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200 papers

We perform non-LTE calculations of lithium in late-type stars for a wide range of stellar parameters, including quantum mechanical cross-sections for collisions with neutral hydrogen and the negative hydrogen ion. Non-LTE abundance…

Solar and Stellar Astrophysics · Physics 2015-05-13 K. Lind , M. Asplund , P. S. Barklem

Aluminium plays a key role in studies of the chemical enrichment of the Galaxy and of globular clusters. However, strong deviations from LTE (non-LTE) are known to significantly affect the inferred abundances in giant and metal-poor stars.…

Solar and Stellar Astrophysics · Physics 2017-11-28 Thomas Nordlander , Karin Lind

Our ability to model the shapes and strengths of iron lines in the solar spectrum is a critical test of the accuracy of the solar iron abundance, which sets the absolute zero-point of all stellar metallicities. We use an extensive 463-level…

Solar and Stellar Astrophysics · Physics 2017-05-31 K. Lind , A. M. Amarsi , M. Asplund , P. S. Barklem , M. Bautista , M. Bergemann , R. Collet , D. Kiselman , J. Leenaarts , T. M. D. Pereira

In the current era of stellar spectroscopic surveys, synthetic spectral libraries are the basis for the derivation of stellar parameters and chemical abundances. In this paper, we compare the stellar parameters determined using five popular…

Instrumentation and Methods for Astrophysics · Physics 2020-09-03 Spencer Bialek , Sébastien Fabbro , Kim A. Venn , Nripesh Kumar , Teaghan O'Briain , Kwang Moo Yi

The last decade showed an impressive observational effort from the photometric and spectroscopic point of view for ancient stellar clusters in our Galaxy and beyond. The theoretical interpretation of these new observational results requires…

Solar and Stellar Astrophysics · Physics 2013-06-06 M. Dell'Omodarme , G. Valle , S. Degl'Innocenti , P. G. Prada Moroni

With the goal of producing a reliable set of model atoms and singly-ionized ions for use in building NLTE model atmospheres, we have combined measured energy levels, critically-compiled line transition probabilities, and resonance-averaged…

Astrophysics · Physics 2009-11-07 C. Allende Prieto , D. L. Lambert , I. Hubeny , T. Lanz

We present a library of 1654 high-resolution stellar spectra, with a sampling of 0.3 A and covering the wavelength range from 3000 A ~ to 7000 A The library was computed with the latest improvements in stellar atmospheres, incorporating…

The precise analysis of properties of planetary nebulae is strongly dependent on good models for the stellar ionizing spectrum. Observations in the UV - X-ray wavelength range as well as NLTE model atmosphere calculations of spectra of…

Astrophysics · Physics 2009-11-07 Thomas Rauch

Spectra for 2D stars in the 1.5D approximation are created from synthetic spectra of 1D non-local thermodynamic equilibrium (NLTE) spherical model atmospheres produced by the PHOENIX code. The 1.5D stars have the spatially averaged…

Solar and Stellar Astrophysics · Physics 2014-05-07 Mitchell E. Young , C. Ian Short

Theoretical atmosphere models provide the basis for a variety of applications in astronomy. In simplified one-dimensional (1D) atmosphere models, convection is usually treated with the mixing length theory despite its well-known…

Solar and Stellar Astrophysics · Physics 2015-06-17 Zazralt Magic , Remo Collet , Martin Asplund

We used moderately high-resolution, high S/N spectra to study the chemical composition of 10 field ab-type RR Lyrae stars. A new temperature scale was determined from literature Infrared Flux Method measures of subdwarfs and the Kurucz…

Astrophysics · Physics 2009-11-24 G. Clementini , E. Carretta , R. Gratton , R. Merighi , J. R. Mould , J. K. McCarthy

We compute the emergent stellar spectra from the UV to far infrared for different viewing angles using realistic 3D model atmospheres for a large range in stellar parameters to predict the stellar limb darkening. We have computed full 3D…

Solar and Stellar Astrophysics · Physics 2014-12-24 Zazralt Magic , Andrea Chiavassa , Remo Collet , Martin Asplund

We present a grid of spherically symmetric model atmospheres for young pre-MS stars. This grid spans the parameter range $2000\K \leq \Teff \leq 6800\K$ and $2.0 \leq \logg \leq 3.5$ for $M=0.1\Msun$, appropriate for low mass stars and…

Astrophysics · Physics 2010-04-29 France Allard , Peter H. Hauschildt , Andreas Schweitzer

We present the results of a set of model atmospheres and synthetic spectra computed with the PHOENIX code. The models cover a range of effective temperatures 2700 K <= T_eff <= 10 000 K, gravities (-0.5 <= log(g)<= 5.5) and metalicities…

Astrophysics · Physics 2007-05-23 I. Brott , P. H. Hauschildt

We present work on H alpha spectral line characteristics in PHOENIX stellar model atmospheres and their comparison to microlensing observations. We examine in detail the H alpha equivalent width (EW) and the line shape characteristics for…

Astrophysics · Physics 2009-11-11 Christine Thurl , Penny D. Sackett , Peter H. Hauschildt

Grids of stellar models are useful tools to derive the properties of stellar clusters, in particular young clusters hosting massive stars, and to provide information on the star formation process in various mass ranges. Because of their…

Solar and Stellar Astrophysics · Physics 2019-05-01 L. Haemmerlé , P. Eggenberger , S. Ekström , C. Georgy , G. Meynet , A. Postel , M. Audard , M. Sørensen , T. Fragos

We present new detailed NLTE calculations for model atmospheres of novae during outburst. This fully self-consistent NLTE treatment for a number of model atoms includes 3922 NLTE levels and 47061 NLTE primary transitions. We discuss the…

Astrophysics · Physics 2009-10-30 Peter H. Hauschildt , Steven N. Shore , Greg J. Schwarz , E. Baron , S. Starrfield

We present the first models allowing one to explore in a consistent way the influence of changes in the alpha-element-to-iron abundance ratio on the high-resolution spectral properties of evolving stellar populations. The models cover the…

Astrophysics · Physics 2008-01-08 P. Coelho , G. Bruzual , S. Charlot , A. Weiss , B. Barbuy , J. Ferguson

Context. The modeling of stellar spectra of flux standards observed by the Hubble and James Webb space telescopes requires a large synthetic spectral library that covers a wide atmospheric parameter range. Aims. The aim of this paper is to…

A new model grid containing 228,016 synthetic red supergiant explosions (Type II supernovae) is introduced. Time evolution of spectral energy distributions from 1 A to 50,000 A (100 frequency bins in a log scale) is computed at each time…

High Energy Astrophysical Phenomena · Physics 2023-05-03 Takashi J. Moriya , Bhagya M. Subrayan , Dan Milisavljevic , Sergei I. Blinnikov