Multi-site campaign for transit timing variations of WASP-12 b: possible detection of a long-period signal of planetary origin⋆,⋆⋆,⋆⋆⋆
Toruń Centre for Astronomy, Nicolaus Copernicus University,
Gagarina 11, 87100
2 Institute of Astronomy, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse Blvd., 1784 Sofia, Bulgaria
3 Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergässchen 2–3, 07745 Jena, Germany
4 Michael Adrian Observatorium, Astronomie Stiftung Trebur, Trebur, Germany
5 University of Applied Sciences, Technische Hochschule Mittelhessen, Friedberg, Germany
6 Advanced Astronomy and Space Science Division, Korea Astronomy and Space Science Institute, Daejeon 305-348, Republic of Korea
7 Chungbuk National University Observatory, Cheongju 365-863, Republic of Korea
8 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
9 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
10 INAF – Astronomical Observatory of Capodimonte Salita Moiariello 16, 80131 Napoli, Italy
11 Societá Astronomica Lunae, Castelnuovo Magra, 19030 La Spezia, Italy
12 Unione Astrofili Italiani, Sezione Stelle Variabili – GRAV, Italy
13 Institute of Astronomy, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
14 Joint ALMA Observatory, Alonso de C’rdova 3107, Vitacura, Santiago, Chile
15 National Astronomical Observatory of Japan, 2-21-1, Osawa, Miaka, Tokyo, 181-8588, Japan
16 MTA CSFK, Konkoly Observatory, Konkoly-Thege Mikloś út 15−17, 1121 Budapest, Hungary
17 ELTE Gothard–Lendület Research Group, 9700 Szombathely, Hungary
18 Dept. of Exp. Physics & Astronomical Observatory, University of Szeged, 6720 Szeged, Hungary
19 Department of Physics, Eötvös University, Pázmány Péter Sétány 1/A, 1117 Budapest, Hungary
20 Astronomical Institute, Slovak Academy of Sciences, 05960 Tatranská Lomnica, Slovakia
21 Aryabhatta Research Institute of Observational Sciences(ARIES), Manora Peak, Nainital 263129, India
22 Institute of Astronomy, National Central University, 300 Jhongda Rd., Jhongli 32001, Taiwan
Accepted: 18 January 2013
Aims. The transiting planet WASP-12 b was identified as a potential target for transit-timing studies because a departure from a linear ephemeris has been reported in the literature. Such deviations could be caused by an additional planet in the system. We attempt to confirm the claimed variations in transit timing and interpret their origin.
Methods. We organised a multi-site campaign to observe transits by WASP-12 b in three observing seasons, using 0.5–2.6-metre telescopes.
Results. We obtained 61 transit light curves, many of them with sub-millimagnitude precision. The simultaneous analysis of the best-quality datasets allowed us to obtain refined system parameters, which agree with values reported in previous studies. The residuals versus a linear ephemeris reveal a possible periodic signal that may be approximated by a sinusoid with an amplitude of 0.00068 ± 0.00013 d and period of 500 ± 20 orbital periods of WASP-12 b. The joint analysis of timing data and published radial velocity measurements results in a two-planet model that explains observations better than do single-planet scenarios. We hypothesise that WASP-12 b might not be the only planet in the system, and there might be the additional 0.1 MJup body on a 3.6-d eccentric orbit. A dynamical analysis indicates that the proposed two-planet system is stable on long timescales.
Key words: planets and satellites: general / stars: individual: WASP-12 / planets and satellites: individual: WASP-12 b
Partly based on (1) data collected with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, (2) observations made at the Centro Astronómico Hispano Alemán (CAHA), operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC), (3) data collected with telescopes at the Rozhen National Astronomical Observatory, and (4) observations obtained with telescopes of the University Observatory Jena, which is operated by the Astrophysical Institute of the Friedrich-Schiller-University.
Tables 2 and 3 are available in electronic form at http://www.aanda.org
Light curves are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/551/A108
© ESO, 2013