M. Andreev
A5030931416- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Planetary Science and Exploration
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Isotope Analysis in Ecology
- Nuclear Physics and Applications
- Solar and Space Plasma Dynamics
- High-pressure geophysics and materials
- Calibration and Measurement Techniques
- SAS software applications and methods
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Geophysics and Gravity Measurements
- Space Exploration and Technology
- Atmospheric Ozone and Climate
- Atomic and Subatomic Physics Research
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Advanced Memory and Neural Computing
Sungkyunkwan University
2022-2024
National Academy of Sciences of Ukraine
2010-2024
Main Astronomical Observatory
2010-2024
International Center for Astronomical, Medical and Ecological Research
2011-2020
Russian Academy of Sciences
2010-2019
Kabardino-Balkarian Scientific Center
2010-2019
Institute of Astronomy
2010-2019
Institute of Applied Astronomy
2010-2018
Seikei University
2014
Lomonosov Moscow State University
2014
We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to September 2009, for total 76 GRBs, and present an additional three pre-Swift not included in earlier sample. Furthermore, we publish 840 new points 42 GRB afterglows, sets 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A 080810. analyzed light curves all derived spectral energy distributions with best quality, allowing us estimate host...
Abstract We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution superhump is found to be composed three distinct stages: an early evolutionary stage with a longer period, middle varying periods, final shorter, stable period. During stage, systems periods less than 0.08 d show positive derivatives. present observational characteristics these stages give greatly improved...
Continuing the project described by Kato et al. (2009, arXiv:0905.1757), we studied 86 SU UMa-type dwarf novae. We confirmed general trends such as relation between period derivatives and orbital periods. There are some systems showing positive despite long observed 2011 outburst of WZ Sge-type nova BW Scl, recorded an O-C diagram similar to those previously known The OT J184228.1+483742 showed unusual pattern double outbursts composed with early superhumps one ordinary superhumps. propose...
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....
Abstract Continuing the project described by Kato et al. (2009, PASJ, 61, S395), we collected times of superhump maxima for 51 SU UMa-type dwarf novae, mainly observed during 2010–2011 season. Although most new data systems with short periods basically confirmed findings (ibid.) and (2010, 62, 1525), long-period system GX Cas showed an exceptionally large positive-period derivative. An analysis public Kepler V344 Lyr V1504 Cyg yielded less-striking stage transitions. In Lyr, there was a...
Continuing the project described by Kato et al. (2009a, arXiv:0905.1757), we collected times of superhump maxima for SU UMa-type dwarf novae mainly observed during 2012-2013 season. We found three objects (V444 Peg, CSS J203937 and MASTER J212624) having strongly positive period derivatives despite long orbital (Porb). By using growing stage (stage A) superhumps, obtained mass ratios six objects. characterized nine new WZ Sge-type novae. made a pilot survey decline rate slowly fading part...
Continuing the project described by Kato et al. (2009, arXiv:0905.1757), we collected times of superhump maxima for 102 SU UMa-type dwarf novae observed mainly during 2014-2015 season and characterized these objects. Our has greatly improved statistics distribution orbital periods, which is a good approximation cataclysmic variables at terminal evolutionary stage, confirmed presence period minimum 0.053 d spike just above this period. The number density monotonically decreased toward longer...
Abstract Continuing the project described by Kato et al. (2009, PASJ, 61, S395), we collected times of superhump maxima for 128 SU UMa-type dwarf novae observed mainly during 2015–2016 season and characterized these objects. The data have improved distribution orbital periods, relation between period variation superhumps, variations rebrightening type in WZ Sge-type Coupled with new measurements mass ratios using growing stages now a clearer statistically greatly evolutionary path near...
We present a comprehensive analysis of bright, long duration (T90 ~ 257 s) GRB 110205A at redshift z= 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the still radiating in gamma-ray band. Nearly 200 s observations were obtained simultaneously from optical, X-ray to gamma-ray, which makes it one exceptional cases study broadband spectral energy distribution across 6 orders magnitude during phase. By fitting time resolved spectra, we clearly...
Context. In a previous paper we reported planetary companion to the young and very active K5Ve star BD+20 1790. We found that this has high level of stellar activity () manifests in plethora phenomena (starspots, prominences, plages, large flares). Based on careful study these features deep discussion analysis effects radial velocity measurements, demonstrated presence planet provided best explanation for variations all peculiarities star. The orbital solution resulted close-in massive with...
Abstract We report on the analysis of 34 years photometric observations pulsating helium atmosphere white dwarf GD358. The complete data set includes archival from 1982 to 2006, and 1195.2 hr new 2007 2016. From this set, we extract 15 frequencies representing g-mode pulsation modes, adding 4 modes 11 known previously. present evidence that these are ℓ = 1 13 which belong a consecutive sequence in radial overtone k . perform detailed asteroseismic using models include parameterized, complex,...
We report on a discovery of "negative" superhumps during the 2011 January superoutburst ER UMa. During which started 16, we detected negative having period 0.062242(9) d, shorter than orbital by 2.2%. No evidence positive was this observation. This finding indicates that disk exhibited retrograde precession superoutburst, contrary to all other known cases superoutbursts. The duration those ordinary superoutbursts and intervals normal outbursts were longer ones. suggest possibility such...
Aims.We report results of a quantitative colorimetric UBVRI analysis two flare events on the red dwarf EV Lac. The photometric data were obtained in September 2004, during multi-site synchronous monitoring from four observatories Ukraine, Russia, Greece, and Bulgaria. These observations confirmed presence small-scale high-frequency oscillations (HFO) initially detected by Rodonó (1974, A&A, 32, 337) recently reconfirmed authors. Here we discuss color characteristics flares HFO.
We report on the analysis of 436.1 hrs nearly continuous high-speed photometry pulsating DB white dwarf GD358 acquired with Whole Earth Telescope (WET) during 2006 international observing run, designated XCOV25. The Fourier transform (FT) light curve contains power between 1000 to 4000 microHz, dominant peak at 1234 microHz. find 27 independent frequencies distributed in 10 modes, as well numerous combination frequencies. Our discussion focuses a new asteroseismological GD358, incorporating...
We present infrared JHK photometry of the cataclysmic variable (CV) SDSS J123813.73 − 033933.0 and analyze it along with optical spectroscopy, demonstrating that binary system is most probably comprised a massive white dwarf Teff = 12000 ± 1000 K brown spectral type L4. The inferred parameters suggest this may have evolved beyond orbital period minimum bounce-back system. stands out among CVs by exhibiting cyclical variability Zharikov et al. called brightenings. These are not related to...
We carried out the photometric observations of SU UMa-type dwarf nova ER UMa during 2011 and 2012, which showed existence persistent negative superhumps even superoutburst. performed two-dimensional period analysis its light curves by using a method called "least absolute shrinkage selection operator" (Lasso) "phase dispersion minimization" (PDM) analysis, we found that systematically changed between superoutburst next The trend change can beinterpreted as reflecting disk radius. This radius...
Abstract Continuing the project undertaken by Kato et al. (2009), we collected times of superhump maxima for 56 SU UMa-type dwarf novae mainly observed during 2013–2014 season and characterized these objects. We detected negative superhumps in VW Hyi indicated that low number normal outbursts some supercycles can be interpreted as a result disk tilt. This finding, combined with Kepler observation V1504 Cyg V344 Lyr, suggests tilt is responsible modulating outburst pattern novae. also studied...
We observed the 2006 superoutburst of SDSS J080434.20+510349.2 during its plateau phase, rebrightening and post-superoutburst final decline. found that this object is a grazing eclipsing system with period 0.0590048(2) d. Well-defined eclipses were only late stage depth decreased subsequent stages. determined superhump to be 0.059539(11) d, giving fractional excess 0.90(2)%. During phases, persisting superhumps periods longer than those phase: 0.059632(6) phase 0.05969(4) d fading. This...
Context. We analyze the results of our comprehensive observations high-perihelion comet C/2014 B1 (Schwartz) with stable disk-shaped coma and jets in order to study its nature. Aims. The main objective is obtain new observational for a unique disk-like perihelion distance 9.56 au. Methods. Quasi-simultaneous long-slit spectra, as well photometric polarimetric images g-sdss r-sdss filters, were acquired 6 m telescope Special Astrophysical Observatory on 2017 January 23. BVR-band photometry...
PG 1351+489 is one of the 20 DBVs – pulsating helium-atmosphere white dwarf stars known and has simplest power spectrum for this class star, making it a good candidate to study cooling rates. We report accurate period determinations main peak at 489.334 48 s two other normal modes using data from Whole Earth Telescope (WET) observations 1995 2009. In 2009, we detected new pulsation mode exhibited substantial change in its amplitude compared all previous observations. were able estimate...
Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected ESA's mission remain recoverable after their discovery. An observation campaign on potentially hazardous asteroid (99 942) Apophis was conducted during asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, test coordination and evaluate overall performance Gaia-FUN-SSO . The 2732 high quality astrometric...