The Sonora Substellar Atmosphere Models. VI. Red Diamondback: Extending Diamondback with SPHINX for Brown Dwarf Early Evolution
Claire Davis, Jonathan J. Fortney, Aishwarya Iyer, Sagnick Mukherjee, Caroline Morley, Mark S. Marley, Michael R. Line, Philip S. Muirhead
Abstract
Abstract We extend the Sonora Diamondback brown dwarf evolution models to higher effective temperatures to treat the evolution of younger, higher-mass objects. Due to an upper temperature limit of T eff = 2400 K in the original Sonora Diamondback model grid, high-mass objects ( M ≥ 0.05 M ⊙ = 52.4 M J ) were limited to ages of ≳100 Myr. To include the early evolution of brown dwarfs at T eff > 2400 K, we use existing and new SPHINX cloud-free model atmosphere calculations of temperature structures of M-type atmospheres. These atmospheres range from T eff 2000 to 4000 K, log( g ) 3.0 to 5.5, and metallicity [M/H] −0.5 to +0.5. This combination of Diamondback and SPHINX atmospheres, with a transition across T eff 2000–2400 K, allows us to calculate evolution tracks, and infrared photometry and colors, for ages >1 Myr and masses from above the hydrogen-burning minimum mass down to planetary masses. The Hayashi phase of massive brown dwarf evolution (ages < 10–100 Myr) at low surface gravity leads to nearly constant T eff values, at effective temperatures much lower than would be obtained from simply extrapolating backward from evolution tracks at older ages.