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

D. Saumon; M. S. Marley; M. C. Cushing; S. K. Leggett; T. L. Roellig; K. Lodders; R. S. Freedman

doi:10.1086/505419

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

D. Saumon, M. S. Marley, M. C. Cushing, S. K. Leggett, T. L. Roellig, K. Lodders, R. S. Freedman

Research output: Contribution to journal › Article › peer-review

153 Scopus citations

Abstract

We 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: T_eff = 800-820 K, log 9 (cm s^-2) = 5.09-5.23, and log (L/L⊙) = -5.525 to -5.551. The Spitzer Infrared Spectrograph (IRS) spectrum shows prominent features of ammonia (NH₃) that can only be fitted by reducing the abundance of NH₃ by about 1 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.

Original language	English (US)
Pages (from-to)	552-557
Number of pages	6
Journal	Astrophysical Journal
Volume	647
Issue number	1 I
DOIs	https://doi.org/10.1086/505419
State	Published - Aug 10 2006
Externally published	Yes

Keywords

Stars: abundances
Stars: atmospheres
Stars: individual (Gliese 570D)
Stars: low-mass, brown dwarfs

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1086/505419

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title = "Ammonia as a tracer of chemical equilibrium in the T7.5 dwarf gliese 570D",

abstract = "We 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 = 800-820 K, log 9 (cm s-2) = 5.09-5.23, and log (L/L⊙) = -5.525 to -5.551. The Spitzer Infrared Spectrograph (IRS) spectrum shows prominent features of ammonia (NH3) that can only be fitted by reducing the abundance of NH3 by about 1 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.",

keywords = "Stars: abundances, Stars: atmospheres, Stars: individual (Gliese 570D), Stars: low-mass, brown dwarfs",

author = "D. Saumon and Marley, {M. S.} and Cushing, {M. C.} and Leggett, {S. K.} and Roellig, {T. L.} and K. Lodders and Freedman, {R. S.}",

year = "2006",

month = aug,

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doi = "10.1086/505419",

language = "English (US)",

volume = "647",

pages = "552--557",

journal = "Astrophysical Journal",

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publisher = "American Astronomical Society",

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TY - JOUR

T1 - Ammonia as a tracer of chemical equilibrium in the T7.5 dwarf gliese 570D

AU - Saumon, D.

AU - Marley, M. S.

AU - Cushing, M. C.

AU - Leggett, S. K.

AU - Roellig, T. L.

AU - Lodders, K.

AU - Freedman, R. S.

PY - 2006/8/10

Y1 - 2006/8/10

N2 - We 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 = 800-820 K, log 9 (cm s-2) = 5.09-5.23, and log (L/L⊙) = -5.525 to -5.551. The Spitzer Infrared Spectrograph (IRS) spectrum shows prominent features of ammonia (NH3) that can only be fitted by reducing the abundance of NH3 by about 1 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.

AB - We 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 = 800-820 K, log 9 (cm s-2) = 5.09-5.23, and log (L/L⊙) = -5.525 to -5.551. The Spitzer Infrared Spectrograph (IRS) spectrum shows prominent features of ammonia (NH3) that can only be fitted by reducing the abundance of NH3 by about 1 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.

KW - Stars: abundances

KW - Stars: atmospheres

KW - Stars: individual (Gliese 570D)

KW - Stars: low-mass, brown dwarfs

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U2 - 10.1086/505419

DO - 10.1086/505419

M3 - Article

AN - SCOPUS:33748463456

SN - 0004-637X

VL - 647

SP - 552

EP - 557

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1 I

ER -

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

Abstract

Keywords

ASJC Scopus subject areas

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