N. Miller et al. 2009 ApJ 702 1413 doi:10.1088/0004-637X/702/2/1413
N. Miller1, J. J. Fortney1 and B. Jackson2
Show affiliationsWe examine the radius evolution of close in giant planets with a planet evolution model that couples the orbital-tidal and thermal evolution. For 45 transiting systems, we compute a large grid of cooling/contraction paths forward in time, starting from a large phase space of initial semimajor axes and eccentricities. Given observational constraints at the current time for a given planet (semimajor axis, eccentricity, and system age), we find possible evolutionary paths that match these constraints, and compare the calculated radii to observations. We find that tidal evolution has two effects. First, planets start their evolution at larger semimajor axis, allowing them to contract more efficiently at earlier times. Second, tidal heating can significantly inflate the radius when the orbit is being circularized, but this effect on the radius is short-lived thereafter. Often circularization of the orbit is proceeded by a long period while the semimajor axis slowly decreases. Some systems with previously unexplained large radii that we can reproduce with our coupled model are HAT-P-7, HAT-P-9, WASP-10, and XO-4. This increases the number of planets for which we can match the radius from 24 (of 45) to as many as 35 for our standard case, but for some of these systems we are required to be viewing them at a special time around the era of current radius inflation. This is a concern for the viability of tidal inflation as a general mechanism to explain most inflated radii. Also, large initial eccentricities would have to be common. We also investigate the evolution of models that have a floor on the eccentricity, as may be due to a perturber. In this scenario, we match the extremely large radius of WASP-12b. This work may cast some doubt on our ability to accurately determine the interior heavy element enrichment of normal, noninflated close in planets, because of our dearth of knowledge about these planets' previous orbital-tidal histories. Finally, we find that the end state of most close in planetary systems is disruption of the planet as it moves ever closer to its parent star.
Issue 2 (2009 September 10)
Received 2009 May 4, accepted for publication 2009 July 6
Published 2009 August 21
N. Miller et al. 2009 ApJ 702 1413
D Sinden and G H M van der Heijden 2009 J. Phys. A: Math. Theor. 42 375207
Elbio Dagotto et al 2008 J. Phys.: Condens. Matter 20 434224
Nelson Max et al 2009 J. Phys.: Conf. Ser. 180 012087
Stanislav Babak et al 2008 Class. Quantum Grav. 25 114037
Kevin Elkins et al 2005 J. Phys. D: Appl. Phys. 38 2306
Jongbae Kim 1998 J. Phys. G: Nucl. Part. Phys. 24 1881
M Barbieri et al 2009 New J. Phys. 11 093012
D-X Ye et al 2002 Nanotechnology 13 615
Gregory Boverman et al 2007 Phys. Med. Biol. 52 3619