SIMBAD references

2009ApJ...702..154S - Astrophys. J., 702, 154-170 (2009/September-1)

The 0.8-14.5 µm spectra of mid-l to Mid-T dwarfs: diagnostics of effective temperature, grain sedimentation, gas transport, and surface gravity.


Abstract (from CDS):

We present new 5.2-14.5 µm low-resolution spectra of 14 mid-L to mid-T dwarfs. We also present new 3.0-4.1 µm spectra for five of these dwarfs. These data are supplemented by existing red and near-infrared spectra (∼0.6-2.5 µm), as well as red through mid-infrared spectroscopy of seven other L and T dwarfs presented by Cushing et al. We compare these spectra to those generated from the model atmospheres of Saumon & Marley. The models reproduce the observed spectra well, except in the case of one very red L3.5 dwarf, 2MASS J22244381-0158521. The broad wavelength coverage allows us to constrain almost independently the four parameters used to describe these photospheres in our models: effective temperature (Teff), surface gravity, grain sedimentation efficiency (fsed), and vertical gas transport efficiency (Kzz). The CH4 bands centered at 2.2, 3.3, and 7.65 µm and the CO band at 2.3 µm are sensitive to Kzz, and indicates that chemical mixing is important in all L and T dwarf atmospheres. The sample of L3.5 to T5.5 dwarfs spans the range 1800 K≳ Teff≳1000 K, with an L-T transition (spectral types L7 to T4) that lies between 1400 and 1100 K for dwarfs with typical near-infrared colors; bluer and redder dwarfs can be 100 K warmer or cooler, respectively, when using infrared spectral types. When using optical spectral types, the bluer dwarfs have more typical Teff values as they tend to have earlier optical spectral types. In this model analysis, fsed increases rapidly between types T0 and T4, indicating that increased sedimentation can explain the rapid disappearance of clouds at this stage of brown dwarf evolution. There is a suggestion that the transition to dust-free atmospheres happens at lower temperatures for lower gravity dwarfs.

Abstract Copyright:

Journal keyword(s): stars: individual (2MASS J00361617+1821104, 2MASS J05591914-1404488, 2MASS J08251968+2115521, 2MASS J09083803+5032088, 2MASS J15074769-1627386, 2MASS J22244381-0158521, 2MASS J22443167+2043433, 2MASS J22541892+3123498, DENIS-P J025503.3-470049, SDSS J000013.54+255418.6, SDSS J075840.32+324723.3, SDSS J080531.83+481233.1, SDSS J085758.44+570851.4) - stars: individual (SDSS J105213.50+442255.6AB, SDSS J111009.99+011613.0, SDSS J115553.85+055957.5, SDSS J120747.17+024424.8, SDSS J125453.90-012247.5, SDSS J133148.88-011652.5, SDSS J151643.00+305344.3, SDSS J152039.82+354619.8) - stars: low-mass, brown dwarfs

Simbad objects: 30

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