg, Faculty of Mathematics, Informatics and Natural Sciences, Department of Earth Sciences, Meteorological Institute, Bundesstra 55, 20146 Hamburg, Germany
⁸ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁹ INAF–Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
¹⁰ European Southern Observatory, Karl-Schwarzschild Straße 2, 85748 Garching bei München, Germany
¹¹ Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, PR China
¹² Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, PR China
¹³ Korea Astronomy & Space Science Institute, 776 Daedukdae-ro, Yuseong-gu, Daejeon 305-348, Republic of Korea
¹⁴ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
¹⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁶ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
¹⁷ Finnish Centre for Astronomy with ESO (FINCA), Väisäläntie 20, 21500 Piikkiö, Finland
¹⁸ Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
¹⁹ School of Physical Sciences, Faculty of Science, Technology, Engineering and Mathematics, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
²⁰ Unidad de Astronomía, Fac. de Ciencias Básicas, Universidad de Antofagasta, Avda. U. de Antofagasta, 02800 Antofagasta, Chile
²¹ Department of Physics, University of Rome Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
²² INAF – Astrophysical Observatory of Turin, via Osservatorio 20, 10025 Pino Torinese, Italy
²³ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
²⁴ Department of Physics, Sharif University of Technology, PO Box 11155-9161 Tehran, Iran
²⁵ Department of Physics, Isfahan University of Technology, 84156-83111 Isfahan, Iran
²⁶ Institut d’Astrophysique et de Géophysique, Allée du 6 Août 19c, Sart Tilman, Bât. B5c, 4000 Liège, Belgium
²⁷ Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
²⁸ Argelander-Institut für Astronomie, Auf dem Hgel, 71, 53121 Bonn, Germany

Received: 29 August 2017
Accepted: 21 September 2017

Abstract

Context. The formation and dynamical history of hot Jupiters is currently debated, with wide stellar binaries having been suggested as a potential formation pathway. Additionally, contaminating light from both binary companions and unassociated stars can significantly bias the results of planet characterisation studies, but can be corrected for if the properties of the contaminating star are known.

Aim. We search for binary companions to known transiting exoplanet host stars, in order to determine the multiplicity properties of hot Jupiter host stars. We also search for and characterise unassociated stars along the line of sight, allowing photometric and spectroscopic observations of the planetary system to be corrected for contaminating light.

Methods. We analyse lucky imaging observations of 97 Southern hemisphere exoplanet host stars, using the Two Colour Instrument on the Danish 1.54 m telescope. For each detected companion star, we determine flux ratios relative to the planet host star in two passbands, and measure the relative position of the companion. The probability of each companion being physically associated was determined using our two-colour photometry.

Results. A catalogue of close companion stars is presented, including flux ratios, position measurements, and estimated companion star temperature. For companions that are potential binary companions, we review archival and catalogue data for further evidence. For WASP-77AB and WASP-85AB, we combine our data with historical measurements to determine the binary orbits, showing them to be moderately eccentric and inclined to the line of sight (and hence planetary orbital axis). Combining our survey with the similar Friends of Hot Jupiters survey, we conclude that known hot Jupiter host stars show a deficit of high mass stellar companions compared to the field star population; however, this may be a result of the biases in detection and target selection by ground-based surveys.