Multi-site campaign for transit timing variations of WASP-12 b : possible detection of a long-period signal of planetary origin

Maciejewski, G. and Dimitrov, D. and Seeliger, M. and Raetz, St. and Bukowiecki, Ł. and Kitze, M. and Errmann, R. and Nowak, G. and Niedzielski, A. and Popov, V. and Marka, C. and Goździewski, K. and Neuhäuser, R. and Ohlert, J. and Hinse, T. C. and Lee, J. W. and Lee, C. -U. and Yoon, J. -N. and Berndt, A. and Gilbert, H. and Ginski, Ch. and Hohle, M. M. and Mugrauer, M. and Röll, T. and Schmidt, T. O. B. and Tetzlaff, N. and Mancini, L. and Southworth, J. and Dall'Ora, M. and Ciceri, S. and Benkő, József and Sárneczky, Krisztián and Szabó M., Gyula (2013) Multi-site campaign for transit timing variations of WASP-12 b : possible detection of a long-period signal of planetary origin. ASTRONOMY & ASTROPHYSICS, 551. ISSN 0004-6361

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Abstract

Aims. The transiting planet WASP-12 b was identified as a potential target for transit timing studies because a departure from a linear ephemeris was reported in the literature. Such deviations could be caused by an additional planet in the system. We attempt to confirm the existence of claimed variations in transit timing and interpret its 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 which better explains observations than single-planet scenarios. We hypothesize that WASP-12 b might be not 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 over long timescales.

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