相关论文: Impact of granulation effects on the use of Balmer…
Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and…
Context. Synthetic model atmosphere calculations are still the most commonly used tool when determining precise stellar parameters and stellar chemical compositions. Besides three-dimensional models that consistently solve for hydrodynamic…
Balmer lines are an important diagnostic of stellar atmospheric structure, since they are formed at a wide range of depths within the atmosphere. The different Balmer lines are formed at slightly different depths making them useful…
An analysis of H alpha and H beta spectra in a sample of 30 cool dwarf and subgiant stars is presented using MARCS model atmospheres based on the most recent calculations of the line opacities. A detailed quantitative comparison of the…
The atmospheres of cool main-sequence stars are structured by convective flows from the convective envelope that penetrate the optically thin layers and lead to structuring of the stellar atmospheres analogous to solar granulation. The…
We show how previous works (Fuhrmann et al., van 't Veer-Menneret & Megessier) demonstrate the efficiency of the use of Balmer line profiles for effective temperature determination. In agreement with them, we insist on the physical interest…
The new generation of 3D hydrodynamical model atmospheres have been employed to study the impact of a realistic treatment of stellar convection on element abundance determinations of globular cluster stars for a range of atomic and…
A major weakness in one-dimensional (1D) stellar structure and evolution modeling is the simplified treatment of convection, which leads to erroneous near-surface stratification and considerable uncertainties in predicted effective…
Context. The surface structures and dynamics of cool stars are characterized by the presence of convective motions and turbulent flows which shape the emergent spectrum. Aims. We used realistic three-dimensional radiative hydrodynamical…
Studies of the isotopic composition of magnesium in cool stars have so far relied upon the use of one-dimensional (1D) model atmospheres. Since the isotopic ratios derived are based on asymmetries of optical MgH lines, it is important to…
Stellar models utilising one-dimensional (1D), heuristic theories of convection fail to adequately describe the energy transport in superadiabatic layers. The improper modelling leads to well-known discrepancies between observed and…
We utilize state-of-the-art 3D hydrodynamical and classical 1D stellar model atmospheres to study the influence of convection on the formation properties of various atomic and molecular spectral lines in the atmospheres of four red giant…
In an effort to estimate the largely unknown effects of photospheric temperature fluctuations on spectroscopic abundance determinations, we have studied the problem of LTE line formation in the inhomogeneous solar photosphere based on…
We show that contrary to what is expected from 1D stationary model atmospheres, 3D hydrodynamical modeling predicts a considerable influence of convection on the spectral properties of late-type giants. This is due to the fact that…
During the recent years significant progress has been made in the modeling of red giant atmospheres with the aid of 3D hydrodynamical model atmosphere codes. In this contribution we provide an overview of selected results obtained in this…
Details of a theory of self-broadening of hydrogen lines are presented. The main features of the new theory are that the dispersive-inductive components of the interaction (van der Waals forces) have been included, and the resonance…
Stellar evolution codes play a major role in present-day astrophysics, yet they share common simplifications related to the outer layers of stars. We seek to improve on this by the use of results from realistic and highly detailed 3D…
We compare the results of Balmer-line calculations using recent theory and improved computational algorithms with those from the widely-used SYNTHE and BALMER9 routines. The resulting profiles are mostly indistinguishable. Good fits to the…
A sequence of pure-hydrogen CO5BOLD 3D model atmospheres of DA white dwarfs is presented for a surface gravity of log g = 8 and effective temperatures from 6000 to 13,000 K. We show that convective properties, such as flow velocities,…
Numerical 3D radiative (M)HD simulations of solar convection are used to understand the physical properties of the solar photosphere. To validate this approach, it is important to check that no excessive thermodynamic fluctuations arise as…