The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

J M Ryan - One of the best experts on this subject based on the ideXlab platform.

  • scintillators with silicon photomultiplier readouts for High Energy Astrophysics and heliophysics
    Proceedings of SPIE, 2014
    Co-Authors: P F Bloser, M Mcconnell, Jason S Legere, Christopher M Bancroft, J M Ryan
    Abstract:

    Space-based gamma-ray and neutron detectors face strict constraints of mass, volume, and power, and must endure harsh operating environments. Scintillator materials have a long history of successful operation under these conditions, and new materials offer greatly improved performance in terms of efficiency, time response, and Energy resolution. The use of scintillators in space remains constrained, however, by the mass, volume, and fragility of the associated light readout device, typically a vacuum photomultiplier tube (PMT). Recently developed silicon photomultipliers (SiPMs) offer gains and efficiencies similar to those of PMTs, but with greatly reduced mass and volume, High ruggedness, and no High-voltage requirements. We have therefore been investigating the use of SiPM readouts for scintillator gamma-ray and neutron detectors, with an emphasis on their suitability for space-based instruments for Astrophysics and heliophysics. We present preliminary radiation hardness tests of two promising SiPM devices, and describe two concepts for SiPM-based instruments: an advanced scintillator-based Compton telescope, and a double-scatter neutron telescope suitable for measuring fast solar and magnetospheric neutrons. Supporting laboratory measurements are presented to demonstrate the feasibility of these telescope concepts.

  • status and prospects for polarimetry in High Energy Astrophysics
    New Astronomy Reviews, 2004
    Co-Authors: M Mcconnell, J M Ryan
    Abstract:

    Abstract The recent detection of linear polarization from GRB120206 has piqued the interest of the community in this relatively unexplored avenue of research. Here, we review the current status and prospects for polarimetry at hard X-ray and soft γ-ray energies. After reviewing the basic principles of making polarization measurements at these energies, we give an overview of the most recent results and present a brief survey of current and planned experiments that are capable of making polarization measurements in the Energy range between 30 keV and 30 MeV.

F Aharonian - One of the best experts on this subject based on the ideXlab platform.

  • a radiation transfer model for the milky way i radiation fields and application to High Energy Astrophysics
    Monthly Notices of the Royal Astronomical Society, 2017
    Co-Authors: Cristina Popescu, R Yang, Richard J Tuffs, G Natale, M T Rushton, F Aharonian
    Abstract:

    We present a solution for the ultraviolet (UV) - submillimeter (submm) interstellar radiation fields (ISRFs) of the Milky Way, derived from modelling COBE, IRAS and Planck maps of the all-sky emission in the near-, mid-, far-infrared and submm. The analysis uses the axisymmetric radiative transfer (RT) model that we have previously implemented to model the panchromatic spectral Energy distributions (SEDs) of star forming galaxies in the nearby universe, but with a new methodology allowing for optimisation of the radial and vertical geometry of stellar emissivity and dust opacity, as deduced from the Highly resolved emission seen from the vantage point of the Sun. As such, this is the first self-consistent model of the broad-band continuum emission from the Milky Way. In this paper, we present model predictions for the spatially integrated SED of the Milky Way as seen from the Sun, showing good agreement with the data, and give a detailed description of the solutions for the distribution of ISRFs, as well as their physical origin, throughout the volume of the galaxy. We explore how the spatial and spectral distribution of our new predictions for the ISRF in the Milky Way affects the amplitude and spectral distribution of the gamma-rays produced via Inverse Compton scattering for cosmic ray electrons situated at different positions in the galaxy, as well as the attenuation of the gamma-rays due to interactions of the gamma-ray photons with photons of the ISRF. We also compare and contrast our solutions for the ISRF with those incorporated in the GALPROP package used for modelling the High Energy emission from cosmic rays in the Milky Way.

  • High Energy Astrophysics with ground based gamma ray detectors
    Reports on Progress in Physics, 2008
    Co-Authors: F Aharonian, J H Buckley, T Kifune, G Sinnis
    Abstract:

    Recent advances in ground-based gamma ray astronomy have led to the discovery of more than 70 sources of very High Energy (E? ? 100?GeV) gamma rays, falling into a number of source populations including pulsar wind nebulae, shell type supernova remnants, Wolf-Rayet stars, giant molecular clouds, binary systems, the Galactic Center, active galactic nuclei and 'dark' (yet unidentified) galactic objects. We summarize the history of TeV gamma ray astronomy up to the current status of the field including a description of experimental techniques and Highlight recent astrophysical results. We also discuss the potential of ground-based gamma ray astronomy for future discoveries and describe possible directions for future instrumental developments.

  • very High Energy cosmic gamma radiation a crucial window on the extreme universe
    2004
    Co-Authors: F Aharonian
    Abstract:

    Gamma ray astronomy, the branch of High Energy Astrophysics that studies the sky in energetic γ-ray photons, is destined to play a crucial role in the exploration of nonthermal phenomena in the Universe in their most extreme and violent forms. The great potential of this discipline offers impressive coverage of many “hot topics” of modern Astrophysics and cosmology, such as the origin of galactic and extragalactic cosmic rays, particle acceleration and radiation processes under extreme astrophysical conditions, and the search for dark matter. The recent observational results and exciting theoretical predictions provide a strong rationale for a deep study of cosmic radiation with forthcoming satellite-borne and ground-based detectors in the so-called very High Energy domain of the electromagnetic spectrum above 1010 eV.This invaluable book presents the motivations and Highlights the principal objectives of the field, as well as demonstrates its intrinsic links to other branches of High Energy Astrophysics. Preference is given to three topical areas: (i) origin of cosmic rays; (ii) physics and Astrophysics of relativistic jets; (iii) observational gamma ray cosmology. Also, an essential part of the book is devoted to the discussion of the principal mechanisms of production and absorption of energetic γ-rays in different astrophysical environments, as well as to the description of the detection methods of High Energy cosmic γ-radiation.

M Mcconnell - One of the best experts on this subject based on the ideXlab platform.

  • scintillators with silicon photomultiplier readouts for High Energy Astrophysics and heliophysics
    Proceedings of SPIE, 2014
    Co-Authors: P F Bloser, M Mcconnell, Jason S Legere, Christopher M Bancroft, J M Ryan
    Abstract:

    Space-based gamma-ray and neutron detectors face strict constraints of mass, volume, and power, and must endure harsh operating environments. Scintillator materials have a long history of successful operation under these conditions, and new materials offer greatly improved performance in terms of efficiency, time response, and Energy resolution. The use of scintillators in space remains constrained, however, by the mass, volume, and fragility of the associated light readout device, typically a vacuum photomultiplier tube (PMT). Recently developed silicon photomultipliers (SiPMs) offer gains and efficiencies similar to those of PMTs, but with greatly reduced mass and volume, High ruggedness, and no High-voltage requirements. We have therefore been investigating the use of SiPM readouts for scintillator gamma-ray and neutron detectors, with an emphasis on their suitability for space-based instruments for Astrophysics and heliophysics. We present preliminary radiation hardness tests of two promising SiPM devices, and describe two concepts for SiPM-based instruments: an advanced scintillator-based Compton telescope, and a double-scatter neutron telescope suitable for measuring fast solar and magnetospheric neutrons. Supporting laboratory measurements are presented to demonstrate the feasibility of these telescope concepts.

  • status and prospects for polarimetry in High Energy Astrophysics
    New Astronomy Reviews, 2004
    Co-Authors: M Mcconnell, J M Ryan
    Abstract:

    Abstract The recent detection of linear polarization from GRB120206 has piqued the interest of the community in this relatively unexplored avenue of research. Here, we review the current status and prospects for polarimetry at hard X-ray and soft γ-ray energies. After reviewing the basic principles of making polarization measurements at these energies, we give an overview of the most recent results and present a brief survey of current and planned experiments that are capable of making polarization measurements in the Energy range between 30 keV and 30 MeV.

T Louge - One of the best experts on this subject based on the ideXlab platform.

  • gammalib and ctools a software framework for the analysis of astronomical gamma ray data
    Astronomy and Astrophysics, 2016
    Co-Authors: J Knodlseder, M Mayer, C Deil, J B Cayrou, E Owen, N Kelleyhoskins, C C Lu, R Buehler, F Forest, T Louge
    Abstract:

    The field of gamma-ray astronomy has seen important progress during the last decade, yet to date no common software framework has been developed for the scientific analysis of gamma-ray telescope data. We propose to fill this gap by means of the GammaLib software, a generic library that we have developed to support the analysis of gamma-ray event data. GammaLib was written in C++ and all functionality is available in Python through an extension module. Based on this framework we have developed the ctools software package, a suite of software tools that enables flexible workflows to be built for the analysis of Imaging Air Cherenkov Telescope event data. The ctools are inspired by science analysis software available for existing High-Energy astronomy instruments, and they follow the modular ftools model developed by the High Energy Astrophysics Science Archive Research Center. The ctools were written in Python and C++, and can be either used from the command line via shell scripts or directly from Python. In this paper we present the GammaLib and ctools software versions 1.0 that were released at the end of 2015. GammaLib and ctools are ready for the science analysis of Imaging Air Cherenkov Telescope event data, and also support the analysis of Fermi -LAT data and the exploitation of the COMPTEL legacy data archive. We propose using ctools as the science tools software for the Cherenkov Telescope Array Observatory.

  • gammalib and ctools a software framework for the analysis of astronomical gamma ray data
    arXiv: Instrumentation and Methods for Astrophysics, 2016
    Co-Authors: J Knodlseder, M Mayer, C Deil, J B Cayrou, E Owen, N Kelleyhoskins, C C Lu, R Buehler, F Forest, T Louge
    Abstract:

    The field of gamma-ray astronomy has seen important progress during the last decade, yet there exists so far no common software framework for the scientific analysis of gamma-ray telescope data. We propose to fill this gap by means of the GammaLib software, a generic library that we have developed to support the analysis of gamma-ray event data. GammaLib has been written in C++ and all functionality is available in Python through an extension module. On top of this framework we have developed the ctools software package, a suite of software tools that enables building of flexible workflows for the analysis of Imaging Air Cherenkov Telescope event data. The ctools are inspired by science analysis software available for existing High-Energy astronomy instruments, and they follow the modular ftools model developed by the High Energy Astrophysics Science Archive Research Center. The ctools have been written in Python and C++, and can be either used from the command line, via shell scripts, or directly from Python. In this paper we present the GammaLib and ctools software versions 1.0 that have been released end of 2015. GammaLib and ctools are ready for the science analysis of Imaging Air Cherenkov Telescope event data, and also support the analysis of Fermi-LAT data and the exploitation of the COMPTEL legacy data archive. We propose to use ctools as the Science Tools software for the Cherenkov Telescope Array Observatory.

Giorgio Galanti - One of the best experts on this subject based on the ideXlab platform.

  • importance of axion like particles for very High Energy Astrophysics
    Physical Review D, 2011
    Co-Authors: Marco Roncadelli, Alessandro De Angelis, Giorgio Galanti
    Abstract:

    Several extensions ol the Standard Model predict the existence ol Axion-Like Particles (ALPs), very light spin-zero bosons with a two-photon coupling. ALPs can give rise to observable effects in very-High-Energy Astrophysics. Above roughly 100 GeV the horizon of the observable Universe progressively shrinks as the Energy increases, due to scattering of beam photons off background photons in the optical and infrared bands, which produces e+ e− pairs. In the presence of large-scale magnetic fields photons emitted by a blazar can oscillate into ALPs on the way to us and back into photons before reaching the Earth. Since ALPs do not interact with background photons, the effective mean free path of beam photons increases, enhancing the photon survival probability. While the absorption probability increases with Energy, photon-ALP oscillations are Energy-independent, and so the survival probability increases with Energy compared to standard expectations. We have performed a systematic analysis of this effect, interpreting the present data on very-High-Energy photons from blazars. Our predictions can be tested with presently operating Cherenkov Telescopes like H.E.S.S., MAGIC, VERITAS and CANGAROO III as well as with detectors like ARGO-YBJ and MILAGRO and with the planned Cherenkov Telescope Array and the HAWC γ-ray observatory. ALPs with the right properties to produce the above effects can possibly be discovered by the GammeV experiment at FERMILAB and surely by the planned photon regeneration experiment ALPS at DESY.