Georgios Filippos Paraschos
A5069773046- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Neutrino Physics Research
- Particle Accelerators and Free-Electron Lasers
- Galaxies: Formation, Evolution, Phenomena
- Dark Matter and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Laser-Plasma Interactions and Diagnostics
- Gyrotron and Vacuum Electronics Research
- GNSS positioning and interference
- Particle Dynamics in Fluid Flows
- Mechanics and Biomechanics Studies
- Heat Transfer Mechanisms
- Solar and Space Plasma Dynamics
- Precipitation Measurement and Analysis
- Cyclone Separators and Fluid Dynamics
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Experimental and Theoretical Physics Studies
- Nuclear reactor physics and engineering
Max Planck Institute for Radio Astronomy
2020-2025
Center for Astrophysics Harvard & Smithsonian
2022-2023
Sejong University
2022-2023
Korea Astronomy and Space Science Institute
2022-2023
University of Würzburg
2023
University College Cork
2023
University of Bologna
2023
Kyungpook National University
2023
Joint Institute for VLBI ERIC
2023
National Observatory of Athens
2022
3C84 is a nearby radio source with complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates use VLBI above hitherto available maximum frequency 86GHz. Using ultrahigh resolution observations at highest 228GHz, we aim to directly detect compact structures understand physical conditions in 3C84. We used EHT 228GHz and, given limited (u,v)-coverage, applied geometric model fitting data. also employed...
The 2017 observing campaign of the Event Horizon Telescope (EHT) delivered first very long baseline interferometry (VLBI) images at frequency 230 GHz, leading to a number unique studies on black holes and relativistic jets from active galactic nuclei (AGN). In total, eighteen sources were observed: main science targets, Sgr A* M87 along with various calibrators. We investigated morphology sixteen AGN in EHT data set, focusing properties VLBI cores: size, flux density, brightness temperature....
The 2017 observing campaign of the Event Horizon Telescope (EHT) delivered first very long baseline interferometry (VLBI) images at frequency 230,GHz, leading to a number unique studies on black holes and relativistic jets from active galactic nuclei (AGN). In total, eighteen sources were observed, including main science targets, Sgr,A* M,87, various calibrators. Sixteen AGN. We investigated morphology sixteen AGN in EHT data set, focusing properties VLBI cores: size, flux density,...
AGN-launched jets are a crucial element in the study of supermassive black holes (SMBH) and their closest surroundings. The formation such jets, whether they launched by magnetic field lines anchored to accretion disc or directly connected hole's (BH) ergosphere, is subject ongoing, extensive research. 3C84, compact radio source central galaxy NGC1275 Perseus super-cluster, prime laboratory for testing jet launching scenarios, as well studying innermost, sub-parsec AGN structure origin. Very...
The X-ray polarization observations, made possible with the Imaging Polarimetry Explorer (IXPE), offer new ways of probing high-energy emission processes in astrophysical jets from blazars. Here, we report first observation blazar S4 0954+65 a high optical and state. During our multi-wavelength (MWL) campaign source, detected an flare whose peak coincided flare. This optical-X-ray most likely took place feature moving along parsec-scale jet, imaged at 43 GHz by Very Long Baseline Array...
The connection between γ-ray flares and blazars is a topic of active research. Few sources exhibit outbursts distinct enough to be conclusively connected with features in their jet morphology. Here we present an investigation the sole flare blazar date how it associated its structure, as revealed by very long baseline interferometry (VLBI). We find that throughout course flare, fractional linear polarisation increases VLBI electric vector position angles (EVPAs) rotate become perpendicular...
The connection between $\gamma$-ray flares and blazars is a topic of active research, with few sources exhibiting distinct enough such outbursts to be able conclusively connect them features in their jet morphology. Here we present an investigation the sole flare blazar OJ 248 thus far, association its structure, as revealed by very long baseline interferometry (VLBI). We find that throughout course flare, fractional linear polarisation increases 248, VLBI electric vector position angles...
Active galactic nuclei (AGN) are some of the most luminous and extreme environments in Universe. The central engines AGN believed to be super-massive black-holes (SMBHs) fed by accretion discs threaded magnetic fields within a dense magneto-ionic medium. We report our findings from polarimetric very-long-baseline interferometry (VLBI) observations quasar NRAO,150 taken October 2022 using combined network Very Long Baseline Array (VLBA) Effelsberg 100-m Radio Telescope. These comprise first...
Understanding the creation of relativistic jets originating from active galactic nuclei (AGNs) requires a thorough understanding accompanying plasma instabilities. Our high-sensitivity, high-resolution, global, very-long-baseline-interferometry observations jet in radio galaxy have enabled us to study its inner morphology. We find that thread-like pattern can be described by Kelvin-Helmholtz instability, consisting four instability modes. model favours Mach number M_ j and sound speed α_ On...
Aims. We introduce the TELAMON program which is using Effelsberg 100-m telescope to monitor radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, specifically TeV blazars and candidate neutrino-associated AGN. Here, we present characterize our main sample TeV-detected blazars. Methods. analyzed data from first ∼2.5 yr observations between August 2020 February 2023 range 14 GHz 45 GHz. During this pilot phase, observed all 59 Northern Hemisphere (i.e., Dec...
The spatial scales of relativistic radio jets, probed by magneto-hydrodynamic (RMHD) jet launching simulations and most very long baseline interferometry (VLBI) observations differ an order magnitude. Bridging the gap between these RMHD VLBI requires selecting nearby active galactic nuclei (AGN), parsec-scale region which can be resolved. source 3C 84 is a bright AGN fulfilling necessary requirements: it powerful, powered central supermassive black hole, while also being bright. Using 22 GHz...
Nearby radio galaxies that contain jets are extensively studied with VLBI, addressing jet launching and the physical mechanisms at play around massive black holes. 3C 84 is unique in this regard, because combination of its proximity large SMBH mass provides a high spatial resolution to resolve complex structure base. For an angular scale 50 ${\mu}$as corresponds 200 - 250 Schwarzschild radii ($R_s$). Recent RadioAstron VLBI imaging 22 GHz revealed east-west elongated feature northern end...
3C84 (NGC1275) is one of the brightest radio sources in mm radio-bands, which led to a plethora VLBI observations at numerous frequencies over years. They reveal two-sided jet structure, with an expanding but not well-collimated parsec-scale jet, pointing southward. High resolution mm-VLBI allow study and imaging base on sub-parsec scale. This could facilitate investigation nature origin, also view previously detected two-railed structure east-west oriented core region seen RadioAstron 22...
Total intensity variability light curves offer a unique insight into the ongoing debate about launching mechanism of jets. For this work, we utilise availability radio and $\gamma$-ray over few decades source 3C 84 (NGC 1275). We calculate multiband time lags between flares identified in via discrete cross-correlation Gaussian process regression. find that jet particle magnetic field energy densities are equipartition ($k_\textrm{r} = 1.08\pm0.18$). The apex is located $z_\textrm{91.5 GHz}=...
We present James Webb Space Telescope MIRI data of the inner ~3x2 kpc^2 galaxy IC5063, in which jets a supermassive black hole interact with gaseous disk they are crossing. Jet-driven outflows were known to be initiated along or near jet path, and stability conditions clouds vary because these outflows. The data, unprecedented resolution sensitivity infrared, now reveal that there more than ten discrete regions outflows, nearly doubling number such regions. Outflows exist radio lobes, at...
Abstract We present James Webb Space Telescope MIRI data of the inner ∼3 × 2 kpc galaxy IC 5063, in which jets a supermassive black hole interact with gaseous disk they are crossing. Jet-driven outflows were known to be initiated along or near jet path and modify stability molecular clouds, possibly altering their star formation properties. The data, unprecedented resolution sensitivity infrared, now reveal that there more than 10 discrete regions outflows, nearly doubling number such...
ABSTRACT 3C 84 (NGC 1275) is the radio source at centre of Perseus cluster and exhibits a bright jet. We observed with Global Millimeter VLBI Array (GMVA) between 2008 2015, typical angular resolution ∼50 $\mu$as. The observations revealed consistent double nuclear structure separated by ∼770 gravitational radii assuming black hole mass 3.2 × 108 M⊙. region likely too broad to be true jet base anchored in accretion disc or ergosphere. A cone parabola were fit stacked (time averaged) image...
In the past years, evidence has started piling up that some high-energy cosmic neutrinos can be associated with blazars in flaring states. On February 26, 2022, a new blazar-neutrino coincidence been reported: track-like neutrino event IC220225A detected by IceCube is spatially coincident flat-spectrum radio quasar PKS 0215+015. Like previous associations, this source was found to high optical and ${\gamma}$-ray state. Moreover, showed bright outburst, which substantially increases...
One of the most well-known extragalactic sources in sky, quasar 3C 454.3 , shows a curved parsec-scale jet that has been exhaustively monitored with very-long-baseline interferometry (VLBI) over recent years. In this work, we present comprehensive analysis four years high-frequency VLBI observations at 43 GHz and 86 GHz, between 2013–2017, total intensity linear polarization. The images obtained from these enabled us to study structure magnetic field topology source on spatial scales down...
The detection of cosmic neutrinos has raised many new questions in astroparticle physics, among the most compelling which is identification neutrino emitters. After more than a decade IceCube operations, promising astrophysical association remains very-high-energy (VHE, $>100$ GeV) blazar TXS 0506+056. Recently, on November 14, 2020 observatory reported well-reconstructed high-energy event, IceCube-201114A, with high probability being astrophysical. Within 90% IceCube-201114A localization...
Aims. We introduce the TELAMON program which is using Effelsberg 100-m telescope to monitor radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, specifically TeV blazars and candidate neutrino-associated AGN. Here, we present characterize our main sample TeV-detected blazars. Methods. analyze data from first ~2.5 years observations between August 2020 February 2023 range 14 GHz 45 GHz. During this pilot phase, have observed all 59 Northern Hemisphere (i.e.,...
The spatial scales of relativistic radio jets, probed by magneto-hydrodynamic jet launching simulations (RMHDs) and most very-long-baseline interferometry (VLBI) observations differ an order magnitude. Bridging the gap between these RMHD VLBI requires selecting nearby active galactic nuclei (AGN), parsec-scale region which can be resolved. 3C 84 is a bright AGN fulfilling necessary requirements: it powerful, powered central supermassive black hole, while also being very bright. Using 22 GHz...
Radio galaxies harbouring jetted active galactic nuclei are a frequent target of very-long-baseline interferometry (VLBI) because they play an essential role in exploring how jets form and propagate. Hence, only few have not been detected with VLBI yet; Fornax A is one the most famous examples. Here we present first detection compact core region VLBI. At 8.4 GHz faint consistent unresolved point source. We constrained its flux density to be $S_0 = 47.5-62.3\,\textrm{mJy}$ diameter...
Radio galaxies harbouring jetted active galactic nuclei are a frequent target of very long baseline interferometry (VLBI) because they play an essential role in our exploration how jets form and propagate. Hence, only few have not yet been detected with VLBI; Fornax A was one the most famous examples. Here we present first detection compact core region VLBI. At 8.4 GHz faint is consistent unresolved point source. We constrained its flux density to be S 0 = 47.5 − 62.3 mJy diameter D min ≤ 70...