A5088086323- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Scientific Research and Discoveries
- Historical Astronomy and Related Studies
- Astronomical and nuclear sciences
- Pulsars and Gravitational Waves Research
- Inertial Sensor and Navigation
- Diverse Industrial Engineering Technologies
- Maritime Transport Emissions and Efficiency
- Industrial Engineering and Technologies
- Veterinary Practice and Education Studies
- Calibration and Measurement Techniques
- Electric Power Systems and Control
- Particle Accelerators and Free-Electron Lasers
- Advanced Scientific Techniques and Applications
- Biological Activity of Diterpenoids and Biflavonoids
Institute of Astronomy and National Astronomical Observatory
2010-2023
University of Mining and Geology "Saint Ivan Rilski"
2021-2023
Fuzzy Systems Institute
2021
Bulgarian Academy of Sciences
1986-2020
Nikola Vaptsarov Naval Academy
2020
University of South Africa
2017
State of The Art
2014
Zimmer Biomet (Netherlands)
2014
Central Laboratory of Solar Energy and New Energy Sources
2007
Astronomical Observatory
2004-2005
In this paper, we present high- and middle-resolution spectral observations of seven heartbeat (HB), highly eccentric, Kepler binaries: four them (KIC 3230227, KIC 03547874, 03749404, 07672068) are SB2 stars the remaining three 04949194, 05960989, 10092506) SB1 stars. The flux amplitudes their HB signals from 0.001 to 0.01. Five targets sample with eccentricity above 0.64 show tidally induced oscillations, which harmonics orbital period. global parameters all were determined as a result...
Context. Light and spectrum variations of the magnetic chemically peculiar (mCP) stars are explained by oblique rigid rotator model with a rotation period usually assumed to be stable on long time scale. A few exceptions, such as CU Vir or 56 Ari, have been reported displaying an increase in their period. possible light has also suggested from observations helium-strong mCP star HD 37776 (V901 Ori).
Aims. We investigate the magnetic dichotomy between Ap/Bp and other A-type stars by carrying out a deep spectropolarimetric study of Am HgMn stars.
The λ Bootis stars are Population I, late B- to early F-type stars, with moderate extreme (up a factor 100) surface underabundances of most Fe-peak elements and solar abundances lighter (C, N, O S). To put constraints on the various existing theories that try explain these peculiar we investigate observational properties compared reference sample normal stars. Using photometric systems Hipparcos data, analyse validity standard calibrations, elemental abundances, Galactic space motions.
Aims.We have studied the active giant V390 Aur using spectropolarimetry to obtain direct and simultaneous measurements of magnetic field activity indicators in order infer origin activity.
After establishing the synthetic Δa photometric system in first paper of this series, we now present model atmospheres computed with individual abundances for a representative sample chemically peculiar (CP) stars and either confirm or redetermine their input parameters through comparisons photometric, spectrophotometric high-resolution spectroscopic data. The final models obtained from procedure were used to compute indices which compared observations. observed behaviour is reproduced...
One of the main characteristics proclaimed for group λ Bootis stars is apparent solar abundance light elements C, N, O and S. The typical pattern completed by strong underabundances Fe-peak elements. In first paper this series, we have shown that carbon less abundant than oxygen but both are still significantly more mean abundances, based on a detailed non-LTE investigation, were found -0.37 dex -0.07 dex, respectively. As further step, now present abundances nitrogen sulphur thirteen...
Two observational campaigns were carried out during the eclipses of EE Cep in 2003 and 2008/9 to verify whether eclipsing body system is indeed a dark disk understand observed changes depth durations eclipses. Multicolour photometric data spectroscopic observations at both low high resolution collected. We numerically modelled variations brightness colour tested models with different structure. considered possibility precession. The complete set collected last three are made available...
Context.We continue our survey of magnetic chemically peculiar (CP2) stars in galactic open clusters to shed more light on their origin and evolution.
In a sample of six young open clusters (NGC 1502, NGC 3105, Stock 16, 6268, 7235, and 7510) we investigated 1753 objects using the narrow band, three filter photometric system resulting in detection eleven bona-fide magnetic chemically peculiar (CP) stars five Be or metal-weak stars. The results for distant cluster 3105 is most important because still unknown influence global metallicity gradient Milky Way. These findings confirm that CP are present very ages (log t ≥ 6.90) at galactocentric...
Aims.The detection of magnetic chemically peculiar (CP2) stars in open clusters the Milky Way can be used to study influence different galactic environments on (non-)presence peculiarities, which has taken into account stellar evolution models. Furthermore it is still unknown if CP2 phenomenon evolves, i.e. does strength peculiarity feature at 5200 Å increase or decrease with age.
We present results of a multi-site photometric campaign on the high-amplitude $δ$\,Scuti star KIC\,6382916 in {\it Kepler} field. The was observed over 85-d interval at five different sites North America and Europe during 2011. photometry ground-based multicolour light curves are used to investigate pulsational content identify principal modes. High-dispersion spectroscopy also obtained order derive stellar parameters projected rotational velocity. From an analysis time series, three...
Abstract The small group of λ Bootis stars comprises late B to early F-type stars, with moderate extreme (up a factor 100) surface under-abundances most Fe-peak elements and solar abundances lighter (C, N, O, S). main mechanisms responsible for this phenomenon are atmospheric diffusion, meridional mixing, accretion material from their surroundings. Especially spectroscopic binary (SB) systems Bootis-type components very important investigate the evolutionary status process in more details....
We present high-resolution spectroscopic observations of the two λ Bootis type binary systems HD 84948 and 171948. Both consist true stars, as has already been proven by a detailed abundance analysis taking into account nature. Nevertheless, we have obtained non-LTE abundances for carbon oxygen in order to investigate those important elements. The fit excellently typical pattern this group, leaving no doubt that all four components are stars. With help derived orbital elements it is possible...
EE Cep is an eclipsing binary with a period of 5.6 years. The next eclipse will occur soon, in May–June 2003, and all available past eclipses were collected briefly analysed. shows very large changes the shape depth minima during different eclipses, however it possible to single out some persistent features. analysis suggests that body should be long object surrounded by extended semi-transparent envelope. As explanation, model precessing optically thick disc, inclined plane orbit, invoked....
The lambda Bootis (LB) stars are located at the upper main sequence of H-R diagram and exhibit a peculiar abundance pattern. light elements (C, N, O, S) present solar abundances whereas all other moderately to strongly underabundant. It has not yet been determined whether that pattern is intrinsic, or restricted stellar surface. If we follow hypothesis LB intrinsically metal-weak, then there should be connection with intermediate Population II F-weak objects. Such possible affinity...
We continue here the systematic abundance analysis of a sample Am binaries in order to search for possible anomalies driven by tidal interaction these binary systems.
We report on a multi-site photometric campaign the high-amplitude $\delta$ Scuti star V2367 Cyg in order to determine pulsation modes. also used high-dispersion spectroscopy estimate stellar parameters and projected rotational velocity. Time series multicolour photometry was obtained during 98-d interval from five different sites. These data were together with model atmospheres non-adiabatic models identify spherical harmonic degree of three independent frequencies highest amplitude as well...
The main goal of this paper is to continue a systematic abundance analysis sample Am binaries in order search for possible anomalies driven by tidal interaction these binary systems.