Transit timing variations in the WASP-4 planetary system

John Southworth, M. Dominik, U. G. Jorgensen, M. I. Andersen, V. Bozza, M. J. Burgdorf, G. D'Ago, S. Dib, R. Figuera Jaimes, Y. I. Fujii, S. Gill, L. K. Haikala, T. C. Hinse, M. Hundertmark, E. Khalouei, H. Korhonen, P. Longa-Peña, L. Mancini, N. Peixinho, M. RabusS. Rahvar, S. Sajadian, J. Skottfelt, C. Snodgrass, P. Spyratos, J. Tregloan-Reed, E. Unda-Sanzana, C. von Essen

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Transits in the planetary system WASP-4 were recently found to occur 80 s earlier than expected in observations from the TESS satellite. We present 22 new times of mid-transit that confirm the existence of transit timing variations, and are well fitted by a quadratic ephemeris with period decay dP/dt = −9.2 ± 1.1 ms yr−1. We rule out instrumental issues, stellar activity and the Applegate mechanism as possible causes. The light-time effect is also not favoured due to the non-detection of changes in the systemic velocity. Orbital decay and apsidal precession are plausible but unproven. WASP-4 b is only the third hot Jupiter known to show transit timing variations to high confidence. We discuss a variety of observations of this and other planetary systems that would be useful in improving our understanding of WASP-4 in particular and orbital decay in general.
Original languageEnglish
Pages (from-to)4230-4236
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date19 Sept 2019
Publication statusPublished - Dec 2019


  • Planetary systems
  • Stars: fundemental parameters
  • Stars:activity
  • Stars: individual: WASP-4


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