Physical Properties of the 0.94-Day Period Transiting Planetary System WASP-18
English
Southworth, John[Astrophysics Group, Keele University, Newcastle-under Lyme, ST5 5BG, UK]
Hinse, T. C.[Armagh Observatory, College Hill, Armagh, BT61 9DG, UK ; Niels Bohr Institute and Centre for Star and Planet Formation, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen Ø, Denmark]
Dominik, M.[SUPA, University of St. Andrews, School of Physics & Astronomy, North Haugh, St. Andrews, KY16 9SS, UK ; Royal Society University Research Fellow.]
Glitrup, M.[Department of Physics & Astronomy, Aarhus University, Ny Munkegade, 8000 Aarhus C, Denmark]
Jørgensen, U. G.[Niels Bohr Institute and Centre for Star and Planet Formation, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen Ø, Denmark]
Liebig, C.[Astronomisches Rechen-Institut, Zentrum für Astronomie, Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany]
Mathiasen, M.[SUPA, University of St. Andrews, School of Physics & Astronomy, North Haugh, St. Andrews, KY16 9SS, UK]
Anderson, D. R.[Astrophysics Group, Keele University, Newcastle-under Lyme, ST5 5BG, UK]
Bozza, V.[Dipartimento di Fisica "E. R. Caianiello," Università di Salerno, Baronissi, Italy ; Instituto Nazionale di Fisica Nucleare, Sezione di Napoli, Italy]
Browne, P.[SUPA, University of St. Andrews, School of Physics & Astronomy, North Haugh, St. Andrews, KY16 9SS, UK]
Burgdorf, M.[Deutsches SOFIA Institut, NASA Ames Research Center, Mail Stop 211-3, Moffett Field, CA 94035, USA]
Calchi Novati, S.[Dipartimento di Fisica "E. R. Caianiello," Università di Salerno, Baronissi, Italy ; Instituto Nazionale di Fisica Nucleare, Sezione di Napoli, Italy]
Finet, François[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Harpsøe, K.[Niels Bohr Institute and Centre for Star and Planet Formation, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen Ø, Denmark]
Maier, G.[Astronomisches Rechen-Institut, Zentrum für Astronomie, Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany]
Mancini, L.[Dipartimento di Fisica "E. R. Caianiello," Università di Salerno, Baronissi, Italy ; Instituto Nazionale di Fisica Nucleare, Sezione di Napoli, Italy]
Maxted, P. F. L.[Astrophysics Group, Keele University, Newcastle-under Lyme, ST5 5BG, UK]
Rahvar, S.[Department of Physics, Sharif University of Technology, Tehran, Iran]
Ricci, Davide[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Scarpetta, G.[Dipartimento di Fisica "E. R. Caianiello," Università di Salerno, Baronissi, Italy ; Instituto Nazionale di Fisica Nucleare, Sezione di Napoli, Italy]
Skottfelt, J.[Niels Bohr Institute and Centre for Star and Planet Formation, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen Ø, Denmark]
Snodgrass, C.[European Southern Observatory, Casilla 19001, Santiago 19, Chile]
Surdej, Jean[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Zimmer, F.[Astronomisches Rechen-Institut, Zentrum für Astronomie, Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany]
[en] planetary systems ; stars: individual: WASP-18
[en] 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 M [SUB]b[/SUB] = 10.43 ± 0.30 ± 0.24 M [SUB]Jup[/SUB] and R [SUB]b[/SUB] = 1.165 ± 0.055 ± 0.014 R [SUB]Jup[/SUB] (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 (M [SUB]b[/SUB] > 3 M [SUB]Jup[/SUB]) 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. Based on data collected by MiNDSTEp with the Danish 1.54 m telescope at the ESO La Silla Observatory.
[Astrophysics Group, Keele University, Newcastle-under Lyme, ST5 5BG, UK]
