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Full-Text Articles in Astrophysics and Astronomy
Brown Dwarf Atmospheres At High Cadence And Spectral Resolution: A Speed Limit On Brown Dwarf Rotation And A Spectroscopic Atlas Of A 1050 K Atmosphere, Megan E. Tannock
Brown Dwarf Atmospheres At High Cadence And Spectral Resolution: A Speed Limit On Brown Dwarf Rotation And A Spectroscopic Atlas Of A 1050 K Atmosphere, Megan E. Tannock
Electronic Thesis and Dissertation Repository
Brown dwarfs are sub-stellar objects that form like stars but are not sufficiently massive to sustain hydrogen fusion in their cores. Characterized by cool, molecule-rich atmospheres, brown dwarfs demonstrate great diversity in spectroscopic appearance and share many properties with giant exoplanets. In this thesis I present two investigations: the first is a detailed photometric and spectroscopic study of the three most rapidly rotating brown dwarfs. The second examines a spectrum of a cool brown dwarf at unprecedented spectral resolution and signal-to-noise ratio to study the accuracy of theoretical model photospheres.
Photometric monitoring of brown dwarfs has revealed that periodic variability …
Following The Lithium: Tracing Li-Bearing Molecules Across Age, Mass, And Gravity In Brown Dwarfs, Ehsan Gharib-Nezhad, Mark S. Marley, Natasha E. Batalha, Channon Visscher, Richard S. Freedman, Roxana E. Lupu
Following The Lithium: Tracing Li-Bearing Molecules Across Age, Mass, And Gravity In Brown Dwarfs, Ehsan Gharib-Nezhad, Mark S. Marley, Natasha E. Batalha, Channon Visscher, Richard S. Freedman, Roxana E. Lupu
Faculty Work Comprehensive List
Lithium is an important element for the understanding of ultracool dwarfs because it is lost to fusion at masses above ∼68 MJ. Hence, the presence of atomic Li has served as an indicator of the nearby H-burning boundary at about 75 MJ between brown dwarfs and very low mass stars. Historically, the “lithium test,” a search for the presence of the Li line at 670.8 nm, has been a marker if an object has a substellar mass. While the Li test could, in principle, be used to distinguish masses of later-type L–T dwarfs, Li is predominantly no longer found as …
Cloud Busting: Enstatite And Quartz Clouds In The Atmosphere Of 2m2224-0158, Ben Burningham, Jacqueline K. Faherty, Eileen C. Gonzales, Mark S. Marley, Channon Visscher, Roxana Lupu, Josefine Gaarn, Michelle Fabienne Bieger, Richard Freedman, Didier Saumon
Cloud Busting: Enstatite And Quartz Clouds In The Atmosphere Of 2m2224-0158, Ben Burningham, Jacqueline K. Faherty, Eileen C. Gonzales, Mark S. Marley, Channon Visscher, Roxana Lupu, Josefine Gaarn, Michelle Fabienne Bieger, Richard Freedman, Didier Saumon
Faculty Work Comprehensive List
We present the most detailed data-driven exploration of cloud opacity in a substellar object to-date. We have tested over 60 combinations of cloud composition and structure, particle-size distribution, scattering model, and gas phase composition assumptions against archival 1–15μm spectroscopy for the unusually red L4.5 dwarf 2MASSW J2224438-015852 using the Brewster retrieval framework. We find that, within our framework, a model that includes enstatite and quartz cloud layers at shallow pressures, combined with a deep iron cloud deck fits the data best. This model assumes a Hansen distribution for particle sizes for each cloud, and Mie scattering. We retrieved particle effective …