A5008057645- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Industrial Engineering and Technologies
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Atomic and Subatomic Physics Research
- Engineering Diagnostics and Reliability
- Elevator Systems and Control
- X-ray Spectroscopy and Fluorescence Analysis
- Atmospheric Ozone and Climate
- Radiation Detection and Scintillator Technologies
- Solid-state spectroscopy and crystallography
- Satellite Image Processing and Photogrammetry
- Gamma-ray bursts and supernovae
- Gyrotron and Vacuum Electronics Research
- Construction Management and Sustainability
- Astrophysics and Cosmic Phenomena
- Advanced X-ray Imaging Techniques
Shumen University
2016-2024
Institute of Astronomy and National Astronomical Observatory
2012-2020
American Association of Variable Star Observers
2020
Siberian State Automobile and Highway University
2017
The transiting planet WASP-12 b was identified as a potential target for transit timing studies because departure from linear ephemeris reported in the literature. Such deviations could be caused by an additional system. We attempt to confirm existence of claimed variations and interpret its origin. organised multi-site campaign observe transits three observing seasons, using 0.5-2.6-metre telescopes. obtained 61 light curves, many them with sub-millimagnitude precision. simultaneous...
There have been previous hints that the transiting planet WASP-3 b is accompanied by a second in nearby orbit, based on small deviations from strict periodicity of observed transits. Here we present 17 precise radial velocity measurements and 32 transit light curves were acquired between 2009 2011. These data used to refine parameters host star planet. This has resulted reduced uncertainties for radii masses The radial-velocity times show no evidence an additional system. Therefore,...
Abstract Photometric observations of 12 totally eclipsing W UMa binaries (NSVS 3325547, V646 Lac, V1320 Cas, V539 Dra, V816 Cep, NSVS 9045055, V1115 V902 V596 Peg, 1768818, V619 and 3198272) are presented. We found that the longer (in phase units) flat eclipses are, smaller mass ratios (or reciprocal values) are. The five targets turned out close to lower-mass ratio limit. periods Cas Lac increase, while Peg decreases. Masses, radii, luminosities target components were calculated by...
We present photometric observations in Sloan filters g', i' of the eclipsing W UMa stars USNO-A2.0 1350-17365531, V471 Cas, V479 Lac and V560 Lac. The sinusoidal-like O-C diagram Cas shows presence third body with mass 0.12 Msun (red dwarf) at distance 897 Rsun. reveals period decreasing. results light curve solutions are: (i) targets are overcontact binaries small fill-out factors; (ii) Their components F-K stars, comparable size, whose temperature differences below 80 K; (iii) All undergo...
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...
In 2016 May, the intermediate polar FO~Aqr was detected in a low state for first time its observational history. We report time-resolved photometry of system during initial recovery from this faint state. Our data, which includes high-speed with cadences just 2 sec, shows existence very strong periodicities at 22.5 min and 11.26 min, equivalent to spin-orbit beat frequency twice value, respectively. A pulse spin is also present but much lower amplitude than normally observed bright By...
Photometric observations of the W UMa binaries USNO-B1.0 1452–0049820 and ASAS J102556+2049.3 are presented. The results from light curve solutions as follows: (i) component temperatures T1 = 6400 K T2 6300 for 6000 5930 J102556+2049; (ii) photometric mass ratios well determined because targets undergo total eclipses; (iii) both close to lower mass-ratio limit (0.111 0.131 correspondingly); (iv) fillout factors two unexpectedly small (0.045 0.243, respectively) their ratios. global...
Photometric observations in Sloan g' and i' bands of four W UMa stars, NSVS 2244206, 908513, CSS J004004.7+385531, VSX J062624.4+570907, are presented. The light curve solutions reveal that all targets have overcontact configurations with fillout factor within 0.15-0.26. Their components G-K spectral type almost thermal contacts. They relatively close also size luminosity: the radius rations r_2/r_1 0.75-0.90; luminosity ratios l_2/l_1 0.53-0.63. results solution J004007.7+385531 imply weak...
PDS 110 is a young disk-hosting star in the Orion OB1A association. Two dimming events of similar depth and duration were seen 2008 (WASP) 2011 (KELT), consistent with an object closed periodic orbit. In this paper we present data from ground-based observing campaign designed to measure both photometrically spectroscopically during time predicted eclipse September 2017. Despite high-quality photometry, did not occur, although coherent structure suggesting variable amounts stellar flux or...
The paper presents light curve solutions of our observations four new ultrashort-period eclipsing binaries with MS components. Two them have periods almost at the upper limit (0.22 days) binaries, while around 0.18 days CSS J171508.5+350658 and J214633.8+120016 are amongst shortest known orbital periods. J171410.0+ 445850, J224326.0+154532 over contact fill out factors 0.25 is a semidetached system. two targets consist M dwarfs.
We report optical charge‐coupled device (CCD) photometry of the recently identified symbiotic star EF Aquilae (EF Aql). Our observations in Johnson V and B bands clearly show presence stochastic light variations with an amplitude about 0.2 mag on a time scale minutes. The point toward white dwarf (WD) as hot component system. It is 11th object among more than 200 stars known detected flickering. Estimates mass accretion rate onto WD loss wind Mira secondary lead to conclusion that less 1%...
Photometric observations of the W UMa binary NSVS 2569022 are presented. The light curve solution reveals that both components F spectral type (temperatures T1 = T2 6100 K). undergoes a total eclipse subtype and mass ratio is well-determined. Its extremely small value only 0.077 implies target will probably experience instability possible merger. This ranks in sixth place among binaries with smallest ratio. Based on an empirical relation "period – mass" for low mass-ratio binaries, we...
Photometric and spectral observations of the W UMa binaries NSVS 4161544 1SWASP J034501.24+493659.9 with periods around 8 hr are presented. The simultaneous light-curve radial-velocity-curve solutions revealed that two targets have over-contact configurations, their components undergo partial eclipses. derived parameters are: mass ratio q = 3.377, orbital inclination i 65.00, temperatures T1 6016 K T2 5726 K, masses M1 0.43 M2 1.47 radii R1 0.74 R2 1.28 luminosities L1 0.64 L2 1.51 . 2.378,...
Abstract The intermediate polar FO Aquarii (FO Aqr) experienced its first reported low-accretion states in 2016, 2017, and 2018, and, using newly available photographic plates, we identify prediscovery low 1965, 1966, 1974. primary focus of our analysis, however, is an extensive set time-series photometry obtained between 2002 with particularly intensive coverage the 2016–2018 states. After computing updated spin ephemeris for white dwarf (WD), show that period began to increase 2014 after...
Photometric and spectral observations of the W UMa binaries NSVS 254037 V505 Lac with periods around 8 hr are presented. The simultaneous light curve radial velocity solutions revealed that their components G type. two targets undergo partial eclipses. They both have overcontact configurations subtype fill‐out factor f ∼ 0.1. derived parameters are: mass ratio q = 2.42; orbital inclination i 67.1°; temperatures T 1 5800 K 2 5585 K; masses M 0.47 ⊙ 1.15 ; radii R 0.72 1.07 luminosities L 0.53...
Photometric observations in Sloan g' and i' bands of W UMa binaries NSVS 4340949, T-Dra0–00959, GSC 03950–00707, 4665041, 4803568, MM Peg, Com 4751449 are presented. The light curve solutions revealed that the components each target G K spectral types. sample have middle-contact configurations whose fillout factors within range 0.2–0.4. only exception is which deeper contact (fillout factor 0.55). It precisely obeys relation between mass ratio for deep, low overcontact binaries. One eclipses...