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Physical properties of the 0.94-day period transiting planetary system WASP-18

Southworth, John; Hinse, T. C.; Dominik, M.; Glitrup, M.; Jørgensen, U. G.; Liebig, C.; Mathiasen, M.; Anderson, D. R.; Bozza, V.; Browne, P.; Burgdorf, M.; Calchi Novati, S.; Dreizler, S.; Finet, F.; Harpsøe, K.; Hessman, F.; Hundertmark, M.; Maier, G.; Mancini, L.; Maxted, P. F. L.; Rahvar, S.; Ricci, D.; Scarpetta, G.; Skottfelt, J.; Snodgrass, C.; Surdej, J. and Zimmer, F. (2009). Physical properties of the 0.94-day period transiting planetary system WASP-18. Astrophysical Journal, 707(1) pp. 167–172.

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We present high-precision photometry of five consecutive transits of WASP-18, an extrasolar planetary system with one of the shortest orbital periods known. Through the use of telescope defocusing we achieve a photometric precision of 0.47-0.83 mmag per observation over complete transit events. The data are analyzed using the JKTEBOP code and three different sets of stellar evolutionary models. We find the mass and radius of the planet to be Mb = 10.43 ± 0.30 ± 0.24 MJup and Rb = 1.165 ± 0.055 ± 0.014 RJup (statistical and systematic errors), respectively. The systematic errors in the orbital separation and the stellar and planetary masses, arising from the use of theoretical predictions, are of a similar size to the statistical errors and set a limit on our understanding of the WASP-18 system. We point out that seven of the nine known massive transiting planets (Mb > 3 MJup) have eccentric orbits, whereas significant orbital eccentricity has been detected for only four of the 46 less-massive planets. This may indicate that there are two different populations of transiting planets, but could also be explained by observational biases. Further radial velocity observations of low-mass planets will make it possible to choose between these two scenarios.

Item Type: Journal Item
Copyright Holders: 2009 The American Astronomical Society.
ISSN: 1538-4357
Keywords: planetary systems; stars
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Centre for Electronic Imaging (CEI)
Item ID: 43097
Depositing User: Colin Snodgrass
Date Deposited: 10 Jun 2015 14:37
Last Modified: 07 Dec 2018 10:31
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