Related papers: Line broadening and the solar opacity problem
The influence of departures from local thermodynamic equilibrium (LTE) on neutral sulfur lines is considered. A grid of corrections is proposed to take into account the influence of departures from LTE for neutral sulfur lines in the…
We construct seismic models of the four double-mode radial $\delta$ Scuti stars adopting opacities from three databases: OPAL, OP and OPLIB. The aim is to find the models that fit the observed frequencies of the two radial modes and have…
The luminosity evolution of stars with highly condensed cores surrounded by nuclear-burning shell(s) is analytically investigated with the aid of homology relations. With respect to earlier works using a similar approach (e.g. Refsdal &…
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…
Spectra of late-type stars are usually analyzed with static model atmospheres in local thermodynamic equilibrium (LTE) and a homogeneous plane-parallel or spherically symmetric geometry. The energy balance requires particular attention, as…
We introduce a novel algorithm, $\textit{COD}$ -- Compact Opacity Distribution, for shape reconstruction of a celestial body that has been observed to occult a star, using the photometric time-series observations of the occultation.…
In the Sun, the two forbidden [OI] lines at 630 and 636 nm were previously found to provide discrepant oxygen abundances. aims: We investigate whether this discrepancy is peculiar to the Sun or whether it is also observed in other stars.…
Massive stars show a variety of spectral variability: presence of discrete absorption components in UV P-Cygni profiles, optical line profile variability, X-ray variability, radial velocity modulations. Our goal is to study the spectral…
Stars grow by accreting gas that has an evolving composition owing to the growth and inward drift of dust (pebble wave), the formation of planetesimals and planets, and the selective removal of hydrogen and helium by disk winds. We…
During solar flares, spectral lines formed in the photosphere have been shown to exhibit changes to their profiles despite the challenges of energy transfer to these depths. Recent work has shown that deep-forming spectral lines are subject…
We present a comparative spectral analysis to explore the ability of a cooler Sun model to accurately capture the spectral line shape changes caused by Sunspots. In the search for small Earth-like planets, the effects of stellar surface…
The self-consistent inclusion of plasma effects in opacity calculations is a significant modeling challenge. As density increases, such effects can no longer be treated perturbatively. Building on a recently published model that addresses…
We present a new approach to study the properties of the sun. We consider small variations of the physical and chemical properties of the sun with respect to Standard Solar Model predictions and we linearize the structure equations to…
Winds of massive stars have density inhomogeneities (clumping) that may affect the formation of spectral lines in different ways, depending on their formation region. Most of previous and current spectroscopic analyses have been performed…
We examine contributions of second order physical processes to results of stellar evolution calculations amenable to direct observational testing. In the first paper in the series (Young et al. 2001) we established baseline results using…
\textbf{Scaling formulas were} deduced to describe the relations between the fundamental stellar parameters and the mean \textbf{linewidth and lifetime} of solar-like oscillations of stars. The mean \textbf{linewidth and} lifetime of…
We evaluate the logarithmic derivative of the depth of the solar convective zone with respect to the logarithm of the radiative opacity. We use this expression to show that the radiative opacity near the base of the solar convective zone…
Context. Comparison studies of Sun-like stars with the Sun suggest an anomalously low photometric variability of the Sun compared to Sun-like stars with similar magnetic activity. Comprehensive understanding of stellar variability is…
The frequency difference between a model used only two-point interpolation of opacity and a model used piecewise linear interpolation of opacity is of the order of several microHertz at a certain stage, which is almost 10 times worse than…
Context: State of the art quantitative spectroscopy of OB-stars compares synthetic spectra (calculated by means of 1D, spherically symmetric computer codes) with observations. Certain stellar atmospheres, however, show strong deviations…