A5041552733- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- History and Developments in Astronomy
- Spectroscopy and Laser Applications
- Astrophysics and Star Formation Studies
- Atmospheric Ozone and Climate
- Calibration and Measurement Techniques
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Advanced Optical Sensing Technologies
- CCD and CMOS Imaging Sensors
- Geophysics and Gravity Measurements
- Spectroscopy Techniques in Biomedical and Chemical Research
- Neutrino Physics Research
- Geomagnetism and Paleomagnetism Studies
- Pulsars and Gravitational Waves Research
- Atomic and Subatomic Physics Research
- Advanced Measurement and Metrology Techniques
- Advanced Fiber Optic Sensors
Lund University
2012-2024
TU Dortmund University
2023
University of Łódź
2023
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2023
University of Turku
2023
Niels Brock
2023
University of Copenhagen
2023
Main Astronomical Observatory
2023
Taras Shevchenko National University of Kyiv
2023
National Academy of Sciences of Ukraine
2023
Photospheric Spectrum Line Asymmetries and Wavelength Shifts, Page 1 of < Previous page | Next > /docserver/preview/fulltext/astro/20/1/annurev.aa.20.090182.000425-1.gif
With its unprecedented light-collecting area for night-sky observations, the Cherenkov Telescope Array (CTA) holds great potential also optical stellar astronomy, in particular as a multi-element intensity interferometer realizing imaging with sub-milliarcsecond angular resolution. Such an order-of-magnitude increase of spatial resolution achieved astronomy will reveal surfaces rotationally flattened stars structures their circumstellar disks and winds, or gas flows between close binaries....
Accuracy levels of metres per second require the fundamental concept "radial velocity" for stars and other distant objects to be examined, both as a physical velocity, measured by spectroscopic astrometric techniques. Already in classical (non-relativistic) framework line-of-sight velocity component is an ambiguous concept, depending on whether, e.g., time light emission (at object) or that detection (by observer) used recording coordinate. Relativistic effects measurements made inside...
Stellar intensity scintillation in the optical was extensively studied at astronomical observatory on La Palma (Canary Islands). Atmospheric turbulence causes "flying shadows" ground, and fluctuations occur both because this pattern is carried by winds intrinsically changing. Temporal statistics time changes were treated Paper I, dependence wavelength II. This paper discusses structure of these flying shadows analyzes signals recorded telescopes different size with (secondary‐mirror)...
Stellar intensity scintillation in the optical was extensively studies at astronomical observatory on La Palma (Canary Islands). Photon-counting detectors and digital signal processors recorded temporal auto-and cross-correlation functions, power spectra, probability distributions. This first paper of a series treats properties scintillation, ranging from microseconds to seasons year. Previous studies, mechanisms producing are reviewed. Atmospheric turbulence causes 'flying shadows' ground,...
Radial motions of stars in nearby moving clusters are determined from accurate proper and trigonometric parallaxes, without any use spectroscopy. Assuming that cluster members share the same velocity vector (apart a random dispersion), we apply maximum-likelihood method on astrometric data Hipparcos to compute radial space velocities (and their dispersions) Ursa Major, Hyades, Coma Berenices, Pleiades, Praesepe clusters, for Scorpius-Centaurus, α Persei, “HIP 98321” associations. The motion...
Building on the experience of high-resolution community with suite VLT spectrographs, which has been tremendously successful, we outline here (science) case for a high-fidelity, spectrograph wide wavelength coverage at E-ELT. Flagship science drivers include: study exo-planetary atmospheres prospect detection signatures life rocky planets; chemical composition planetary debris surface white dwarfs; spectroscopic protoplanetary and proto-stellar disks; extension Galactic archaeology to Local...
Abstract Highest resolution imaging in astronomy is achieved by interferometry, connecting telescopes over increasingly longer distances and at successively shorter wavelengths. Here, we present the first diffraction-limited images visual light, produced an array of independent optical telescopes, connected electronically only, with no links between them. With small second-order coherence sources measured through intensity interferometry 180 baselines pairs two-dimensional reconstructed. The...
Atmospheric intensity scintillation of stars on milli- and microsecond time scales was extensively measured at the astronomical observatory La Palma (Canary Island). Scintillation statistics temporal changes were discussed in Paper I, while this paper shows how depends optical wavelength. Such effects originate from changing refractive index air, wavelength-dependent diffraction atmospheric inhomogeneities. The variance σ2/I increases for shorter wavelengths, small zenith distances...
Context. Spectral-line asymmetries (displayed as bisectors) and wavelength shifts are signatures of the hydrodynamics in solar stellar atmospheres. Theory may precisely predict idealized lines, but accuracies real observed spectra limited by blends, few suitable imprecise laboratory wavelengths, instrumental imperfections.
CONTEXT: High-precision stellar analyses require hydrodynamic modeling to interpret chemical abundances or oscillation modes. Exoplanet atmosphere studies background spectra be known along the transit path while detection of Earth analogs microvariability understood. Hydrodynamic 3-D models can computed for widely different stars but have been tested in detail only Sun with its resolved surface features. Model predictions include spectral line shapes, asymmetries, and wavelength shifts,...
Gravitational redshifts in solar-type main-sequence stars are expected to be some 500 ms$^{-1}$ greater than those giants. Such a signature is searched for between groups of open-cluster which share the same average space motion and thus have Doppler shift. 144 cool giants were observed M67 open cluster using ESO FEROS spectrograph, obtaining radial velocities by cross correlation with spectral template. dwarf giant radial-velocity distributions well represented Gaussian functions, sharing...
Experiments are in progress to prepare for intensity interferometry with arrays of air Cherenkov telescopes. At the Bonneville Seabase site, near Salt Lake City, a testbed observatory has been set up two 3-m telescopes on 23-m baseline. Cameras being constructed, control electronics either off- or online analysis data. Lund Observatory (Sweden), Technion (Israel) and at University Utah (USA), laboratory interferometers simulating stellar observations have experiments progress, using various...
A long-held vision has been to realize diffraction-limited optical aperture synthesis over kilometer baselines. This will enable imaging of stellar surfaces and their environments, reveal interacting gas flows in binary systems. An opportunity is now opening up with the large telescope arrays primarily erected for measuring Cherenkov light air induced by gamma rays. With suitable software, such telescopes could be electronically connected also used intensity interferometry. Second-order...
Testing 3D hydrodynamic models of stellar atmospheres is feasible by retrieving spectral line shapes across disks, using differential spectroscopy during exoplanet transits. From synthetic data at hyper-high resolution, characteristic patterns for FeI and FeII lines were identified in Paper IV from spanning T=3964-6726K (spectral types approx. K8V-F3V). The observability among different strength, excitation potential ionization level are now examined, as observed ordinary resolutions the...
Context. The search for small exoplanets around solar-type stars is limited by stellar physical variability, such as a jittering in the apparent photospheric radial velocity. While chromospheric variability has been aptly studied, challenges remain observation, modeling. and understanding much smaller fluctuations spectral line strengths, shapes, shifts. Aims. Extreme-precision radial-velocity spectrometers allow highly precise spectroscopy time series of Sun (seen star) enable monitoring...