1203.2615 (Andrew J. Skemer et al.)

First Light LBT AO Images of HR 8799 bcde at 1.65 and 3.3 Microns: New Discrepancies between Young Planets and Old Brown Dwarfs    [PDF]

Andrew J. Skemer, Philip M. Hinz, Simone Esposito, Adam Burrows, Jarron Leisenring, Michael Skrutskie, Silvano Desidera, Dino Mesa, Carmelo Arcidiacono, Filippo Mannucci, Timothy J. Rodigas, Laird Close, Don McCarthy, Craig Kulesa, Guido Agapito, Daniel Apai, Javier Argomedo, Vanessa Bailey, Konstantina Boutsia, Runa Briguglio, Guido Brusa, Lorenzo Busoni, Riccardo Claudi, Joshua Eisner, Luca Fini, Katherine B. Follette, Peter Garnavich, Raffaele Gratton, Juan Carlos Guerra, John M. Hill, William F. Hoffmann, Terry Jones, Megan Krejny, Jared Males, Elena Masciadri, Michael R. Meyer, Douglas L. Miller, Katie Morzinski, Matthew Nelson, Enrico Pinna, Alfio Puglisi, Sascha P. Quanz, Fernando Quiros-Pacheco, Armando Riccardi, Paolo Stefanini, Vidhya Vaitheeswaran, John C. Wilson, Marco Xompero

As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study the physical properties of several planets in parallel. In this paper, we image all four of the HR 8799 planets at H-band and 3.3 microns with the new LBT adaptive optics system, PISCES, and LBTI/LMIRCam. Our images offer an unprecedented view of the system, allowing us to obtain H and 3.3$ micron photometry of the innermost planet (for the first time) and put strong upper-limits on the presence of a hypothetical fifth companion. We find that all four planets are unexpectedly bright at 3.3 microns compared to the equilibrium chemistry models used for field brown dwarfs, which predict that planets should be faint at 3.3 microns due to CH4 opacity. We attempt to model the planets with thick-cloudy, non-equilibrium chemistry atmospheres, but find that removing CH4 to fit the 3.3 micron photometry increases the predicted L' (3.8 microns) flux enough that it is inconsistent with observations. In an effort to fit the SED of the HR 8799 planets, we construct mixtures of cloudy atmospheres, which are intended to represent planets covered by clouds of varying opacity. In this scenario, regions with low opacity look hot and bright, while regions with high opacity look faint, similar to the patchy cloud structures on Jupiter and L/T transition brown-dwarfs. Our mixed cloud models reproduce all of the available data, but self-consistent models are still necessary to demonstrate their viability.

View original: http://arxiv.org/abs/1203.2615