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Modelling of stellar radiative intensities in various spectral pass-bands plays an important role in stellar physics. At the same time the direct calculations of the high-resolution spectrum and then integrating it over the given spectral…

Solar and Stellar Astrophysics · Physics 2021-06-30 L. S. Anusha , A. I. Shapiro , V. Witzke , M. Cernetic , S. K. Solanki , L. Gizon

Context. Realistic 3D time-dependent simulations of stellar near-surface convection employ the opacity binning method for efficient and accurate computation of the radiative energy exchange. The method provides several orders of magnitude…

Solar and Stellar Astrophysics · Physics 2023-07-19 A. Perdomo García , N. Vitas , E. Khomenko , M. Collados , C. Allende Prieto , I. Hubeny , Y. Osorio

Context. Stellar spectral synthesis is essential for various applications, ranging from determining stellar parameters to comprehensive stellar variability calculations. New observational resources as well as advanced stellar atmosphere…

Solar and Stellar Astrophysics · Physics 2021-09-15 V. Witzke , A. I. Shapiro , M. Cernetic , R. V. Tagirov , N. M. Kostogryz , L. S. Anusha , Y. C. Unruh , S. K. Solanki , R. L. Kurucz

We describe a new method for the computation of opacity distribution functions (ODFs) useful to calculate one-dimensional model atmospheres in local thermal equilibrium (LTE). The new method is fast enough to be applied on current…

Astrophysics · Physics 2007-05-23 F. Kupka , N. E. Piskunov

Distribution functions (DFs) for dynamically warm thin stellar disks residing in arbitrary axisymmetric potentials are presented which approximately reproduce pre-described surface-density and velocity-dispersion profiles. The functional…

Astrophysics · Physics 2009-10-31 Walter Dehnen

Aims. The derivation of spectroscopic parameters for M dwarf stars is very important in the fields of stellar and exoplanet characterization. The goal of this work is the creation of an automatic computational tool, able to derive quickly…

Solar and Stellar Astrophysics · Physics 2020-04-08 A. Antoniadis-Karnavas , S. G. Sousa , E. Delgado-Mena , N. C. Santos , G. D. C. Teixeira , V. Neves

Analytic distribution functions (DFs) for the Galactic disc are discussed. The DFs depend on action variables and their predictions for observable quantities are explored under the assumption that the motion perpendicular to the Galactic…

Astrophysics of Galaxies · Physics 2015-05-14 James Binney

(abridged) We develop a tool for the automated spectral classification of OB stars according to their sub-types. We use the regular Random Forest (RF) algorithm, the Probabilistic RF (PRF), and we introduce the KDE-RF method which is a…

Solar and Stellar Astrophysics · Physics 2022-01-12 E. Kyritsis , G. Maravelias , A. Zezas , P. Bonfini , K. Kovlakas , P. Reig

Spectral synthesis is a powerful tool with which to find the fundamental parameters of stars. Models are usually restricted to single values of temperature and gravity, and assume spherical symmetry. This approximation breaks down for…

Solar and Stellar Astrophysics · Physics 2024-06-27 Benjamin Montesinos

In accelerating and supersonic media, the interaction of photons with spectral lines can be of ultimate importance. However, fully accounting for such line forces currently can only be done by specialised codes in 1-D steady-state flows.…

Solar and Stellar Astrophysics · Physics 2022-11-16 L. G. Poniatowski , N. D. Kee , J. O. Sundqvist , F. A. Driessen , N. Moens , S. P. Owocki , K. G. Gayley , L. Decin , A. de Koter , H. Sana

Modeling the variability of the solar spectral irradiance is a key factor for understanding the solar influence on the climate of the Earth. As a first step to calculating the solar spectral irradiance variations we reproduce the solar…

Astrophysics · Physics 2009-11-13 M. Haberreiter , W. Schmutz , I. Hubeny

The spectral flux density of stars can indicate their atmospheric physical properties. A detector can obtain any band flux density at the design stage. However, the band flux density is confirmed and fixed in the process of operation…

Instrumentation and Methods for Astrophysics · Physics 2018-09-26 Chuanxin Zhang , Yuan Yuan , Zhaoyang Yu , Fuqiang Wang , Heping Tan

High-resolution spectrographs open a detailed window onto the atmospheres of stars and planets. As the number of systems observed with different instruments grows, it is crucial to develop a standard in analyzing spectral time series of…

Codes to compute mean opacities and radiative accelerations for arbitrary chemical mixtures using the Opacity Project recently revised data have been restructured in a client--server architecture and transcribed as a subroutine library.…

Optimal error estimation is key to achieve accurate photometry and astrometry. Stellar fluxes and positions in high angular resolution images are typically measured with PSF fitting routines, such as StarFinder. However, the formal…

Instrumentation and Methods for Astrophysics · Physics 2022-08-12 E. Gallego-Cano , R. Schödel , A. T. Gallego-Calvente , A. M. Ghez

High-quality stellar spectra are in great demand now - they are the most important ingredient in the stellar population synthesis to study galaxies and star clusters. Here we describe the procedures to increase the quality of flux…

Difference imaging is a technique for obtaining precise relative photometry of variable sources in crowded stellar fields and, as such, constitutes a crucial part of the data reduction pipeline in surveys for microlensing events or…

Astrophysics · Physics 2009-11-11 Holger Israel , Frederic V. Hessman , Sonja Schuh

By multiplexing information symbols in the delay-Doppler (DD) domain, orthogonal time frequency space (OTFS) is a promising candidate for future wireless communication in high-mobility scenarios. In addition to the superior communication…

Signal Processing · Electrical Eng. & Systems 2023-06-21 Kecheng Zhang , Zhongjie Li , Weijie Yuan , Yunlong Cai , Feifei Gao

Recently proposed orthogonal time frequency space (OTFS) modulation has been considered as a promising candidate for accommodating various emerging communication and sensing applications in high-mobility environments. In this paper, we…

Information Theory · Computer Science 2021-01-12 Shuangyang Li , Weijie Yuan , Zhiqiang Wei , Jinhong Yuan

Orbital-free density functional theory (OFDFT) offers a challenging way of electronic-structure calculations scaled as $\mathcal{O}(N)$ computation for system size $N$. We here develop a scheme of the OFDFT calculations based on the…

Computational Physics · Physics 2021-09-06 Fumihiro Imoto , Masatoshi Imada , Atsushi Oshiyama
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