E. Angelakis
A5025945790- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Particle Accelerators and Free-Electron Lasers
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Gyrotron and Vacuum Electronics Research
- Astronomy and Astrophysical Research
- Particle Detector Development and Performance
- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Particle physics theoretical and experimental studies
- Computational Physics and Python Applications
- Gut microbiota and health
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Calibration and Measurement Techniques
- Nuclear Physics and Applications
- GNSS positioning and interference
- Pulsars and Gravitational Waves Research
- Astro and Planetary Science
National and Kapodistrian University of Athens
2020-2024
Pasteur Hellenic Institute
2021-2024
Méditerranée Infection Foundation
2021
Max Planck Institute for Radio Astronomy
2011-2020
Max Planck Society
2006-2019
University of Maryland, College Park
2018
Tokyo Institute of Technology
2018
Institute for Space Astrophysics and Planetology
2018
California Institute of Technology
2007-2018
Goddard Space Flight Center
2008-2018
(Abridged) We have conducted a detailed investigation of the broad-band spectral properties \gamma-ray selected blazars Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months LBAS data taking period, we were able to assemble high-quality quasi-simultaneous Spectral Energy Distributions (SED) for 48 blazars.The SED these sources is similar that...
The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before start of LAT science operations, we began large-scale, fast-cadence 15 GHz radio monitoring program with 40-m telescope at Owens Valley Radio Observatory (OVRO). This 1158 northern (declination>-20 deg) sources from Candidate Blazar Survey (CGRaBS) and now encompasses over 1500 sources,...
XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to Astronomy. At time of writing XIPE in competitive phase A as fourth medium size ESA (M4). It promises reopen polarimetry window high energy Astrophysics after more than 4 decades thanks detector that efficiently exploits photoelectric effect and optics with large effective area. uniqueness time-spectrally-spatially- resolved breakthrough astrophysics fundamental physics. Indeed payload consists three Gas Pixel Detectors...
We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources this type and omitting those with steep spectra. analyse data from frequencies to X-rays, supplement these information available online catalogues literature in order cover full electromagnetic spectrum. This is largest for source. detected 90% X-rays found 17% at γ rays. Extreme variability high energies was also found, down timescales as...
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard gamma-ray bands. Our unique set has allowed us demonstrate that selection method strongly influences results, producing biases cannot be ignored. Almost all BL Lac objects have been detected by Fermi-LAT, whereas ~40% of flat-spectrum radio quasars (FSRQs) radio, X-ray selected are still below detection limit even after integrating 27 months...
Gut microbiota play a major role in digestion and energy conversion of nutrients. Antibiotics, such as avoparcin (a vancomycin analogue), probiotics, Lactobacillus species, have been used to increase weight farm animals. We tested the effect antibiotics given for infective endocarditis (IE) on gain (WG).Forty-eight adults with definite diagnosis bacterial IE (antibiotic group) were compared forty-eight age-matched controls without IE. Their body mass index (BMI) was collected at one month...
The exact location of the gamma-ray emitting region in blazars is still controversial. In order to attack this problem we present first results a cross-correlation analysis between radio (11 cm 0.8 mm wavelength, F-GAMMA program) and (0.1-300 GeV) ~ 3.5 year light curves 54 Fermi-bright blazars. We perform source stacking estimate significances chance correlations using mixed correlations. Our reveal: (i) highly significant multi-band (radio lagging gamma rays) when averaging over whole...
Background A bacterial role in the obesity pandemic has been suspected based on ingestion of probiotics that can modify gut flora. The objective our study was to determine if increased Lactobacillus sp. flora newborn broiler chicks and ducks could result weight gain increase. Methodology Female (Gallus gallus domesticus) (Anas platyrhynchos domestica) were separated into one control two experimental groups, inoculated once or twice with 4×1010 spp. per animal PBS, PBS alone. Fecal samples...
We present a detailed statistical analysis of the correlation between radio and gamma-ray emission Active Galactic Nuclei (AGN) detected by Fermi during its first year operation, with largest datasets ever used for this purpose. use both archival interferometric 8.4 GHz data (from VLA ATCA, full sample 599 sources) concurrent single-dish 15 measurements from Owens Valley Radio Observatory (OVRO, sub 199 objects). Our unprecedentedly large permits us to assess high accuracy significance...
In order to determine the location of gamma-ray emission site in blazars, we investigate time-domain relationship between their radio and emission. Light curves for brightest detected blazars from first 3 yr mission Fermi Gamma-ray Space Telescope are cross-correlated with 4 15 GHz observations Owens Valley Radio Observatory 40 m monitoring programme. The large sample long light-curve duration enable us carry out a statistically robust analysis significance cross-correlations, which is...
Background Few studies have tested the small intestine microbiota in humans, where most nutrient digestion and absorption occur. Here, our objective was to examine duodenal between obese normal volunteers using metagenomic techniques. Methodology/Principal Findings We samples from five 16S rDNA V6 pyrosequencing Illumina MiSeq deep sequencing. The predominant phyla of were Firmicutes Actinobacteria, whereas Bacteroidetes absent. Obese individuals had a significant increase anaerobic genera...
We report Fermi-LAT observations of the radio-loud AGN SBS 0846+513 (z=0.5835), optically classified as a Narrow-Line Seyfert 1 galaxy, together with new and archival radio-to-X-ray data. The source was not active at gamma-ray energies during first two years Fermi operation. A significant increase in activity observed 2010 October-2011 August. In particular strong flare 2011 June reaching an isotropic luminosity (0.1-300 GeV) 1.0x10^48 erg/s, comparable to that brightest flat spectrum radio...
We present first results on polarization swings in optical emission of blazars obtained by RoboPol, a monitoring program an unbiased sample gamma-ray bright specially designed for effective detection such events. A possible connection swing events with periods high activity gamma rays is investigated using the dataset during season operation. It was found that brightest flares tend to be located closer time rotation events, which may indication two separate mechanisms responsible rotations....
We present average R-band optopolarimetric data, as well variability parameters, from the first and second RoboPol observing season. investigate whether gamma-ray-loud gamma-ray-quiet blazars exhibit systematic differences in their optical polarization properties. find that have a systematically higher fraction (0.092) than (0.031), with hypothesis of two samples being drawn same distribution fractions rejected at 3σ level. not found any evidence this discrepancy is related to redshift...
Abstract Background/Objectives: The gut microbiota contributes to energy acquisition from food, and changes in the microbiome are associated with obesity. eating habits of Saudis much different than those Europeans, our objective was compare fecal obese normal weight French. Subjects/Methods: Illumina MiSeq deep sequencing used test 9 individuals Saudi Arabia 16 12 France. Results: Obese French possessed significantly more relative Proteobacteria ( P =0.002) Bacteroidetes =0.05) had lower...
Abstract The lower-energy peak of the spectral energy distribution blazars has commonly been ascribed to synchrotron radiation from relativistic particles in jets. Despite consensus regarding jet emission processes, particle acceleration mechanism is still debated. Here, we present first X-ray polarization observations PG 1553+113, a high-synchrotron-peak blazar observed by Imaging Polarimetry Explorer (IXPE). We detect an degree (10 ± 2)% along electric-vector position angle ψ X = 86° 8°....
Abstract We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/ γ -ray outburst, 287 ks observation (2022 November 27–30) was taken using Imaging Polarimetry Explorer (IXPE), together with contemporaneous multiwavelength observations from Neil Gehrels Swift observatory and XMM-Newton soft X-rays (0.3–10 keV), NuSTAR hard (3–70 optical Calar Alto Perkins Telescope observatories. Our data suggest that IXPE energy band is at crossover...
Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic sources, based on the Planck Early Release Compact Source Catalogue (ERCSC) simultaneous multifrequency data. The nine frequencies, from 30 to 857 GHz, complemented by set observations ranging gamma-rays. This is first extensive frequency coverage in millimetre domains an essentially complete it shows how individual shocks, each their own phase development, shape as they...
We present measurements of rotations the optical polarization blazars during second year operation RoboPol, a monitoring programme an unbiased sample gamma-ray bright specially designed for effective detection such events, and we analyse large set rotation events discovered in two years observation. investigate patterns variability parameters total flux density compare them to behaviour non-rotating state. have searched possible correlations between average polarization-plane polarization,...
We use results of our 3 yr polarimetric monitoring programme to investigate the previously suggested connection between rotations polarization plane in optical emission blazars and their gamma-ray flares GeV band. The homogeneous set 40 rotation events 24 sources detected by RoboPol is analysed together with data provided Fermi-LAT. confirm that are indeed related closest time lags these consistent zero. Amplitudes anticorrelated amplitudes flares. This presumably caused higher relativistic...
We present the results of a series radio, optical, X-ray and gamma-ray observations BL Lac object S50716+714 carried out between April 2007 January 2011. The multi-frequency were obtained using several ground space based facilities. intense optical monitoring source reveals faster repetitive variations superimposed on long-term variability trend at time scale ~350 days. Episodes fast recur scales ~ 60-70 simultaneous activity frequencies favors SSC mechanism for production high-energy...
Transmission by the oral route of Coxiella burnetii is controversial. Our objective was to evaluate dairy products in transmission Q fever. Pasteurized, unpasteurized, and thermized were tested for C. using a quantitative polymerase chain reaction specific IS1111 IS30A spacers, culturing human embryonic lung fibroblasts cells, inoculation into BALB/c mice. We 201 identified 64%. Cow milk origin more frequently positive than goat or ewe ( P = 0.006 0.0001, respectively), industrial food...
Abstract Host genetics, environment, lifestyle and proximity between hosts strongly influence the composition of gut microbiome. To investigate association dietary variables with microbiota, we used 16S rDNA sequencing to test fecal microbiome Bedouins urban Saudis compared it baboons living in close contact eating their leftovers. We also analyzed fermented dairy products commonly consumed by order impact on this population. found that microbiomes westernized had significantly lower...
We studied the radio emission from four radio-loud and gamma-ray-loud narrow-line Seyfert 1 galaxies. The goal was to investigate whether a relativistic jet is operating at source, quantify its characteristics. relied on most systematic monitoring of such system in cm mm bands which conducted with Effelsberg 100 m IRAM 30 telescopes covers longest time-baselines frequencies date. extract variability parameters compute brightness temperatures Doppler factors. powers were computed light curves...
Recent population studies have shown that the variability Doppler factors can adequately describe blazars as a population. We use flux density variations found within extensive radio multi-wavelength datasets of F-GAMMA program, total 10 frequencies from 2.64 up to 142.33 GHz, in order estimate for 58 $γ$-ray bright sources, 20 which no factor has been estimated before. employ specifically designed algorithms obtain model each flare at frequency. then identify event and track its evolution...