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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…

Solar and Stellar Astrophysics · Physics 2025-03-18 S. A. Korotin , K. O. Kiselev

Rapidly growing datasets from stellar spectroscopic surveys are providing unprecedented opportunities to analyse the chemical evolution history of our Galaxy. However, spectral analysis requires accurate modelling of synthetic stellar…

Solar and Stellar Astrophysics · Physics 2024-03-29 J. W. E. Mallinson , K. Lind , A. M. Amarsi , K. Youakim

Diagnostic diagrams of forbidden lines have been a useful tool for observers in astrophysics for many decades now. They are used to obtain information on the basic physical properties of thin gaseous nebulae. Some diagnostic diagrams are in…

Instrumentation and Methods for Astrophysics · Physics 2015-06-18 Bastian Proxauf , Silvia Oettl , Stefan Kimeswenger

We present a grid of optical (3200--7200 \AA) synthetic spectra calculated with Tlusty/Synspec. The new NLTE model atmospheres include the most recent hydrogen Stark broadening profiles; were calculated in opacity sampling and limited to…

Solar and Stellar Astrophysics · Physics 2013-08-02 Peter Nemeth , Roy Østensen , Pier-Emmanuel Tremblay , Ivan Hubeny

We present new high angular resolution near-infrared spectroscopic observations of the nuclear star cluster surrounding the Milky Way's central supermassive black hole. Using the integral-field spectrograph OSIRIS on Keck II behind the…

Solar and Stellar Astrophysics · Physics 2015-06-12 Tuan Do , Jessica R. Lu , Andrea M. Ghez , Mark R. Morris , Sylvana Yelda , Gregory D. Martinez , Shelley A. Wright , Keith Matthews

Far infrared cooling lines are ubiquitous features in the spectra of star forming galaxies. Surveys of redshifted fine-structure lines provide a promising new tool to study structure formation and galactic evolution at redshifts including…

Astrophysics of Galaxies · Physics 2015-05-05 A. Kogut , E. Dwek , S. H. Moseley

Metal-polluted white dwarfs (DZ stars) are characterized by a helium-rich atmosphere contaminated by heavy elements traces originating from accreted rocky planetesimals. As a detailed spectroscopic analysis of those objects can reveal the…

Solar and Stellar Astrophysics · Physics 2019-05-01 S. Blouin , N. F. Allard , T. Leininger , F. X. Gadéa , P. Dufour

The 21-cm brightness-temperature field of neutral hydrogen during the Epoch of Reionization and Cosmic Dawn is a rich source of cosmological and astrophysical information, primarily due to its significant non-Gaussian features. However, the…

Cosmology and Nongalactic Astrophysics · Physics 2024-09-12 Bohdan Bidenko , Léon V. E. Koopmans , P. Daniel Meerburg

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…

Solar and Stellar Astrophysics · Physics 2018-03-14 A. Chiavassa , L. Casagrande , R. Collet , Z. Magic , L. Bigot , F. Thevenin , M. Asplund

The sn stars present sharp Balmer lines, sharp metallic lines and broad coreless He I lines. Initially Abt & Levato proposed a shell-like nature to explain the sn stars, although this scenario was subsequently questioned. We aim to derive…

Solar and Stellar Astrophysics · Physics 2014-01-23 C. Saffe , H. Levato

We present a new detailed model of the He I collisional-recombination spectrum based on the most up-to-date atomic data. The model accounts for radiative transfer effects and the influence of a non-zero optical depth in He I lines arising…

Astrophysics of Galaxies · Physics 2026-01-21 Oleg Kurichin , Alexandre Ivanchik

Leveraging the large sample size of low-resolution spectroscopic surveys to constrain white dwarf stellar structure requires an accurate understanding of the shapes of hydrogen absorption lines, which are pressure broadened by the Stark…

In the present paper we propose to update the standard calculation of Stark line profiles for autoionizing atomic states in dense plasmas, i.e. warm dense matter and strongly coupled plasmas. This is motivated by the importance of taking…

Plasma Physics · Physics 2017-02-10 Y. J. Aouad

We report on our new calculations of unified line profiles of K perturbed by He using ab initio potential data for the conditions prevailing in cool substellar brown dwarfs and hot dense planetary atmospheres with temperatures from…

Solar and Stellar Astrophysics · Physics 2024-03-06 N. F. Allard , J. F. Kielkopf , K. Myneni , J. N. Blakely

Determining accurate effective temperatures of stars buried in the dust-obscured Galactic regions is extremely difficult from photometry. Fortunately, high-resolution infrared spectroscopy is a powerful tool for determining the temperatures…

Supersonic helium beams are used in a wide range of applications, for example surface scattering experiments and, most recently, microscopy. The high ionization potential of neutral helium atoms makes it difficult to build efficient…

Atomic and Molecular Clusters · Physics 2018-12-12 Adrià Salvador Palau , Sabrina D. Eder , Truls Andersen , Anders Komar Ravn , Gianangelo Bracco , Bodil Holst

About 70-80% of stars in our solar and galactic neighborhood are M dwarfs. They span a range of low masses and temperatures relative to solar-type stars, facilitating molecule formation throughout their atmospheres. Standard stellar…

Solar and Stellar Astrophysics · Physics 2023-02-22 Aishwarya R. Iyer , Michael R. Line , Philip S. Muirhead , Jonathan J. Fortney , Ehsan Gharib-Nezhad

We use extensive gravity-sensitive DDO 51 photometry over 5100 square degrees, combined with SDSS broadband photometry, to select a catalog of $\sim 4,000$ giant stars covering a large fraction of the high Galactic latitude sky and reaching…

Astrophysics of Galaxies · Physics 2016-12-14 Colin T. Slater , David L. Nidever , Jeffrey A. Munn , Eric F. Bell , Steven R. Majewski

We present describe a new computer code that solves the radiative transfer problem on multi-resolution grids. If the cloud model is from an MHD simulation on a regular cartesian grid, criteria based for example on local density or velocity…

Astrophysics · Physics 2009-11-10 M. Juvela , P. Padoan

White dwarf asteroseismology offers the opportunity to probe the structure and composition of stellar objects governed by relatively simple physical principles. The observational requirements of asteroseismology have been addressed by the…

Astrophysics · Physics 2009-11-06 Travis S. Metcalfe
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