A5039425988- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Neutrino Physics Research
- Calibration and Measurement Techniques
- History and Developments in Astronomy
- Scientific Research and Discoveries
- Advanced X-ray Imaging Techniques
- Dark Matter and Cosmic Phenomena
- Enzyme Structure and Function
- Coding theory and cryptography
- Heart Rate Variability and Autonomic Control
- Particle accelerators and beam dynamics
- Spacecraft and Cryogenic Technologies
- Algorithms and Data Compression
- High-pressure geophysics and materials
- Nuclear physics research studies
- Seismic Waves and Analysis
- Advanced Frequency and Time Standards
University of Patras
2013-2024
Hellenic Open University
2012
University of Manchester
1992
We present the identification and photometric analysis of 30 new low mass ratio (LMR) totally eclipsing contact binaries found in Catalina Sky Survey data. The LMR candidates are identified using Fourier coefficients visual inspection. perform a detailed scan parameter plane mass-ratio (q) versus inclination (i) Phoebe-0.31 scripter to derive best (q,i) pair for initial models. relative physical parameters determined from final model each system. A Monte-Carlo approach was adopted errors....
We present a new observational campaign, DWARF, aimed at detection of circumbinary extrasolar planets using the timing minima low-mass eclipsing binaries. The observations will be performed within an extensive network relatively small to medium-size telescopes with apertures ~20-200 cm. starting sample objects monitored contains (i) binaries M and K components, (ii) short-period sdB or sdO component, (iii) post-common-envelope systems containing WD, which enable determine high precision....
New CCD photometric BVRI observations of the puzzling W UMa type binary star, TZ Bootis, are presented from our in 2010. By using updated version Wilson–Devinney code, first modern solution is deduced new and published spectroscopic data. This low mass ratio turns out to be a deep overcontact system with f = 52% A-subtype. A spot model has been applied fit particular features light curves. Based on seven minimum times all others compiled literature over 70 yr, we studied orbital period O–C...
New observations using narrow band imaging, long-slit spectroscopy and MERLIN of the nuclear region Seyfert galaxy NGC~4051 have been made. An edge brightened, triangular ionized gas extending 420 pc from centre has detected. Long-slit spectra this ionised gas, taken at 1.5\arcsec\ core, show \oiii\ emission line to consist two velocity components, both blue-shifted systemic radial velocity, with widths 140\kms\ separated by 120\kms. This is co-spatial weak extended radio suggestive a...
We present a detailed analysis of the interesting W UMa binary FI Boo in view spectroscopic signature third body through photometry, period variation, and thorough investigation solution uniqueness. obtained new BVRcIc photometric data that, when combined with data, enable us to analyze system determine its basic orbital physical properties PHOEBE, as well variation by studying times minima. This approach allows study long-term changes for first time order investigate presence check...
Abstract Asymmetries between the two maxima of light curves contact binaries, known as O'Connell effect, have been identified using All Sky Automated Survey, All-Sky Survey for Supernovae, Northern Variability Optical Gravitational Lensing Experiment, and Monitoring Camera sky surveys. The morphology mean curve has analyzed a total 43,659 objects already classified binaries. After applying several filters criteria, we present sample 797 systems representing largest to date asymmetries...
We present an updated catalog of 4680 northern eclipsing binaries (EBs) with Algol-type light-curve (LC) morphology (i.e., well-defined beginnings and ends primary secondary eclipses), using data from the Catalina Sky Surveys. Our work includes revised period determinations, phenomenological parameters LCs, system classifications based on machine-learning techniques. While most new periods are in excellent agreement those provided original catalogs, improved values now available for ∼10%...
Deep optical CCD images of the supernova remnant G 32.8-0.1 were obtained where filamentary and diffuse emission was discovered. The acquired in lines H<i>α<i/>+[ N ii] [S ii]. Filamentary structures are detected most areas remnant, while no significant [O iii] is present. flux-calibrated suggest that originates from shock-heated gas since ii]/H<i>α<i/> ratio greater than 1.2. Spitzer at 8 <i>μ<i/>m 24 show a few to be correlated with filaments, radio 1.4 GHz same area found very well...
New CCD four-color light curves of TY Boo made on eight nights over 2010–2011 were analyzed in comparison with historical obtained from 1969 through 2011. The could all be represented by a unique geometry and wavelength consistent phototometric parameters two-spot model either stellar component. It is confirmed that shallow W-type contact binary system degree factor f = 7.6% (±0.8). A period investigation based available data shows long-term decrease (dP/dt −3.65 × 10−8 days yr−1) an...
Abstract We present the photometric analysis of three ultra-short-period total eclipsing binaries in contact configuration, CRTS_J172718.0+431624, OGLE-BLG-ECL-000104, and OGLE-BLG-ECL-000012, mined from massive astronomical surveys. Using available archival light curves (LCs) Vista Variables Vía Láctea (VVV), Optical Gravitational Lensing Experiment (OGLE), Zwicky Transient Facility, Catalina Sky Survey different passbands new multiband observations with 2.3 m Aristarchos telescope at...
A deep Hα image of interlocking filamentary arcs nebulosity has been obtained with a wide-field (≈30° diameter) narrow-band filter camera combined charge-coupled device as detector. The resultant mosaic images, extending to galactic latitude −65°, corrected for field distortions and had coordinates superimposed on it permit accurate correlations the most recent H i (21 cm), X-ray (0.75 keV) FIR (IRAS 100 μm) maps.
Deep optical CCD images of the supernova remnant G 15.1-1.6 were obtained where filamentary and diffuse emission was discovered. The images, taken in lines H], [S ii], [], reveal structures all around remnant. radio at 4850 MHz same area is found to be strongly correlated with brightest filaments. IRAS 60 μm may also but a lesser extent. flux-calibrated suggest that originates from shock-heated gas ([S ii]/Hα > 0.4), while there possible region ~ 0.3) contaminating remnant's east....
We present a detailed investigation of the low-amplitude contact binary HI Dra based on new VRcIc CCD photometric light curves (LCs) combined with published radial velocity (RV) curves. Our completely covered LCs were analyzed using PHOEBE and revealed that is an overcontact low fill-out factor f = 24 ± 4(%) temperature difference between components 330 K. Two spotted models are proposed to explain LC asymmetry, which A subtype W UMa type eclipsing systems, cool spot less massive cooler...
ABSTRACT We present 126 eclipsing binary candidates among 4683 Catalina Sky Surveys (CSS) detached and semi-detached systems (EBs) showing cyclic or quadratic period variations over a 12 yr time span. By using inverse Gaussian profiles of the eclipses coupled with Markov chain Monte Carlo procedure, times minima (ToM) were calculated diagrams eclipse timing (ETVs) constructed. Numerical tests performed, involving synthetic EBs generated by PHOEBE 2.0 engine actual data for well-known from...
Abstract We present an effective strategy for extensive analysis of eclipsing time variations (ETVs) using modern and sophisticated optimization methods that comprise a set tools to investigate period variability mechanisms in binary stars such as the light-time effect, Applegate mechanism, mass transfer. implement these first assuming above can act simultaneously puzzling W UMa–type star TZ Bootis by archival new TESS data spanning 75 yr reexamining up-to-date ETVs. Preliminary revealed...
Abstract We present the physical properties for 2281 northern eclipsing binary (EB) stars with Algol (EA)-type light-curve (LC) morphology, based on data extracted from Catalina Sky Survey (CSS). Our study is analysis of Eclipsing Binary via Artificial Intelligence (EBAI) artificial neural network (ANN) tool. An intensive search optimal ANN topology was performed. In order to feed LCs that are representative CSS observations, two independent methods, template fitting and Two-Gaussian Model,...
During an [O iii] survey of planetary nebulae, we identified a region in Sagittarius containing several candidate supernova remants (SNRs) and obtained deep optical narrow-band images spectra to explore their nature. We the area interest by acquiring observations emission lines Hα + [N ii] , [S . The resulting mosaic covers 1.4° × 1.0°, where both filamentary diffuse was discovered, suggesting that there is more than one SNR area. Deep long-slit were also taken eight different regions. Both...
Spatially resolved profiles of the HeII 6560 A, Halpha and [N II] 6548 & 6584 A nebular emission lines have been obtained in two orthogonal long cuts over Dumbbell planetary nebula. The central emitting volume bright dumbbell structure is shown to be particularly inert with an expansion velocity <= 7 km/s. This enveloped by inner [O III] 5007 shell expanding at 13 km/s, outer 31 km/s which on inside 35 new + continuum-subtracted image 15' diameter halo has also compared recent proper...
We present a multi-band photometric analysis of CRTS J163819.6+03485, the first low mass ratio (LMR) contact binary system with period under (CB) limit. The unprecedented combination and makes this unique for eclipsing (EB) research. Using new observations, we explored parameter space total EB through detailed scan in - inclination plane using PIKAIA genetic algorithm optimizer. best set relative physical parameters corresponding uncertainties was adopted Markov Chain Monte Carlo sampling...
We present the first multicolor CCD photometry for eclipsing binary V380 Cassiopeia (V380 Cas) observed on 34 nights in 2009 and 2010 at University of Patras Observatory. The PHOEBE program based Wilson–Devinney algorithm was used to analyze complete BVRc Ic light curves. It found that Cas misclassified it is a well-detached system consisting two main-sequence stars. A range solutions give satisfactory fits observations also investigated. orbital solution photometric mass ratio q = 1.08...
Abstract Low-mass ratio systems (LMR) are a very interesting class of contact eclipsing binaries challenging the theoretical models stability. These also considered possible progenitors rare low-mass optical transients called red novae. In this study, we present identification 7 new totally LMR from Catalina Sky Surveys (CSS) and 77 candidates All Automated Survey. Using available CSS light curves multiband observations for CSS_J210228.3-031048 CSS_J231513.3+345335 with 2.3 m Aristarchos...
Recent period investigations of the Post-Common Envelop Binary (PCEB) NSVS 14256825 suggested that two circumbinary companions were necessary to explain observed Eclipse Timing Variations (ETVs). Our objective was search for best-fitting curve LTTE terms in ETV diagram, implementing a grid optimization scheme Keplerian (kinematic) and Newtonian (N-body) fits, alongside dynamical stability analysis N-body simulations. We compiled datasets archival photometric data covering different timeline...