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Jogler T.,Kavli Institute for Particle Astrophysics and Cosmology | Jogler T.,Erlangen Center for Astroparticle Physics | Funk S.,Kavli Institute for Particle Astrophysics and Cosmology | Funk S.,Erlangen Center for Astroparticle Physics
Astrophysical Journal | Year: 2016

Supernova remnants (SNRs) are commonly believed to be the primary sources of Galactic cosmic rays. Despite intensive study of the non-thermal emission of many SNRs the identification of the accelerated particle type relies heavily on assumptions of ambient-medium parameters that are only loosely constrained. Compelling evidence of hadronic acceleration can be provided by detecting a strong roll-off in the secondary γ-ray spectrum below the production threshold energy of about 135 MeV, the so called "pion bump." Here we use five years of Fermi-Large Area Telescope data to study the spectrum above 60 MeV of the middle-aged SNR W51C. A clear break in the power-law γ-ray spectrum at is detected with significance and we show that this break is most likely associated with the energy production threshold of mesons. A high-energy break in the γ-ray spectrum at about 2.7 GeV is found with significance. The spectral index at energies beyond this second break is and closely matches the spectral index derived by the MAGIC Collaboration above 75 GeV. Therefore our analysis provides strong evidence to explain the γ-ray spectrum of W51C by a single particle population of protons with a momentum spectrum best described by a broken power law with break momentum W51C is the third middle-aged SNR that displays compelling evidence for cosmic-ray acceleration and thus strengthens the case of SNRs as the main source of Galactic cosmic rays. © 2016. The American Astronomical Society. All rights reserved.


Doroshenko V.,Institute For Astronomie Und Astrophysik | Santangelo A.,Institute For Astronomie Und Astrophysik | Kreykenbohm I.,Dr. Karl Remeis Sternwarte | Kreykenbohm I.,Erlangen Center for Astroparticle Physics | Doroshenko R.,Institute For Astronomie Und Astrophysik
Astronomy and Astrophysics | Year: 2012

We present an analysis of the spectral properties of the peculiar X-ray pulsar X Per based on INTEGRAL observations. We show that the source exhibits an unusually hard spectrum and is confidently detected by ISGRI up to more than 100 keV. We find that two distinct components may be identified in the broadband 4-200 keV spectrum of the source. We interpret these components as the result of thermal and bulk Comptonization in the vicinity of the neutron star and describe them with several semi-phenomenological models. The previously reported absorption feature at ≈30a keV is not required in the proposed scenario and therefore its physical interpretation must be taken with caution. We also investigated the timing properties of the source in the framework of existing torque theory, concluding that the observed phenomenology can be consistently explained if the magnetic field of the neutron star is ∼10 14G. © 2012 ESO.


Herold B.,Erlangen Center for Astroparticle Physics | Kalekin O.,Erlangen Center for Astroparticle Physics | Reubelt J.,Erlangen Center for Astroparticle Physics
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

The KM3NeT project aims to design and to construct at least a cubic kilometre scale neutrino telescope in the Mediterranean Sea. The main task is to instrument this deep-sea water volume with optical modules, each housing one or several photomultiplier tubes. Three-, 8- and 10-in. PMTs from ET Enterprises, Hamamatsu and MELZ-FEU have been investigated as candidates for the telescope's optical modules. Various parameters of these photomultiplier tubes have been measured in a test bench at the Erlangen Centre for Astroparticle Physics. These results are presented. © 2010 Elsevier B.V. All rights reserved.


Motz H.,Erlangen Center for Astroparticle Physics
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2010

Deep-sea neutrino telescopes consist of an array of photomultipliers to detect Cherenkov light emitted by neutrino-induced muons and particle showers in the surrounding sea water, allowing for reconstruction of the neutrino direction from position and timing of the Cherenkov photons. Since the photomultipliers are in most cases mounted on flexible structures, e.g. lines, and move with the sea current, a positioning system is required to determine the precise location of each sensor. The positioning system of the ANTARES neutrino telescope is based on acoustic triangulation using hydrophones mounted along the lines in combination with tiltmeters and compasses and provides centimetre precision alignment. For the future KM3NeT detector an Optical Module with integrated Piezo sensors for position calibration is proposed as a cost-effective solution. The performance of this system is tested with several sensors of the AMADEUS project, which is integrated in ANTARES to study the background for acoustic detection of highest energy neutrinos. © 2010 Elsevier B.V. All rights reserved.


Lahmann R.,Erlangen Center for Astroparticle Physics
Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011 | Year: 2011

The AMADEUS system is an integral part of the ANTARES neutrino telescope in theMediterranean Sea. The project aims at the investigation of techniques for acoustic neutrino detection in the deep sea. Installed at a depth of more than 2000 m, the acoustic sensors of AMADEUS are based on piezo-ceramics elements for the broad-band recording of signals with frequencies ranging up to 125kHz. AMADEUS was completed in May 2008 and comprises six "acoustic clusters", each one holding six acoustic sensors that are arranged at distances of roughly 1m from each other. The clusters are installed with inter-spacings ranging from 15m to 340 m. Acoustic data are continuously acquired and processed at a computer cluster where online filter algorithms are applied to select a high-purity sample of neutrino-like signals. In order to assess the background of neutrino-like signals in the deep sea, the characteristics of ambient noise and transient signals have been investigated. In this article, the AMADEUS system will be described and recent results will be presented.


Lahmann R.,Erlangen Center for Astroparticle Physics
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

Arrays of acoustic receivers are an integral part of present and potential future Cherenkov neutrino telescopes in the deep sea. They measure the positions of individual detector elements which vary with time as an effect of undersea currents. At the same time, the acoustic receivers can be employed for marine science purposes, in particular for monitoring the ambient noise environment and the signals emitted by the fauna of the sea. And last but not least, they can be used for studies towards acoustic detection of ultra-high-energy neutrinos. Measuring acoustic pressure pulses in huge underwater acoustic arrays with an instrumented volume of the order of 100 km3 is a promising approach for the detection of cosmic neutrinos with energies exceeding 1 EeV. Pressure signals are produced by the particle cascades that evolve when neutrinos interact with nuclei in water, and can be detected over large distances in the kilometre range. In this article, the status of acoustic detection will be reviewed and plans for the future - most notably in the context of KM3NeT - will be discussed. The connection between neutrino detection, position calibration and marine science will be illustrated. © 2013 Elsevier B.V. All rights reserved.


Kraus C.,Laurentian University | Singer A.,University of Munster | Singer A.,German Electron Synchrotron | Valerius K.,University of Munster | And 2 more authors.
European Physical Journal C | Year: 2013

The recent analysis of the normalization of reactor antineutrino data, the calibration data of solar neutrino experiments using gallium targets, and the results from the neutrino oscillation experiment MiniBooNE suggest the existence of a fourth light neutrino mass state with a mass of O (eV), which contributes to the electron neutrino with a sizable mixing angle. Since we know from measurements of the width of the Z0 resonance that there are only three active neutrinos, a fourth neutrino should be sterile (i. e., interact only via gravity). The corresponding fourth neutrino mass state should be visible as an additional kink in β-decay spectra. In this work the phase II data of the Mainz Neutrino Mass Experiment have been analyzed searching for a possible contribution of a fourth light neutrino mass state. No signature of such a fourth mass state has been found and limits on the mass and the mixing of this fourth mass state are derived. © 2013 The Author(s).


Kalekin O.,Erlangen Center for Astroparticle Physics
Nuclear Physics B - Proceedings Supplements | Year: 2012

The KM3NeT consortium has completed a Technical Design Report (TDR) for a proposed multi-cubic-kilometer sized underwater neutrino telescope that will be deployed in the Mediterranean Sea. The basic unit of an underwater neutrino telescope is the Optical Module (OM), a pyrex glass sphere capable of withstanding the great pressure of the deep sea (up to 5 km water depth) where the telescope will be deployed. The glass spheres house photomultipliers (PMTs), either a single large PMT or many smaller ones, which register the Cherenkov light arising from the secondaries of neutrino interactions. The front-end electronics, installed off-shore, will be based on an ASIC implementing a time-over-threshold signal processing. For the readout scheme, the preferred solution is a fully optical fibre-based approach with point-to-point connections between OMs and shore. All signals above an adjustable noise-rejection threshold will be transferred to shore. © 2012 Elsevier B.V.


Herold B.,Erlangen Center for Astroparticle Physics | Kalekin O.,Erlangen Center for Astroparticle Physics
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

KM3NeT is a future neutrino telescope in the Mediterranean Sea with at least 1 km3 of instrumented volume. During the current design stage, 3-, 8- and 10-in. photomultiplier tubes from Hamamatsu and ET Enterprises have been investigated as candidates for the telescope's optical modules. The most important parameters of these photomultiplier tubes, such as the time resolution, the absolute quantum efficiency of the photocathode, the inhomogeneity of the overall efficiency over the photocathode and the resulting effective photocathode area, have been measured in a test bench at the Erlangen Centre for Astroparticle Physics. These results are presented. © 2010 Elsevier B.V. All rights reserved.


Kalekin O.,Erlangen Center for Astroparticle Physics
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2010

KM3NeT is a future deep-sea research infrastructure hosting a neutrino telescope with a volume of at least one cubic kilometer to be constructed in the Mediterranean Sea. The experiment aims to detect high-energy cosmic neutrinos using a 3D array of optical modules to collect the Cherenkov light induced by charged particles in the water. Upward going muons and showers produced in neutrino interactions with the surrounding matter will allow the search and study of possible sources of extra-terrestrial neutrinos. The design of optical modules makes an important impact on the performance and cost of the KM3NeT project. Several different optical module configurations are under consideration; based on glass pressure spheres containing: a large (10 in.) hemispherical photomultiplier tube (with a multi-anode version as an option); 2531 3 in. photomultiplier tubes, or a crystal scintillator-based hybrid device (X-HPD). The features and advantages of each optical module design are discussed. © 2010 Elsevier B.V. All rights reserved.

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