Ammonia as a tracer of chemical equilibrium in the T7.5 dwarf Gliese 570D

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dc.creatorSaumon, D.
dc.creatorMarley, M. S.
dc.creatorCushing, M. C.
dc.creatorLeggett, S. K.
dc.creatorRoellig, T. L.
dc.creatorLodders, K.
dc.creatorFreedman, R. S.
dc.date2006-05-22
dc.date.accessioned2026-07-07T10:39:04Z
dc.date.available2026-07-07T10:39:04Z
dc.descriptionWe present the first analysis of an optical to mid-infrared spectrum of the T7.5 dwarf Gliese 570D with model atmospheres, synthetic spectra, and brown dwarf evolution sequences. We obtain precise values for the basic parameters of Gl 570D: Teff=800 - 820K, log g (cm/s^2)=5.09 - 5.23, and log L/Lsun= -5.525 to -5.551. The Spitzer IRS spectrum shows prominent features of ammonia (NH3) that can only be fitted by reducing the abundance of NH3 by about one order of magnitude from the value obtained with chemical equilibrium models. We model departures from chemical equilibrium in the atmosphere of Gl 570D by considering the kinetics of nitrogen and carbon chemistry in the presence of vertical mixing. The resulting model spectrum reproduces the data very well.
dc.descriptionAccepted for publication in the ApJ. 10 pages, including 3 figures
dc.identifierhttps://arxiv.org/abs/astro-ph/0605563
dc.identifierhttp://arxiv.org/abs/astro-ph/0605563
dc.identifierAstrophys.J.647:552-557,2006
dc.identifierdoi:10.1086/505419
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/180898
dc.subjectAstrophysics
dc.titleAmmonia as a tracer of chemical equilibrium in the T7.5 dwarf Gliese 570D
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