Transits in the planetary system WASP-4 were recently found to occur 80s 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. 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-4b 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.
@article{arxiv.1907.08269,
title = {Transit timing variations in the WASP-4 planetary system},
author = {John Southworth and M. Dominik and U. G. Jorgensen and M. I. Andersen and V. Bozza and M. J. Burgdorf and G. D'Ago and S. Dib and R. Figuera Jaimes and Y. I. Fujii and S. Gill and L. K. Haikala and T. C. Hinse and M. Hundertmark and E. Khalouei and H. Korhonen and P. Longa-Pena and L. Mancini and N. Peixinho and M. Rabus and S. Rahvar and S. Sajadian and J. Skottfelt and C. Snodgrass and P. Spyratos and J. Tregloan-Reed and E. Unda-Sanzana and C. von Essen},
journal= {arXiv preprint arXiv:1907.08269},
year = {2019}
}
Comments
Accepted for publication to MNRAS Main Journal. 7 pages, 2 colour figures, 1 table. Version 2 is the revised version after the refereeing process, which includes changes to some of the conclusions of the paper