High-precision photometry by telescope defocusing – VII. The ultrashort period planet WASP-103

John Southworth, L. Mancini, S. Ciceri, J. Budaj, M. Dominik, R. Figuera Jaimes, Troels Haugbølle, Uffe Gråe Jørgensen, Andrius Popovas, M. Rabus, S. Rahvar, C. von Essen, R. W. Schmidt, O. Wertz, K. A. Alsubai, V. Bozza, D. M. Bramich, S. Calchi Novati, G. D'Ago, T. C. HinseT. Henning, Markus Hundertmark, Diana Juncher, Heidi Helena Korhonen, Jesper Mirsa Skottfelt, C. Snodgrass, D. Starkey, J. Surdej

34 Citations (Scopus)

Abstract

We present 17 transit light curves of the ultrashort period planetary system WASP-103, a strong candidate for the detection of tidally-induced orbital decay. We use these to establish a high-precision reference epoch for transit timing studies. The time of the reference transit mid-point is now measured to an accuracy of 4.8 s, versus 67.4 s in the discovery paper, aiding future searches for orbital decay. With the help of published spectroscopic measurements and theoretical stellar models, we determine the physical properties of the system to high precision and present a detailed error budget for these calculations. The planet has a Roche lobe filling factor of 0.58, leading to a significant asphericity; we correct its measured mass and mean density for this phenomenon. A high-resolution Lucky Imaging observation shows no evidence for faint stars close enough to contaminate the point spread function of WASP-103. Our data were obtained in the Bessell RI and the SDSS griz passbands and yield a larger planet radius at bluer optical wavelengths, to a confidence level of 7.3σ. Interpreting this as an effect of Rayleigh scattering in the planetary atmosphere leads to a measurement of the planetary mass which is too small by a factor of 5, implying that Rayleigh scattering is not the main cause of the variation of radius with wavelength.

Original languageEnglish
JournalRoyal Astronomical Society. Monthly Notices
Volume447
Issue number1
Pages (from-to)711-721
Number of pages11
ISSN0035-8711
DOIs
Publication statusPublished - 11 Feb 2015

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