Theory of Circumstellar Envelopes

Wehrsě, R.

doi:10.1007/978-94-009-3887-8_71

Cited by 3 publications

(2 citation statements)

References 18 publications

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“…Additional species can be easily included if required by, for instance, a different mixture. The results of the adiabatic gradient calculations are in very good agreement with the results obtained through numerical differentiation of the entropy by Unsöld (1968) and by Wehrse (1974).…”

Section: Eos and Adiabatic Gradientsupporting

confidence: 82%

“…The adiabatic gradient is calculated analytically including the most important species; H I-II, He I-II, H 2 , CO, and electrons (as well as a number of species of secondary importance, for a total of 12 species); based on an algorithm developed by Wehrse (1977). Details of the numerical application of this algorithm may also be found in Allard (1990).…”

Section: Eos and Adiabatic Gradientmentioning

confidence: 99%

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Model atmospheres for M (sub)dwarf stars. 1: The base model grid

Hauschildt

1995

ApJ

403

356

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We have calculated a grid of more than 700 model atmospheres valid for a wide range of parameters encompassing the coolest known M dwarfs, M subdwarfs and brown dwarf candidates: 1500 ≤ T eff ≤ 4000 K, 3.5 ≤ log(g) ≤ 5.5, and −4.0 ≤ [M/H] ≤ +0.5.Our equation of state includes 105 molecules and up to 27 ionization stages of 39 elements. In the calculations of the base grid of model atmospheres presented here, we include over 300 molecular bands of 4 molecules (TiO, VO, CaH, FeH) in the JOLA approximation, the water opacity of Ludwig (1971), collision induced opacities, b-f and f-f atomic processes, as well as about 2 million spectral lines selected from a list with more than 42 million atomic and 24 million molecular (H 2 , CH, NH, OH, MgH, SiH, C 2 , CN, CO, SiO) lines. High-resolution synthetic spectra are obtained using an opacity sampling method. The model atmospheres and spectra are calculated with the generalized stellar atmosphere code PHOENIX, assuming LTE, plane-parallel geometry, energy (radiative plus convective) conservation, and hydrostatic equilibrium.The model spectra give close agreement with observations of M dwarfs across a wide spectral range from the blue to the near-IR, with one notable exception: the fit to the water bands. We discuss several practical applications of our model grid, e.g., broadband colors derived from the synthetic spectra. In light of current efforts to identify genuine brown dwarfs, we also show how low-resolution spectra of cool dwarfs vary with surface gravity, and how the high-resolution line profile of the Li I resonance doublet depends on the Li abundance.

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Section: Eos and Adiabatic Gradientsupporting

confidence: 82%

Section: Eos and Adiabatic Gradientmentioning

confidence: 99%