High-precision photometry by telescope defocussing. II. The transiting planetary system WASP-4
Abstract
We present and analyse light curves of four transits of the Southern hemisphere extrasolar planetary system WASP-4, obtained with a telescope defocussed so the radius of each point spread function was 17 arcsec (44 pixels). This approach minimises both random and systematic errors, allowing us to achieve scatters of between 0.60 and 0.88 mmag per observation over complete transit events. The light curves are augmented by published observations and analysed using the JKTEBOP code. The results of this process are combined with theoretical stellar model predictions to derive the physical properties of the WASP-4 system. We find that the mass and radius of the planet are M_b = 1.289 {+0.090 -0.090} {+0.039 -0.000} MJup and R_b = 1.371 {+0.032 -0.035} {+0.021 -0.000} RJup, respectively (statistical and systematic uncertainties). These quantities give a surface gravity and density of g_b = 17.03 +0.97 -0.54 m/s2 and rho_b = 0.500 {+0.032 -0.021} {+0.000 -0.008} rhoJup, and fit the trends for short-period extrasolar planets to have relatively high masses and surface gravities. WASP-4 is now one of the best-quantified transiting extrasolar planetary systems, and significant further progress requires improvements to our understanding of the physical properties of low-mass stars.
Keywords
Cite
@article{arxiv.0907.3356,
title = {High-precision photometry by telescope defocussing. II. The transiting planetary system WASP-4},
author = {John Southworth and T. C. Hinse and M. J. Burgdorf and M. Dominik and A. Hornstrup and U. G. Jorgensen and C. Liebig and D. Ricci and C. C. Thone and T. Anguita and V. Bozza and S. Calchi Novati and K. Harpsoe and L. Mancini and G. Masi and M. Mathiasen and S. Rahvar and G. Scarpetta and C. Snodgrass and J. Surdej and M. Zub},
journal= {arXiv preprint arXiv:0907.3356},
year = {2015}
}
Comments
Accepted for publication in MNRAS. 8 pages plus appendix, 4 figures, 8 tables