A5042550506- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Astronomical and nuclear sciences
- Gamma-ray bursts and supernovae
- History and Developments in Astronomy
- Atmospheric and Environmental Gas Dynamics
- Calibration and Measurement Techniques
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- Historical Astronomy and Related Studies
- Spectroscopy and Laser Applications
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Geomagnetism and Paleomagnetism Studies
- Atomic and Molecular Physics
- Historical and Architectural Studies
- X-ray Diffraction in Crystallography
- Engineering Diagnostics and Reliability
- Space Science and Extraterrestrial Life
- Material Science and Thermodynamics
Vilnius University
2013-2024
Galaxies, Etoiles, Physique et Instrumentation
2011-2024
Centre National de la Recherche Scientifique
2011-2021
Observatoire de Paris
2021
Université Paris Sciences et Lettres
2021
Observatoire des Sciences de l’Univers Terre Homme Environnement Temps Astronomie
2017
Astronomical Observatory
2012
Université Paris Cité
2011
Délégation Paris 7
2011
Institute of Theoretical Physics
2009
The solar photospheric oxygen abundance is still widely debated. Adopting the chemical composition based on "low" abundance, as determined with use of three-dimensional (3D) hydrodynamical model atmospheres, results in a well-known mismatch between theoretical models and helioseismic measurements that so far unresolved. We carry out an independent redetermination by investigating center-to-limb variation OI IR triplet lines at 777 nm different sets spectra help detailed synthetic line...
Context. The cluster 47 Tuc is among the most metal-rich Galactic globular clusters and its metallicity similar to that of metal-poor disc stars open clusters. Like other clusters, it displays variations in abundances elements lighter than Si, which generally interpreted as evidence presence multiple stellar populations.
We present new synthetic broad-band photometric colors for late-type giants based on spectra calculated with the PHOENIX model atmosphere code. The grid covers effective temperatures K, gravities , and metallicities . show that individual are strongly affected by parameters such as molecular opacities, gravity, microturbulent velocity, stellar mass. Our exploratory 3D modeling of a prototypical giant shows convection has noticeable effect too, it alters significantly both vertical horizontal...
Aims. We utilize state-of-the-art three-dimensional (3D) hydrodynamical and classical 1D stellar model atmospheres to study the influence of convection on formation properties various atomic molecular spectral lines in four red giant stars, located close base branch, RGB (Teff ≈ 5000 K, log g = 2.5), characterized by different metallicities, [M/H] 0.0, −1.0, −2.0, −3.0.
Context. The MINCE (Measuring at Intermediate Metallicity Neutron-Capture Elements) project aims to provide high quality neutron-capture abundances measurements in several hundred stars intermediate metallicity,-2.5 < [Fe/H] -1.5. This will shed light on the origin of elements and chemical enrichment Milky Way. Aims. goal this work is chemically characterize second sample compare with galactic evolution model our disposal. Methods. We performed a standard abundance analysis based 1D LTE...
The Measuring at Intermediate Metallicity Neutron-Capture Elements (MINCE) project aims to provide high-quality neutron-capture abundances measurements for several hundred stars an intermediate metallicity of -2.5 < Fe/H $<-1.5$. This will shed light on the origin elements and chemical enrichment Milky Way. goal this work is chemically characterize second sample MINCE compare with galactic evolution model our disposal. We performed a standard abundance analysis based one-dimensional...
We investigate the character and role of convection in atmosphere a prototypical red giant located close to branch (RGB) tip with atmospheric parameters, Teff=3660K, log(g)=1.0, [M/H]=0.0. Differential analysis structures is performed using 3D hydrodynamical 1D classical models calculated CO5BOLD LHD codes, respectively. All share identical elemental composition, opacities equation-of-state. find that this particular consists two rather distinct regions: lower dominated by convective motions...
The European Gaia astrometry mission is due for launch in 2011. will rely on the proven principles of ESA's Hipparcos to create an all-sky survey about one billion stars throughout our Galaxy and beyond, by observing all objects down 20th magnitude. Through its massive measurement stellar distances, motions multi-colour photometry it provide fundamental data necessary unravelling structure, formation evolution Galaxy. This paper presents design performance broad- medium-band set photometric...
The atmospheres of cool stars are temporally and spatially inhomogeneous due to the effects convection.The influence this inhomogeneity, referred as granulation, on colours has never been investigated over a large range effective temperatures gravities. We aim study, in quantitative way, impact granulation colours. use CIFIST grid CO5BOLD hydrodynamical models compute emerging fluxes. These turn used theoretical UBVRI,2MASS,Hipparcos,Gaia SDSS systems. Every model corresponding one...
It is generally accepted today that Galactic globular clusters (GGCs) consist of at least two generations stars are different in their chemical composition and perhaps age. However, knowledge about the kinematical properties these stellar generations, which may provide important information for constraining evolutionary scenarios GGCs, still limited. We therefore study connections between cluster 47 Tuc. To achieve this goal, we used abundances Li, O, Na determined 101 main sequence turn-off...
Aims. We investigate the role of convection in formation atomic and molecular lines atmosphere a red giant star. For this purpose we study properties spectral that belong to number astrophysically important tracer elements, including neutral singly ionized atoms (Li i, N O Na Mg Al Si ii, S K Ca Ti Cr Mn Fe Co Ni Zn Sr Ba Eu ii), molecules (CH, CO, C2, NH, CN, OH).
Aims. Because of the complexities involved in treating spectral line formation full 3D and non-local thermodynamic equilibrium (NLTE), different simplified approaches are sometimes used to account for NLTE effects with hydrodynamical model atmospheres. In certain cases, chemical abundances derived 1D then corrected by adding 3D–1D LTE (Local Thermodynamic Equilibrium, LTE) abundance corrections (3D+NLTE approach). Alternatively, average ⟨3D⟩ atmospheres substitute models.
Context. Modeling the convection process is a long-standing problem in stellar physics. To date, all ad hoc models have relied on free parameter, α , (among others) that has no real physical justification and therefore poorly constrained. However, link exists between this parameter entropy of adiabat. There are existing prescriptions, derived from 3D atmospheric models, treat as function parameters (effective temperature, surface gravity, chemical composition). This can offer sufficient...
Context . Most of the studies on determination chemical composition metal-poor stars have been focused search most pristine stars, searching for imprints ejecta first supernovae. Apart from rare and very interesting r-enriched few elements are measurable in stars. On other hand, a lot work has done also thin-disc thick-disc abundance ratios metallicity range [Fe/H]> −1.5 dex to solar. In available literature, intermediate (−2.5<[Fe/H]< −1.5) frequently overlooked. The MINCE...
(Abridged) We investigate the effects of metallicity on broad-band photometric colors late-type giants, and make a comparison synthetic with observed properties giants over wide range effective temperatures (T_eff=3500-4800 K) gravities (log g=0.0-2.5), at [M/H]=-1.0 -2.0. The influence is generally small above \~3800 K, but grow larger lower T_eff, due to changing efficiency molecule formation which reduces molecular opacities [M/H]. To detailed late type in T_eff--color color--color...
Context. Although oxygen is an important tracer of Galactic chemical evolution, measurements its abundance in the atmospheres oldest stars are still scarce and rather imprecise. At lowest end metallicity scale, can only be measured giant most cases such rely on a single forbidden [O I] 630 nm line that very weak frequently blended with telluric lines. molecular OH lines located ultraviolet infrared could also used for diagnostics, abundances obtained from usually discrepant to level ~0.3-0.4...
Context. In recent years, Galactic archaeology has become a particularly vibrant field of astronomy, with its main focus set on the oldest stars our Galaxy. most cases, these have been identified as metal-poor. However, struggle to find ancient fossils produced an important bias in observations – particular, intermediate metal-poor (−2.5 < [Fe/H] −1.5) frequently overlooked. The missing information consequences for precise study chemical enrichment Galaxy, particular what concerns neutron...
Aims. Although observational data unequivocally point to the presence of chromospheres in red giant stars, no attempts have been made so far model them using 3D hydrodynamical atmospheres. We therefore compute an exploratory atmosphere for a cool order study dynamical and thermodynamic properties its chromosphere, as well influence chromosphere on observable properties.