1 Max-Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
2 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
3 International Institute for Advanced Scientific Studies (IIASS), 84019 Vietri Sul Mare (SA), Italy
4 Department of Physics, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy
5 SUPA, University of St Andrews, School of Physics & Astronomy, North Haugh, St Andrews, KY16 9SS, UK
6 Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen Ø, Denmark
7 Centre for Star and Planet Formation, Geological Museum, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
8 Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
9 Astrophysics Group, University of Exeter, Stocker Road, EX4 4QL, Exeter, UK
10 Qatar Foundation, PO Box 5825, Doha, Qatar
11 Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Napoli, 80126 Napoli, Italy
12 Qatar Environment and Energy Research Institute, Qatar Foundation, Tornado Tower, Floor 19, PO Box 5825, Doha, Qatar
13 European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
14 Yunnan Observatories, Chinese Academy of Sciences, 650011 Kunming, PR China
15 Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 650011 Kunming, PR China
16 Korea Astronomy and Space Science Institute, Daejeon 305-348, Republic of Korea
17 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
18 Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
19 Department of Physics, Sharif University of Technology, PO Box 11155-9161 Tehran, Iran
20 Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
21 Las Cumbres Observatory Global Telescope Network, 6740B Cortona Drive, Goleta, CA 93117, USA
22 Institut d’Astrophysique et de Géophysique, Université de Liège, 4000 Liège, Belgium
23 School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
Received: 30 April 2014
Accepted: 28 June 2014
Context. The extrasolar planet WASP-67 b is the first hot Jupiter definitively known to undergo only partial eclipses. The lack of the second and third contact points in this planetary system makes it difficult to obtain accurate measurements of its physical parameters.
Aims. By using new high-precision photometric data, we confirm that WASP-67 b shows grazing eclipses and compute accurate estimates of the physical properties of the planet and its parent star.
Methods. We present high-quality, multi-colour, broad-band photometric observations comprising five light curves covering two transit events, obtained using two medium-class telescopes and the telescope-defocusing technique. One transit was observed through a Bessel-R filter and the other simultaneously through filters similar to Sloan g′r′i′z′. We modelled these data using jktebop. The physical parameters of the system were obtained from the analysis of these light curves and from published spectroscopic measurements.
Results. All five of our light curves satisfy the criterion for being grazing eclipses. We revise the physical parameters of the whole WASP-67 system and, in particular, significantly improve the measurements of the planet’s radius (Rb = 1.091 ± 0.046 RJup) and density (ρb = 0.292 ± 0.036 ρJup), as compared to the values in the discovery paper (Rb = 1.4 -0.2+0.3 RJup and ρb = 0.16 ± 0.08 ρJup). The transit ephemeris was also substantially refined. We investigated the variation of the planet’s radius as a function of the wavelength, using the simultaneous multi-band data, finding that our measurements are consistent with a flat spectrum to within the experimental uncertainties.
Key words: planetary systems / stars: fundamental parameters / techniques: photometric
Based on data collected with GROND at the MPG 2.2 m telescope and DFOSC at the Danish 1.54 m telescope.
Full Table 2 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/568/A127
© ESO, 2014