Search

The stratified two-sided jet of Cygnus A. Acceleration and collimation

2015

High-resolution Very-Long-Baseline Interferometry observations of relativistic jets are essential to constrain fundamental parameters of jet formation models. At a distance of 249 Mpc, Cygnus A is a unique target for such studies, being the only Fanaroff-Riley Class II radio galaxy for which a detailed sub-parsec scale imaging of the base of both jet and counter-jet can be obtained. Observing at millimeter wavelengths unveils those regions which appear self-absorbed at longer wavelengths and enables an extremely sharp view towards the nucleus to be obtained. We performed 7 mm Global VLBI observations, achieving ultra-high resolution imaging on scales down to 90 $\mu$as. This resolution corr…

AstrofísicaPhysicsHigh Energy Astrophysical Phenomena (astro-ph.HE)Jet (fluid)010504 meteorology & atmospheric sciencesRadio galaxyAstrophysics::High Energy Astrophysical PhenomenaFOS: Physical sciencesAstronomy and AstrophysicsAcceleration (differential geometry)Astrophysics01 natural sciencesBase (group theory)WavelengthAstrophysical jetSpace and Planetary Science0103 physical sciencesAstronomiaCygnus AAstrophysics - High Energy Astrophysical Phenomena010303 astronomy & astrophysicsSchwarzschild radius0105 earth and related environmental sciences

researchProduct

Magnetic Ergostars, Jet Formation and Gamma-Ray Bursts: Ergoregions versus Horizons

2020

We perform the first fully general relativistic, magnetohydrodynamic simulations of dynamically stable hypermassive neutron stars with and without ergoregions to assess the impact of ergoregions on launching magnetically--driven outflows. The hypermassive neutron stars are modeled by a compressible and causal equation of state and are initially endowed with a dipolar magnetic field extending from the stellar interior into its exterior. We find that, after a few Alfv\'en times, magnetic field lines in the ergostar (star that contains ergoregions) and the normal star have been tightly wound in both cases into a helical funnel within which matter begins to flow outward. The maximum Lorentz fac…

AstrofísicaStar (game theory)Astrophysics::High Energy Astrophysical PhenomenaFOS: Physical sciencesGeneral Relativity and Quantum Cosmology (gr-qc)AstrophysicsAstrophysics::Cosmology and Extragalactic Astrophysics01 natural sciencesGeneral Relativity and Quantum CosmologyLuminositysymbols.namesakeAstrophysical jet0103 physical sciencesAstrophysics::Solar and Stellar Astrophysics010303 astronomy & astrophysicsAstrophysics::Galaxy AstrophysicsHigh Energy Astrophysical Phenomena (astro-ph.HE)Physics010308 nuclear & particles physicsEquation of state (cosmology)Black holeLorentz factorNeutron starsymbolsAstrophysics::Earth and Planetary AstrophysicsGamma-ray burstAstrophysics - High Energy Astrophysical Phenomena

researchProduct

The influence of circumnuclear environment on the radio emission from TDE jets

2016

Dozens of stellar tidal disruption events (TDEs) have been identified at optical, UV and X-ray wavelengths. A small fraction of these, most notably Swift J1644+57, produce radio synchrotron emission, consistent with a powerful, relativistic jet shocking the surrounding circumnuclear gas. The dearth of similar non-thermal radio emission in the majority of TDEs may imply that powerful jet formation is intrinsically rare, or that the conditions in galactic nuclei are typically unfavorable for producing a detectable signal. Here we explore the latter possibility by constraining the radial profile of the gas density encountered by a TDE jet using a one-dimensional model for the circumnuclear med…

AstrofísicaStellar populationAstrophysics::High Energy Astrophysical PhenomenaFOS: Physical sciencesAstrophysicsAstrophysics::Cosmology and Extragalactic Astrophysics01 natural sciences7. Clean energylaw.inventionLuminositylaw0103 physical sciences010306 general physics010303 astronomy & astrophysicsAstrophysics::Galaxy AstrophysicsPhysicsHigh Energy Astrophysical Phenomena (astro-ph.HE)Jet (fluid)Star formationAstronomyAstronomy and AstrophysicsRadiusLight curveSynchrotronWavelength13. Climate actionSpace and Planetary ScienceAstronomiaAstrophysics - High Energy Astrophysical Phenomena

researchProduct

Discovery of off-axis jet structure of TeV blazar Mrk 501 with mm-VLBI

2016

Context. High-resolution millimeter wave very-long-baseline interferometry (mm-VLBI) is an ideal tool for probing the structure at the base of extragalactic jets in detail. The TeV blazar Mrk 501 is one of the best targets among BL Lac objects for studying the nature of off-axis jet structures because it shows different jet position angles at different scales. Aims. The aim of this study is to investigate the properties of the off-axis jet structure through high-resolution mm-VLBI images at the jet base and physical parameters such as kinematics, flux densities, and spectral indices. Methods. We performed Very Long Baseline Array (VLBA) observations over six epochs from 2012 February to 201…

Astrofísicaactive [Galaxies]010504 meteorology & atmospheric sciencesAstrophysics::High Energy Astrophysical PhenomenaFOS: Physical sciencesFluxContext (language use)galaxies [Radio continuum]Astrophysics::Cosmology and Extragalactic AstrophysicsAstrophysics01 natural sciencesRadio continuum: galaxiesindividual: Markarian 501 [BL Lacertae objects]0103 physical sciencesVery-long-baseline interferometryBlazar010303 astronomy & astrophysicsAstrophysics::Galaxy AstrophysicsVery Long Baseline Array0105 earth and related environmental sciencesHigh Energy Astrophysical Phenomena (astro-ph.HE)PhysicsJet (fluid)Spectral indexBL Lacertae objects: individual: Markarian 501 galaxies: active galaxies: jets radio continuum: galaxiesAstrophysics::Instrumentation and Methods for AstrophysicsAstronomy and AstrophysicsGalaxies: activeAstrophysics - Astrophysics of GalaxiesBL Lacertae objects: individual: Markarian 501Galaxies: jetsSpace and Planetary ScienceAstrophysics of Galaxies (astro-ph.GA)Astronomiajets [Galaxies]MillimeterAstrophysics - High Energy Astrophysical PhenomenaAstronomy & Astrophysics

researchProduct

Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating

2017

We describe a new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas. The discussed ‘three-ion’ scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. We demonstrate the potential of the method on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of 3He ions to high energies in dedicated hydrogen–deuterium mixtures.…

Astrophysical plasmasTokamakradio-frequency heatingCyclotronJoint European TorusPlasma heatingGeneral Physics and AstronomyFREQUENCY114 Physical sciences01 natural sciences7. Clean energyMagnetically confined plasmas010305 fluids & plasmaslaw.inventionIonPHYSICSPhysics and Astronomy (all)FUSIONMODE CONVERSIONlawPhysics::Plasma Physics0103 physical sciencesDielectric heating010306 general physicsPhysics[PHYS]Physics [physics]ta114Solar flare:Física [Àrees temàtiques de la UPC]Plasma dynamicsmulti-ion plasmasSettore FIS/01 - Fisica SperimentaleMagnetic confinement fusionPlasmaHE-3-RICH SOLAR-FLARESTècniques de plasmaJETCYCLOTRON RANGETOKAMAKPhysics::Space PhysicsAtomic physicsHE-3-RICH SOLAR-FLARES; MODE CONVERSION; CYCLOTRON RANGE; FUSION; JET; FREQUENCY; TOKAMAK; PHYSICS

researchProduct