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We discuss prospects of using multi-dimensional time-dependent simulations to study the atmospheres of brown dwarfs and extrasolar giant planets, including the processes of convection, radiation, dust formation, and rotation. We argue that…

Astrophysics · Physics 2009-11-13 Hans-G. Ludwig

We present a new generation of substellar atmosphere and evolution models, appropriate for application to studies of L, T, and Y-type brown dwarfs and self-luminous extrasolar planets. The atmosphere models describe the expected…

A number of brown dwarfs are now known to be variable with observed amplitudes as large as 10-30% at some wavelengths. While spatial inhomogeneities in cloud coverage and thickness are likely responsible for much of the observed…

Solar and Stellar Astrophysics · Physics 2014-04-24 Tyler D. Robinson , Mark S. Marley

Reliable modeling of the atmospheres of cool white dwarfs is crucial for understanding the atmospheric evolution of these stars and for accurate white dwarfs cosmochronology. Over the last decade {\it ab initio} modeling entered many…

Solar and Stellar Astrophysics · Physics 2015-05-20 Piotr M. Kowalski

Extrasolar planets appear in a chemical diversity unseen in our own solar system. Despite their atmospheres being cold, continuous and transient plasma processes do affect these atmosphere where clouds form with great efficiency. Clouds can…

Solar and Stellar Astrophysics · Physics 2018-09-26 Ch. Helling , I. Vorgul

Clouds and hazes are important throughout our solar system and in the atmospheres of brown dwarfs and extrasolar giant planets. Among the brown dwarfs, clouds control the colors and spectra of the L-dwarfs; the disappearance of clouds helps…

Astrophysics · Physics 2007-05-23 M. S. Marley , A. S. Ackerman

The spectra of brown dwarfs are key to exploring the chemistry and physics that take place in their atmospheres. Late-T dwarf spectra are particularly diagnostic due to their relatively cloud-free atmospheres and deep molecular bands. With…

Recent observations indicate potentially carbon-rich exoplanet atmospheres. Spectral fitting methods for brown dwarfs and exoplanets have invoked the C/O ratio as additional parameter but carbon-rich cloud formation modeling is a challenge…

Solar and Stellar Astrophysics · Physics 2021-06-04 Ch. Helling , D. Tootill , P. Woitke , E. K. H. Lee

Growing observational evidence has suggested active meteorology in atmospheres of brown dwarfs (BDs) and directly imaged extrasolar giant planets (EGPs). In particular, a number of surveys have shown that near-IR brightness variability is…

Solar and Stellar Astrophysics · Physics 2019-04-03 Xianyu Tan , Adam P. Showman

We present results from conducting a theoretical chemical analysis of a sample of benchmark companion brown dwarfs whose primary star is of type F, G or K. We summarize the entire known sample of these types of companion systems, termed…

Solar and Stellar Astrophysics · Physics 2024-01-23 Emily Calamari , Jacqueline K. Faherty , Channon Visscher , Marina E. Gemma , Ben Burningham , Austin Rothermich

The last few years has seen a dramatic increase in the number of exoplanets known and in the range of methods for characterising their atmospheric properties. At the same time, new discoveries of increasingly cooler brown dwarfs have pushed…

Earth and Planetary Astrophysics · Physics 2015-06-23 Jeremy Bailey

Dust formation in brown dwarf atmospheres is studied by utilising a model for driven turbulence in the mesoscopic scale regime. We apply a pseudo-spectral method where waves are created and superimposed within a limited wavenumber interval.…

Astrophysics · Physics 2007-05-23 Ch. Helling , R. Klein , P. Woitke , U. Nowak , E. Sedlmayr

The atmospheres of brown dwarfs orbiting in close proximity to their parent white dwarf represent some of the most extreme irradiated environments known. Understanding their complex dynamical mechanisms pushes the limits of theoretical and…

Solar and Stellar Astrophysics · Physics 2022-03-21 Elspeth K. H. Lee , Joshua D. Lothringer , Sarah L. Casewell , Daniel Kitzmann , Ben W. P. Lew , Yifan Zhou

We review several aspects of the calculation of exoplanet model atmospheres in the current era, with a focus on understanding the temperature-pressure profiles of atmospheres and their emitted spectra. Most of the focus is on gas giant…

Earth and Planetary Astrophysics · Physics 2018-04-24 Jonathan J. Fortney

Ground-based and spacecraft telescopic observations, combined with an intensive modeling effort, have greatly enhanced our understanding of hot giant planets and brown dwarfs over the past ten years. Although these objects are all fluid,…

Earth and Planetary Astrophysics · Physics 2020-12-09 Adam P. Showman , Xianyu Tan , Vivien Parmentier

Radio and X-ray emission from brown dwarfs suggest that an ionised gas and a magnetic field with a sufficient flux density must be present. We perform a reference study for late M-dwarfs, brown dwarfs and giant gas planet to identify which…

Earth and Planetary Astrophysics · Physics 2015-11-04 M. I. Rodriguez-Barrera , Ch. Helling , C. R. Stark , A. M. Rice

We aim at understanding the formation of cloud layers in quasi-static substellar atmospheres. The time-dependent description presented in (Helling & Woitke 2006) is a kinetic model describing nucleation, growth and evaporation. It is…

Astrophysics · Physics 2009-11-13 Ch. Helling , P. Woitke , W. -F. Thi

Electric discharges were detected directly in the cloudy atmospheres of Earth, Jupiter and Saturn, are debatable for Venus, and indirectly inferred for Neptune and Uranus in our solar system. Sprites (and other types of transient luminous…

Earth and Planetary Astrophysics · Physics 2015-06-12 Ch. Helling , M. Jardine , C. Stark , D. Diver

Theoretical analysis and observational evidences indicate that a brown dwarf with effective temperature greater than 1400 K would have dust cloud in its atmosphere. In this letter, we show that dust scattering should yield polarized…

Astrophysics · Physics 2009-11-07 Sujan Sengupta , Vinod Krishan

The atmospheres of brown dwarfs have been long observed to exhibit a multitude of non-equilibrium chemical signatures and spectral variability across the L, T and Y spectral types. We aim to investigate the link between the large-scale 3D…

Solar and Stellar Astrophysics · Physics 2023-06-14 Elspeth K. H. Lee , Xianyu Tan , Shang-Min Tsai