Vladimir Kouprianov
A5065037262- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Planetary Science and Exploration
- History and Developments in Astronomy
- Astrophysics and Star Formation Studies
- Medical Imaging Techniques and Applications
- Radio Astronomy Observations and Technology
- Space Satellite Systems and Control
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Particle Accelerators and Free-Electron Lasers
- Neutrino Physics Research
- Galaxies: Formation, Evolution, Phenomena
- SAS software applications and methods
- Atomic and Subatomic Physics Research
- Quantum chaos and dynamical systems
- High-pressure geophysics and materials
- Gyrotron and Vacuum Electronics Research
- CCD and CMOS Imaging Sensors
University of North Carolina at Chapel Hill
2017-2025
Pulkovo Observatory
2011-2023
Adıyaman University
2023
Taras Shevchenko National University of Kyiv
2023
Osaka Kyoiku University
2023
University of Delaware
2023
Appalachian State University
2023
Russian Academy of Sciences
2004-2010
Thammasat University
2001
During the second observing run of Laser Interferometer gravitational- wave Observatory (LIGO) and Virgo Interferometer, a gravitational-wave signal consistent with binary neutron star coalescence was detected on 2017 August 17th (GW170817), quickly followed by coincident short gamma-ray burst trigger Fermi satellite. The Distance Less Than 40 (DLT40) Mpc supernova search performed pointed follow-up observations sample galaxies regularly monitored survey which fell within combined LIGO+Virgo...
Abstract We present the optical spectroscopic evolution of SN 2023ixf seen in subnight cadence spectra from 1.18 to 15 days after explosion. identify high-ionization emission features, signatures interaction with material surrounding progenitor star, that fade over first 7 days, rapid between observed within same night. compare lines and their relative strength those other supernovae early interaction, finding a close match 2020pni 2017ahn spectrum 2014G at later epochs. To physically...
Abstract We present the densely sampled early light curve of Type II supernova (SN) 2023ixf, first observed within hours explosion in nearby Pinwheel Galaxy (Messier 101; 6.7 Mpc). Comparing these data to recently updated models shock-cooling emission, we find that progenitor likely had a radius 410 ± 10 R ⊙ . Our estimate is model dependent but consistent with red supergiant. These provide good fit starting about 1 day after explosion, despite fact classification spectrum shows signatures...
Abstract Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission gravitational waves (GWs). We show that observations associated binary black hole (BBH) central engine blazar OJ 287 demand inclusion radiation reaction effects beyond quadrupolar order. It turns out even certain hereditary contributions to GW required predict impact flare timings 287. develop an approach incorporates this effect into BBH...
We report on the masses ($M_\mathrm{WD}$), effective temperatures ($T_\mathrm{eff}$) and secular mean accretion rates ($\langle \dot{M} \rangle$) of 43 cataclysmic variable (CV) white dwarfs, 42 which were obtained from combined analysis their $\mathit{Hubble~Space~Telescope}$ ultraviolet data with parallaxes provided by Early Third Data Release $\mathit{Gaia}$ space mission, one dwarf gravitational redshift. Our results double number CV dwarfs an accurate mass measurement, bringing total...
Abstract We perform a comprehensive search for optical precursor emission at the position of SN 2023ixf using data from DLT40, ZTF, and ATLAS surveys. By comparing current set with outburst hydrodynamical model light curves, we find that probability significant within 5 yr explosion is low, circumstellar material (CSM) ejected during any possible likely smaller than ∼0.015 M ⊙ . to toy models, that, if there was outburst, duration must have been shorter ∼100 days typical brightness r ≃ −9...
Abstract We report the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in blazar OJ 287. In binary black hole model, it is associated with an impact secondary accretion disk primary. Our multifrequency observing campaign was set up to search for such signature based prediction made 8 yr earlier. The first I -band results have already been reported by Kishore et al. (2024). Here we combine these data our monitoring R -band. There big change – spectral index 1.0 ± 0.1...
Abstract We present our analysis of the Type II supernova DLT16am (SN 2016ija). The object was discovered during ongoing <?CDATA $D\lt 40\,\mathrm{Mpc}$?> (DLT40) one-day cadence search at $r\sim 20.1\,\mathrm{mag}$?> in “edge-on” nearby ( $D=20.0\pm 4.0\,\mathrm{Mpc}$?> ) galaxy NGC 1532. subsequent prompt and high-cadenced spectroscopic photometric follow-up revealed a highly extinguished transient, with $E(B-V)=1.95\pm 0.15\,\mathrm{mag}$?> , consistent standard extinction law R V = 3.1...
We present high-cadence, comprehensive data on the nearby ($D\simeq33\,\rm{Mpc}$) Type II SN 2017ahn, discovered within $\sim$1 day of explosion, from very early phases after explosion to nebular phase. The observables 2017ahn show a significant evolution over $\simeq470\,\rm{d}$ our follow-up campaign, first showing prominent, narrow Balmer lines and other high-ionization features purely in emission (i.e. flash spectroscopy features), which progressively fade lead spectroscopic similar that...
We present high-cadence optical and ultraviolet light curves of the normal Type Ia supernova (SN) 2021aefx, which shows an early bump during first two days observation. This may be a signature interaction between exploding white dwarf nondegenerate binary companion, or it intrinsic to explosion mechanism. In case former, short duration implies relatively compact main-sequence companion star, although this conclusion is viewing-angle dependent. Our best-fit companion-shocking...
We present high-cadence optical, ultraviolet (UV), and near-infrared data of the nearby ($D\approx23$ Mpc) Type II supernova (SN) 2021yja. Many SNe show signs interaction with circumstellar material (CSM) during first few days after explosion, implying that their red supergiant (RSG) progenitors experience episodic or eruptive mass loss. However, because it is difficult to discover early, diversity CSM configurations in RSGs has not been fully mapped. SN 2021yja, detected within...
Abstract We present photometric and spectroscopic data of SN 2018lab, a low-luminosity Type IIP supernova (LLSN) with V -band peak luminosity −15.1 ± 0.1 mag. 2018lab was discovered by the Distance Less Than 40 Mpc (DLT40) survey only 0.73 days post-explosion, as determined observations from Transiting Exoplanet Survey Satellite (TESS). TESS yield densely sampled, fast-rising, early-time light curve likely powered ejecta–circumstellar medium (CSM) interaction. The blueshifted, broadened...
SN~2018aoz is a Type Ia SN with $B$-band plateau and excess emission in the infant-phase light curves $\lesssim$ 1 day after first light, evidencing an over-density of surface iron-peak elements as shown our previous study. Here, we advance constraints on nature origin based its evolution until nebular phase. Near-peak spectroscopic features show intermediate between two subtypes normal Ia: Core-Normal Broad-Line. The could have contributions from radioactive decay well ejecta interaction...
The bright blazar OJ~287 routinely parades high brightness bremsstrahlung flares, which are explained as being a result of secondary supermassive black hole (SMBH) impacting the accretion disc more massive primary SMBH in binary system. is not rigid but rather bends calculable way due to tidal influence secondary. Below we refer this phenomenon variable level. We begin by showing that these flares occur at times predicted simple analytical formula, based on general relativity inspired...
We conducted a search for luminous outbursts prior to the explosion of Type IIn supernovae (SNe IIn). built sample 27 objects spectroscopically classified as SNe and all located at z < 0.015. Using deep archival SN fields images – taken up nearly 20 yr explosions themselves from transient surveys (PTF, ZTF, DES CHASE) major astronomical observatories (European Southern Observatory, ESO National Optical Astronomy NOAO), we found least one outburst years months before seven IIn, with...
Abstract We present very early photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2023bee, starting about 8 hr after explosion, which reveal a strong excess in optical nearest UV ( U UVW1 ) bands during first several days explosion. This data set allows us to probe nature binary companion exploding white dwarf conditions leading its ignition. find good match Kasen model main-sequence star stings ejecta with shock as they buzz past. Models double detonations, shells...
Abstract We present five far- and near-ultraviolet spectra of the Type II plateau supernova, SN 2022acko, obtained 5, 6, 7, 19, 21 days after explosion, all observed with Hubble Space Telescope/Space Telescope Imaging Spectrograph. The first three epochs are earlier than any supernova has been in far-ultraviolet revealing unprecedented characteristics. These dominated by strong lines, primarily from metals, which contrasts featureless early optical spectra. flux decreases over initial time...
Abstract In this work, we present the results of recent quasi-simultaneous multi-band optical observations (in BVRI) blazar BL Lacertae over diverse timescales. For study, source was observed from September 2020 to October using six different telescopes around world, collecting ∼5800 photometric image frames in BVRI. The displays many episodes significant intraday variability, and amplitude increases with brightness target. Moreover, object also showed variability on a short-term basis, flux...
We present the discovery and high-cadence follow-up observations of SN 2018ivc, an unusual Type II supernova that exploded in NGC 1068 (D=10.1 Mpc). The light curve 2018ivc declines piecewise-linearly, changing slope frequently, with four clear changes first 30 days evolution. This rapidly indicates interaction between circumstellar material ejecta plays a significant role Circumstellar is further supported by strong X-ray detection. spectra are evolving dominated hydrogen, helium, calcium...
Flaring episodes in blazars represent one of the most violent processes observed extra-galactic objects. Studies such events shed light on energetics physical occurring innermost regions blazars, which cannot otherwise be resolved by any current instruments. In this work, we present some largest and rapid flares captured optical band 3C 279, OJ 49, S4 0954+658, TXS 1156+295 PG 1553+113. The source flux was to increase nearly ten times within a timescale few weeks. We applied several methods...