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Modeling the atmospheres of exoplanets is fundamental to understanding their atmospheric physics and chemical processes. While one-dimensional (1D) atmospheric models with 1D radiative transfer (RT) have been widely used, advances in…

Earth and Planetary Astrophysics · Physics 2025-12-01 Rahul Arora , Liton Majumdar

Hot molecular cores (HMCs) are intermediate stages of high-mass star formation and are also known for their rich emission line spectra at (sub-)mm wavebands. The observed spectral feature of HMCs such as total number of emission lines and…

We compute model atmospheres and emergent spectra for low field (B<10^10 G) neutron stars, using new opacity and equation of state data from the OPAL project. These computations, incorporating improved treatments of flux transport and…

Astrophysics · Physics 2009-10-28 Mohan Rajagopal , Roger Romani

Recent observations of the HDO/H$_2$O ratio toward protostars in isolated and clustered environments show an apparent dichotomy, where isolated sources show higher D/H ratios than clustered counterparts. Establishing which physical and…

Astrophysics of Galaxies · Physics 2021-05-12 S. S. Jensen , J. K. Jørgensen , K. Furuya , T. Haugbølle , Y. Aikawa

The solar oxygen abundance has undergone a major downward revision in the last decade, the most noticeable one being the update including 3D hydrodynamical simulations to model the solar photosphere. Up to now, such an analysis has been…

Context: The stable element hafnium (Hf) and the radioactive element thorium (Th) were recently suggested as a suitable pair for radioactive dating of stars. The applicability of this elemental pair needs to be established for stellar…

Astrophysics · Physics 2009-11-13 Elisabetta Caffau , L. Sbordone , H. -G. Ludwig , P. Bonifacio , M. Steffen , N. T. Behara

The topic of the present study is combining a dynamic model of a protoplanetary disk with the computations of radiation transfer for obtaining synthetic spectra and disk images suitable for immediate comparison of the model with…

Earth and Planetary Astrophysics · Physics 2021-04-23 A. M. Skliarevskii , Ya. N. Pavlyuchenkov , E. I. Vorobyov

Modelling long-time convective flows in the interiors of stars is extremely challenging using conventional compressible hydrodynamics codes due to the acoustic timestep limitation. Many of these flows are in the low Mach number regime,…

Computational Physics · Physics 2020-12-09 A. Harpole , D. Fan , M. P. Katz , A. J. Nonaka , D. E. Willcox , M. Zingale

The chromosphere in internetwork regions of the quiet Sun was regarded as a static and homogeneous layer for a long time. Thanks to advances in observations and numerical modelling, the wave nature of these atmospheric regions received…

Astrophysics · Physics 2015-06-24 Sven Wedemeyer-Böhm

Pre-stellar cores represent the earliest stage of the star- and planet-formation process. By characterizing the physical and chemical structure of these cores we can establish the initial conditions for star and planet formation and…

Astrophysics of Galaxies · Physics 2023-07-05 S. S. Jensen , S. Spezzano , P. Caselli , T. Grassi , T. Haugbølle

The atmospheres of massive O-type stars (O stars) are dynamic, turbulent environments resulting from radiatively driven instabilities over the iron bump, located slightly beneath the stellar surface. Here, complex radiation hydrodynamic…

We construct a 3D radiative-hydrodynamic model atmosphere of parameters Teff = 4820 K, log g = 4.5, and solar chemical composition. The theoretical line profiles computed with this model are asymmetric, with their bisectors having a…

Solar and Stellar Astrophysics · Physics 2015-05-13 I. Ramirez , C. Allende Prieto , L. Koesterke , D. L. Lambert , M. Asplund

We analyze a three-dimensional smoothed particle hydrodynamics simulation of an evolving and later collapsing pre-stellar core. Using a three-dimensional continuum radiative transfer program, we generate images at 7 micron, 15 micron, 175…

Astrophysics · Physics 2009-11-10 J. Steinacker , B. Lang , A. Burkert , A. Bacmann , Th. Henning

CHROMIS, a new imaging spectrometer at the Swedish 1-m Solar Telescope (SST), can observe the chromosphere in the H and K lines of Ca II at high spatial and spectral resolution. Accurate modeling as well as an understanding of the formation…

We present the results of a three-dimensional, relativistic, hydrodynamic simulation of a precessing jet into which a compact blob of matter is injected. A comparison of synthetic radio maps computed from the hydrodynamic model, taking into…

Spectral synthesis calculations based on three-dimensional stellar atmosphere models are limited by the affordable angular resolution of the radiation field. This hampers an accurate treatment of rotational line broadening. We aim to find a…

Astrophysics · Physics 2007-07-24 Hans-G. Ludwig

We present an overview of the current status of our efforts to derive the microturbulence and macroturbulence parameters (ximic and ximac) from the CIFIST grid of CO5BOLD 3D model atmospheres as a function of the basic stellar parameters…

Solar and Stellar Astrophysics · Physics 2013-06-19 M. Steffen , E. Caffau , H. -G. Ludwig

Here we formulate and solve the 3D radiative transfer problem of the polarization of the solar continuous radiation. Our approach takes into account not only the anisotropy of the continuum radiation, but also the symmetry-breaking effects…

Astrophysics · Physics 2011-02-11 J. Trujillo Bueno , N. Shchukina

We present the results of a series of calculations studying the collapse of molecular cloud cores performed using a three-dimensional smoothed particle hydr odynamics code with radiative transfer in the flux-limited diffusion approximation.…

Astrophysics · Physics 2009-11-13 Stuart C. Whitehouse , Matthew R. Bate

Lyman $\alpha$ observations of the transiting exoplanet HD 209458b enable the study of exoplanets exospheres exposed to stellar EUV fluxes, as well as the interacting stellar wind properties. In this study we present 3D hydrodynamical…

Earth and Planetary Astrophysics · Physics 2019-07-17 A. Esquivel , M. Schneiter , C. Villarreal D'Angelo , M. A. Sgró , L. Krapp