| 1. |
- Allard, F, et al.
(author)
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Model atmospheres and spectra: The role of dust
- 2003
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In: Proceedings of the International Astronomical Union (Brown Dwarfs). - 0074-1809. - 158381132X ; 211, s. 325-332
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Conference paper (peer-reviewed)abstract
- Brown dwarf atmospheres form molecules, then high temperature condensates (corundum, titanates, silicates, and iron compounds), and then low temperature condensates (ices) as they cool down over time. These produce large opacities which govern entirely their spectral energy distribution. Just as it is important to know molecular opacities (TiO, H2O, CH4, etc.) with accuracy, it is imperative to understand the interplay of processes (e.g. condensation, sedimentation, coagulation, convection) that determines the radial and size distribution of grains. Limiting case models have shown that young, hot brown (L) dwarfs form dust mostly in equilibrium, while at much cooler stages (late T dwarfs) all high temperature condensates have sedimented out of their photospheres. But this process is gradual and all intermediate classes of brown dwarfs can partly be understood in terms of partial sedimentation of dust. With new models accounting for these processes, we describe the effects they may have upon brown dwarf spectral properties.
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| 2. |
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| 3. |
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| 4. |
- Chu, H.S., et al.
(author)
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Discovery of Helical Magnetic Fields in AGN and CME and Ejection of Large Scale Magnetic Fields from AGN
- 2003
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In: Symposium - International astronomical union. - : International Astronomical Union. - 0074-1809. ; 214, s. 303-310
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Journal article (peer-reviewed)abstract
- Magnetic Fields are the crucial and most important ingredient involved in the processes of various violent activities in Active Galactic Nuclei and other celestial bodies. The generally accepted 2-sided symmetric-jets model of active galactic nuclei (AGN) does not include the magnetic fields. We present here the first direct detection of helical magnetic field in AGN, and the first direct detection of ejection of large scale magnetic fields from AGN. (CME) 2. The annular (helical) magnetic field is responsible for the collimation of the jet (through Pinch Effect) and may be of crucial importance for extraction of black hole rotational energy. 3. The CMEs are responsible for sporadic ejection of jet components in AGN, while the general accepted 2-sided jets pertain to the quiescent Jets. 4.Observations show that the CME with Asymmetric Jets can explain many phenomena and much of the morphological diversities in AGN.
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| 5. |
- Dravins, Dainis, et al.
(author)
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Absolute wavelength shifts - A new diagnostic for rapidly rotating stars
- 2004
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In: Stellar Rotation; IAU Symposium. - 0074-1809. ; :215, s. 27-32
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Conference paper (peer-reviewed)abstract
- Accuracies reached in space astrometry now permit. the accurate determination of astrometric radial velocities. without any use of spectroscopy. Knowing this true stellar motion, spectral shifts; intrinsic to stellar atmospheres can be identified, for instance gravitational redshifts and those caused by, velocity fields on stellar surfaces. The astrometric accuracy is independent. of any spectral complexity, such as the smeared-out line profiles of rapidly rotating stars. Besides a better determination of stellar velocities, this permits more precise studies of atmospheric dynamics, such as possible modifications of stellar surface convection (granulation) by rotation-induced forces, as well as a potential for observing meridional flows across stellar surfaces.
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| 7. |
- Gustafsson, Bengt
(author)
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High-precision astrometry and the modelling of stellar spectra
- 1995
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In: ASTRONOMICAL AND ASTROPHYSICAL OBJECTIVES OF SUB-MILLIARCSECOND OPTICAL ASTROMETRY. - 0074-1809. ; :166, s. 143-148
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Research review (pop. science, debate, etc.)abstract
- The impact of high-precision astrometry on modelling of stellar spectra and determination of fundamental stellar parameters for single stars is discussed. It is found to be considerable, but improvements in the understanding of stellar atmospheres, and in
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| 8. |
- Gustafsson, B, et al.
(author)
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What do we do when models don't fit? On model atmospheres and real stellar spectra
- 1997
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In: FUNDAMENTAL STELLAR PROPERTIES: THE INTERACTION BETWEEN OBSERVATION AND THEORY. - : KLUWER ACADEMIC PUBL. - 0074-1809. ; :189, s. 261-276
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Journal article (other academic/artistic)abstract
- Developments in the modelling of stellar atmospheres and results from the confrontation between calculated and observed fluxes and spectra are discussed. It is argued that, although impressive advances in the study of O-type, WR and cool star spectra have
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| 9. |
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| 10. |
- Maeder, A, et al.
(author)
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The evolution of massive stars
- 1997
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In: FUNDAMENTAL STELLAR PROPERTIES: THE INTERACTION BETWEEN OBSERVATION AND THEORY. - : KLUWER ACADEMIC PUBL. - 0074-1809. ; :189, s. 313-322
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Journal article (other academic/artistic)
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