M. G. Nikolashvili
A5032352530- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Astrophysics and Star Formation Studies
- Computational Physics and Python Applications
- Calibration and Measurement Techniques
- Particle accelerators and beam dynamics
- Particle physics theoretical and experimental studies
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- Particle Detector Development and Performance
- Superconducting Materials and Applications
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
Heidelberg University
2020-2024
Abastumani Astrophysical Observatory
2015-2024
Southampton City Council
2015
Institute of Applied Astronomy
2010-2011
Georgian National Academy of Sciences
2008
Astronomical Observatory
1998
We present results from monitoring the multi-waveband flux, linear polarization, and parsec-scale structure of quasar PKS 1510-089, concentrating on eight major gamma-ray flares that occurred during interval 2009.0-2009.5. The peaks were essentially simultaneous with maxima at optical wavelengths, although flux ratio two wavebands varied by an order magnitude. polarization vector rotated 720 degrees a 5-day period encompassing six these flares. This culminated in very bright, roughly 1 day,...
Following the detection of strong TeV γ-ray flares from BL Lac object 1ES 1959+650 with Whipple 10 m Cerenkov telescope on 2002 May 16 and 17, we performed intensive target opportunity radio, optical, X-ray, observations 18 to August 14. Observations X-ray Rossi X-Ray Timing Explorer HEGRA telescopes revealed several flares, enabling us sensitively test X-ray-γ-ray flux correlation properties. Although fluxes seemed be correlated in general, found an "orphan" flare that was not accompanied...
Eight optical and four radio observatories have been intensively monitoring the BL Lac object 0716+714 in last years: 4854 data points collected UBVRI bands since 1994, while light curves extend back to 1978. Many of these are presented here for first time. The long-term trend shown by seems vary with a characteristic time scale about 3.3 years, longer period 5.5-6 years characterize variations. In general, colour indices only weakly correlated brightness. flux behaviour at different...
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during first two years Fermi Gamma-ray Space Telescope mission. While investigating previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that emission appears delayed with respect to gamma-ray about 10 days. X-ray reveal pair `isolated' flares separated ~90 days, only weak counterparts. The spectral structure measured...
We analyze the multifrequency behavior of quasar 3C 454.3 during three prominent \gamma-ray outbursts: 2009 Autumn, 2010 Spring, and Autumn. The data reveal a repeating pattern, including triple flare structure, in properties each outburst, which implies similar mechanism(s) location for all events. multi-frequency indicates that lower frequency events are co-spatial with outbursts, although emission varies on shortest timescales. determine variability from UV to IR wavelengths an outburst...
We present the results of extensive multi-waveband monitoring blazar 3C~279 between 1996 and 2007 at X-ray energies (2-10 keV), optical R band, 14.5 GHz, as well imaging with Very Long Baseline Array (VLBA) 43 GHz. In all bands power spectral density corresponds to "red noise" that can be fit by a single law over sampled time scales. Variations in flux three wavebands are significantly correlated. The delay high low frequency changes substantially on scales years. A major multi-frequency...
We present observations of a major outburst at centimeter, millimeter, optical, X-ray, and γ-ray wavelengths the BL Lacertae object AO 0235+164. analyze timing multi-waveband variations in flux linear polarization, as well changes Very Long Baseline Array images λ = 7 mm with ∼0.15 milliarcsec resolution. The association events different wavebands is confirmed high statistical significance by probability arguments Monte Carlo simulations. A series sharp peaks optical pronounced maximum...
Since the launch of Fermi satellite, BL Lacertae has been moderately active at gamma-rays and optical frequencies until May 2011, when source started a series strong flares. The exceptional sampling achieved by GLAST-AGILE Support Program (GASP) Whole Earth Blazar Telescope (WEBT) in collaboration with Steward Observatory allows us to perform detailed comparison daily gamma-ray observations Fermi. Discrete correlation analysis between emission reveals time lag 0 +- 1 d, which suggests...
The BL Lacertae object AO 0235+16 is well known for its extreme optical and radio variability. New data have been collected in the last four years by a wide international collaboration, which confirm intense activity of this source: on long term, overall variations R band up to factor 18 fluxes were detected, while short-term variability few hours one day was observed band. also include results Whole Earth Blazar Telescope (WEBT) first-light campaign organized November 1997, involving dozen...
We present UBVRI light curves of BL Lacertae from May 2000 to January 2001, obtained by 24 telescopes in 11 countries. More than 15000 observations were performed that period, which was the extension Whole Earth Blazar Telescope (WEBT) campaign originally planned for July-August 2000. Rapid flux oscillations are all time, involving variations up a few tenths mag on hour time scales, and witnessing an intense intraday activity this source. Colour indexes have been derived coupling highest...
Of the blazars detected by EGRET in GeV γ-rays, 3C 279 is not only best observed but also one of monitored at lower frequencies. We have assembled 11 spectra, from GHz radio through time intervals observations. Although some data appeared previous publications, most are new, including taken during high states early 1999 and 2000. All spectra show substantial γ-ray contribution to total luminosity object; a state, dominates over that all other frequencies factor more than 10. There no clear...
The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. maximum brightness detected was R = 12.0, which represents the most luminous state thus far observed (M_B ~ -31.4). In order to follow emission behaviour of source detail, a large multiwavelength campaign organized by Whole Earth Blazar Telescope (WEBT). Continuous optical, near-IR monitoring performed several bands. ToO pointings Chandra INTEGRAL satellites provided...
BL Lacertae has been the target of four observing campaigns by Whole Earth Blazar Telescope (WEBT) collaboration. In this paper we present $UBVRI$ light curves obtained WEBT from 1994 to 2002, including last, extended Lac 2001 campaign. A total about 7500 optical observations performed 31 telescopes Japan Mexico have collected, be added $\sim 15600$ Campaign 2000. All these data allow one follow source emission behaviour with unprecedented detail. The analysis colour indices reveals that...
Aims. Since the CGRO operation in 1991–2000, one of primary unresolved questions about blazar γ-ray emission has been its possible correlation with low-energy (in particular optical) emission. To help answer this problem, Whole Earth Blazar Telescope (WEBT) consortium organized GLAST-AGILE Support Program (GASP) to provide optical-to-radio monitoring data be compared detections by AGILE and GLAST satellites. This new WEBT project started early September 2007, just before a strong detection...
Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during last four years it exhibited more than one γ-ray flare per year, becoming most active in sky. We present for first time multi-wavelength AGILE, Swift, INTEGRAL, GASP-WEBT data collected order to explain extraordinary of which occurred 2010 November. On November 20 (MJD 55520), reached a peak flux (E >100 MeV) Fpγ = (6.8 ± 1.0) × 10−5 photons cm−2 s−1 on timescale about 12 hr, factor six...
Context. Over the past few years, on several occasions, large, continuous rotations of electric vector position angle (EVPA) linearly polarized optical emission from blazars have been reported. These events are often coincident with high energy γ-ray flares and they attracted considerable attention, since could allow us to probe magnetic field structure in emitting region jet. The flat-spectrum radio quasar 3C 279 is one most prominent examples showing this behaviour.
Abstract In an effort to locate the sites of emission at different frequencies and physical processes causing variability in blazar jets, we have obtained high time-resolution observations BL Lacertae over a wide wavelength range: with Transiting Exoplanet Survey Satellite (TESS) 6000–10000 Å 2 minute cadence; Neil Gehrels Swift satellite optical, UV, X-ray bands; Nuclear Spectroscopic Telescope Array hard Fermi Large Area γ -ray energies; Whole Earth Blazar for measurement optical flux...
Abstract In this work, we present 8523 pairs of R -band optical photometry observations for the quasar 3C 454.3 made during period 2006 October–2018 February on 70 cm meniscus telescope at Abastumani Observatory, Georgia, to study its intraday variabilities (IDVs) and long-term variations, have come following results. (1) We detected 10 outbursts, a Δ = 3.825 mag variation, some IDVs. The IDV timescales are from 4.1 285 minutes, with corresponding variability amplitude being A 2.9%–43.67%....
Aims. The Whole Earth Blazar Telescope (WEBT) consortium has been monitoring the blazar 3C 454.3 from radio to optical bands since 2004 study its emission variability properties.
The blazar 3C 454.3 underwent an unprecedented optical outburst in spring 2005. This was first followed by a mm and then cm radio outburst, which peaked February 2006. We report on follow-up observations the WEBT to study multiwavelength emission post-outburst phase. XMM-Newton July December 2006 added information X-ray UV fluxes. source faint state. flux at higher frequencies showed fast decreasing trend, represents tail of big outburst. It quiescent state, common all frequencies. In...