Search results for "methods"
showing 10 items of 4526 documents
The 1.4 mm core of Centaurus A: First VLBI results with the South Pole Telescope
2018
Centaurus A (Cen A) is a bright radio source associated with the nearby galaxy NGC 5128 where high-resolution radio observations can probe the jet at scales of less than a light-day. The South Pole Telescope (SPT) and the Atacama Pathfinder Experiment (APEX) performed a single-baseline very-long-baseline interferometry (VLBI) observation of Cen A in January 2015 as part of VLBI receiver deployment for the SPT. We measure the correlated flux density of Cen A at a wavelength of 1.4 mm on a $\sim$7000 km (5 G$\lambda$) baseline. Ascribing this correlated flux density to the core, and with the use of a contemporaneous short-baseline flux density from a Submillimeter Array observation, we infer …
IceCube-Gen2: The Window to the Extreme Universe
2020
The observation of electromagnetic radiation from radio to $\gamma$-ray wavelengths has provided a wealth of information about the universe. However, at PeV (10$^{15}$ eV) energies and above, most of the universe is impenetrable to photons. New messengers, namely cosmic neutrinos, are needed to explore the most extreme environments of the universe where black holes, neutron stars, and stellar explosions transform gravitational energy into non-thermal cosmic rays. The discovery of cosmic neutrinos with IceCube has opened this new window on the universe. In this white paper, we present an overview of a next-generation instrument, IceCube-Gen2, which will sharpen our understanding of the proce…
Derivation of transient relativistic fluid dynamics from the Boltzmann equation
2012
In this work we present a general derivation of relativistic fluid dynamics from the Boltzmann equation using the method of moments. The main difference between our approach and the traditional 14-moment approximation is that we will not close the fluid-dynamical equations of motion by truncating the expansion of the distribution function. Instead, we keep all terms in the moment expansion. The reduction of the degrees of freedom is done by identifying the microscopic time scales of the Boltzmann equation and considering only the slowest ones. In addition, the equations of motion for the dissipative quantities are truncated according to a systematic power-counting scheme in Knudsen and inve…
The extragalactic gamma-ray sky : a view on the most powerful phenomena in the universe
2016
The gamma-ray sky provides a look into the most energetic and violent processes of the universe. In the last years, gamma-ray satellites are scanning the sky for understanding the physics governing the gamma-ray emission. A wealth of information on the physics of the gamma-ray sky has been obtained by gamma-ray satellites orbiting around the Earth. So far, roughly three thousands sources have been detected in gamma-rays, and this number is going to increase as the gamma-ray missions continue to survey the sky. The high energy sky is dominated by extragalactic objects. A large fraction of the detected sources has no obvious counterpart in catalogs at other wavelengths, leaving their nature u…
Non-thermal processes in coronae and beyond
2013
This contribution summarizes the splinter session “Non-thermal processes in coronae and beyond” held at the Cool Stars 17 workshop in Barcelona in 2012. It covers new developments in high energy non-thermal effects in the Earth's exosphere, solar and stellar flares, the diffuse emission in star forming regions and reviews the state and the challenges of the underlying atomic databases. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Summary of Working Group 4: High Energy Neutrino Telescopes
2007
The field of high-energy neutrino astronomy is rapidly developing. A number of new experiments are currently being deployed and developed. Additionally, the recent successes of TeV gamma-ray astronomy have exciting implications for future neutrino telescopes. Here we will summarize these and other issues as they were discussed in the TeV II workshop's neutrino astronomy working group.
Underground cosmic-ray experiment EMMA
2013
EMMA (Experiment with MultiMuon Array) is a new approach to study the composition of cosmic rays at the knee region (1 − 10 PeV). The array will measure the multiplicity and lateral distribution of the high-energy muon component of an air shower and its arrival direction on an event-by-event basis. The array operates in the Pyh¨asalmi Mine, Finland, at a depth of 75 metres (or 210 m.w.e) corresponding to the cut-off energy of approximately 50 GeV for vertical muons. The data recording with a partial array has started and preliminary results of the first test runs are presented. nonPeerReviewed
Numerical viscosity in simulations of the two-dimensional Kelvin-Helmholtz instability
2020
The Kelvin-Helmholtz instability serves as a simple, well-defined setup for assessing the accuracy of different numerical methods for solving the equations of hydrodynamics. We use it to extend our previous analysis of the convergence and the numerical dissipation in models of the propagation of waves and in the tearing-mode instability in magnetohydrodynamic models. To this end, we perform two-dimensional simulations with and without explicit physical viscosity at different resolutions. A comparison of the growth of the modes excited by our initial perturbations allows us to estimate the effective numerical viscosity of two spatial reconstruction schemes (fifth-order monotonicity preservin…
Study of the Planacon XP85012 photomultiplier characteristics for its use in a Cherenkov detector
2016
Main properties of the multi-anode microchannel plate photomultiplier to be used in a Cherenkov detector are discussed. The laboratory test results obtained using irradiation of the MCP-PMT photocathode by picosecond optical laser pulses with different intensities (from single photon regime to the PMT saturation conditions) are presented. peerReviewed
Performance study of the fast timing Cherenkov detector based on a microchannel plate PMT
2017
Prototype of the fast timing Cherenkov detector, applicable in high-energy collider experiments, has been developed basing on the modified Planacon XP85012 MCP-PMT and fused silica radiators. We present the reasons and description of the MCP-PMT modification, timing and amplitude characteristics of the prototype including the summary of the detector's response on particle hits at oblique angles and MCP-PMT performance at high illumination rates.