A5063183504- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Historical Geography and Cartography
- Computational Physics and Python Applications
- Geophysics and Gravity Measurements
- Historical Astronomy and Related Studies
- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Planetary Science and Exploration
- Space exploration and regulation
- Nuclear Physics and Applications
- Spacecraft Design and Technology
- Space Satellite Systems and Control
- Particle physics theoretical and experimental studies
- Pulsars and Gravitational Waves Research
- Particle Detector Development and Performance
Fraunhofer Institute for High Frequency Physics and Radar Techniques
2018-2025
Max Planck Institute for Radio Astronomy
2012-2019
Max Planck Society
2013-2019
Boston University
2016
W.M. Keck Observatory
2016
Institut de Radioastronomie Millimétrique
2016
Center for Astrophysics Harvard & Smithsonian
2016
Aristotle University of Thessaloniki
2008
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...
Context. The γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec “jet-wobbling”, high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane.
To fully exploit the scientific potential of Fermi mission, we initiated F-GAMMA program. Between 2007 and 2015 it was prime provider complementary multi-frequency monitoring in radio regime. We quantify variability gamma-ray blazars. investigate its dependence on source class examine whether is related to loudness. Finally, assess validity a putative correlation between two bands. The monitored monthly sample about 60 sources at up twelve frequencies 2.64 228.39 GHz. perform time series...
The narrow-line Seyfert 1 galaxy SBS 0846+513 was first detected by the Large Area Telescope (LAT) on-board Fermi in 2011 June-July when it underwent a period of flaring activity. Since then, as continues to accumulate data on this source, its flux has been monitored daily basis. Two further gamma-ray episodes from were observed 2012 May and August, reaching peak integrated above 100 MeV (50+/-12)x10^-8 ph/cm^2/s, (73+/-14)x10^-8 ph/cm^2/s 24 August 7, respectively. Three outbursts at 15 GHz...
Context. Blazars are among the most energetic objects in Universe. In 2008 August, Fermi/LAT detected blazar PKS 1502+106, which showed a rapid and strong γ-ray outburst followed by high variable flux over next months. This activity at energies triggered an intensive multi-wavelength campaign that also covered radio, optical, UV, X-ray bands, indicating flare was accompanied simultaneous optical/UV/X-rays delayed radio bands.
In today’s world, where near-Earth space constitutes an increasingly congested andcontested theater of economic, political, and military activities for the growing numberof space-faring nations, significance actionable situational awareness cannot beoverstated[...]
We present follow-up spectroscopy and photometry of 11 post-common envelope binary (PCEB) candidates identified from multiple Sloan Digital Sky Survey (SDSS) in an earlier paper. Radial velocity measurements using the Na i λλ8183.27, 8194.81 absorption doublet were performed for nine these systems provided six orbital periods range Porb= 2.7– 17.4 h. Three PCEB did not show significant radial variations data, we discuss implications use SDSS alone to identify PCEBs. Differential confirmed...
Near-Eddington accretion rates onto low-mass black holes are thought to be a prime driver of the multi-wavelength properties narrow-line Seyfert 1 (NLS1) population active galactic nuclei (AGNs). Orientation effects have repeatedly been considered as another important factor involved, but detailed studies hampered by lack measured viewing angles towards this type AGN. Here we present multi-epoch, 15 GHz VLBA images (MOJAVE program) radio-loud and Fermi/LAT-detected NLS1 galaxy 1H 0323+342....
The advent of the Fermi-GST with its unprecedented capability to monitor entire 4 pi sky within less than 2-3 hours, introduced new standard in time domain gamma-ray astronomy. To explore this avenue extragalactic physics F-GAMMA programme undertook task conducting nearly monthly, broadband radio monitoring selected blazars from January 2007 2015. In work we release all light curves at 2.64, 4.85, 8.35, 10.45, 14.6, 23.05, 32, and 43 GHz present first order derivative data products after...
Context. The origin of blazar variability, as seen from radio up to γ rays, is still a heavily debated matter, and broadband flares offer unique testbed for developing better understanding these extreme objects. One energetic outbursts was detected by Fermi/LAT in 2008 the PKS 1502+106. outburst observed rays down frequencies.
We present a pipeline that allows recovering reliable information for all four Stokes parameters with high accuracy. Its novelty relies on the treatment of instrumental effects already prior to computation contrary conventional methods, such as M\"uller matrix one. The linear polarization is corrected across whole telescope beam and significant $Q$ $U$ can be recovered even when recorded signals are severely corrupted. accuracy we reach in terms degree order 0.1-0.2 %. angles determined an...
During deorbiting, be it natural orbital decay or otherwise (e.g. self-disposal active debris removal), precise knowledge of the condition target is critical importance. The Tracking and Imaging Radar (TIRA) an instrument that possesses ability to accurately determine satellite space orbits while also generating detailed radar images them. We present recent results from characterization deorbiting satellites employing TIRA. Drawing examples events (Tiangong-1, Soyuz 2.1v R/B), (Tiangong-2)...
Aims. Radio-loud narrow-line type 1 galaxies provide us with a fresh look at the blazar phenomenon, causes of radio loudness, and physics jet formation. We present multi-wavelength study radio-loud quasar RX J2314.9+2243, which exhibits some remarkable properties. It is among few galaxies, tentative γ-ray detection, luminous in infrared, shows an exceptionally broad blueshifted [OIII]λ5007 emission-line component.
The use of near-Earth space has grown dramatically during the last decades, resulting in thousands active and inactive satellites a huge amount debris. To observe monitor environment, radar systems play major role as they can be operated at any time under weather conditions. Tracking Imaging Radar (TIRA) is one largest observation radars world. It consists 34m Cassegrain antenna, precise tracking radar, high-resolution imaging radar. Since 1990s, TIRA contributes to field domain awareness by...
We present a multi-frequency, dense radio monitoring program of the blazar OJ287 using 100m Effelsberg telescope. analyze evolution in total flux density, linear and circular polarization to study jet structure its magnetic field geometry. The density is measured at nine bands from 2.64 GHz 43 GHz, parameters between 10.45 4.85 8.35 GHz. mean cadence 10 days. Between MJD 57370 57785, showed flaring activity complex behavior. EVPA large clockwise (CW) rotation by ~340$^{\circ}$ with rate...
In March 2018, Mukherjee (2018) reported the detection by VERITAS of very-high-energy emission (VHE; > 100 GeV) from 3C 264. This is sixth, and second most distant, radio galaxy ever detected in TeV regime. this article we present a X-ray analysis jet We determine main physical parameters parsec-scale flow explore implications inferred kinematic structure for radiative models gamma-ray emitting jet. The data set comprised VLBI observations at 15 GHz MOJAVE program, cover time period ~2...
In September 2012, the high-synchrotron-peaked (HSP) blazar Markarian 421 underwent a rapid wideband radio flare, reaching nearly twice brightest level observed in centimeter band over three decades of monitoring. response to this event we carried out five epoch centimeter- millimeter-band multifrequency Very Long Baseline Array (VLBA) campaign investigate aftermath emission event. Rapid variations are unprecedented object and surprising an HSP BL Lac object. 15 GHz flux density increased...
Abstract Black holes, anywhere in the stellar-mass to supermassive range, are often associated with relativistic jets. Models suggest that jet production may be a universal process common all black hole systems regardless of their mass. Although many cases observations support such hypotheses for microquasars and Seyfert galaxies, little is known regarding whether boosted blazar jets also comply scaling laws. We use uniquely rich multi-wavelength radio light curves from F-GAMMA program most...