A Systematic Study of Departures from Chemical Equilibrium in the Atmospheres of Substellar Mass Objects

• DOI: 10.1086/522107
• Publication Date: 2007-12-05T07:08:01Z
• Authors: Ivan Hubeny; Adam Burrows
• Keywords: Effective temperature; Chemical equilibrium; Surface gravity; Chemical species

We present a systematic study of the spectral consequences departures from chemical equilibrium in atmospheres L and T dwarfs, for even cooler dwarfs. The temperature/pressure profiles nonequilibrium models are fully consistent with chemistry. Our grid includes spectra effective temperatures 200 to 1800 K, three surface gravities, four possible values coefficient eddy diffusion radiative zone, different CO/CH4 reaction prescriptions. also provide clear cloudy model variants. find, keeping previous studies, that there essentially only two regions where effects can influence predicted spectrum. These M (~4-5 μm) N (8-14 bands due CO NH3, respectively. overabundance translates into flux suppressions at most ~40% between 600 K. effect is largest around Teff ≈ 1100 underabundance ammonia enhancements no more than ~20% range 300 lowest Teff. magnitude departure increases decreasing gravity, increasing coefficient, speed reaction. Although these modest, they lead better fits measured dwarf spectra. Furthermore, suppression band abundance disappears below ~500 partial above preserving M-band as useful diagnostic cool maintaining its importance searches brown dwarfs beyond