218 datasets found

This paper presents semiempirical models of various solar magnetic structures, extending from the photosphere to the chromosphere. The models have been derived from non-LTE...

We have obtained spectra for 1273 stars using the 0.9m coude feed telescope at Kitt Peak National Observatory. This telescope feeds the coude spectrograph of the 2.1m telescope....

We present a comprehensive analysis of DB white dwarfs drawn from the Sloan Digital Sky Survey, based on model fits to ugriz photometry and medium-resolution spectroscopy from...

As a result of competing physical mechanisms, the atmospheric composition of white dwarfs changes throughout their evolution, a process known as spectral evolution. Because of...

Atmospheric characterization through spectroscopic analysis, an essential tool of modern exoplanet science, can benefit significantly from the context provided by the interior...

Ultraviolet (UV) lines of molecular hydrogen have been observed in solar spectra for almost four decades, but the behavior of the molecular spectrum and its implications for...

Many parameters constraining the spectral appearance of exoplanets are still poorly understood. We therefore study the properties of irradiated exoplanet atmospheres over a wide...

We revisit the observed frequencies of carbon-enhanced metal-poor (CEMP) stars as a function of the metallicity in the Galaxy, using data from the literature with available...

We propose a method to distinguish between cloudy, hazy, and clear sky (free of clouds and hazes) exoplanet atmospheres that could be applicable to upcoming large aperture...

An accurate spectroscopic characterization of protonated oxirane has been carried out by means of state-of-the-art computational methods and approaches. The calculated...

We derived atmospheric parameters and spectroscopic abundances for C and O for a large sample of stars located in the Hertzsprung gap in the Hertzsprung-Russell diagram in order...

We present a comprehensive photochemistry model for exploration of the chemical composition of terrestrial exoplanet atmospheres. The photochemistry model is designed from the...

Detailed non-LTE (NLTE) calculations for red supergiant (RSG) stars are presented to investigate the influence of NLTE on the formation of atomic iron and titanium lines in the...

The first stars in the history of the Universe are likely to form in the dense central regions of {sim.to}10^5^-10^6^ M_{sun} cold dark matter halos at z{approx}10--50. The...

Semiempirical atmospheric models of solar surface features as observed at moderate resolution are useful tools for understanding the observed solar spectral irradiance...

Chemical analyses of late-type stars are usually carried out following the classical recipe: LTE line formation and homogeneous, plane-parallel, flux-constant, and LTE model...

Precise fundamental atmospheric stellar parameters and abundance determination of individual elements in stars are important for all stellar population studies. Non-local...

The ultraviolet-visible wavelength range holds critical spectral diagnostics for the chemistry and physics at work in planetary atmospheres. To date, time-series studies of...

We describe an application of the SEGUE Stellar Parameter Pipeline (SSPP) to medium-resolution stellar spectra obtained by the Large Sky Area Multi-Object Fiber Spectroscopic...

We have conducted spectrum analyses of 24 field metal-poor ([Fe/H]<-2) red horizontal-branch (RHB) stars identified in the HK objective-prism survey and 6 such stars in the...