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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. Source

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. Source

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. Source

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. Source

Garcia J.,Harvard - Smithsonian Center for Astrophysics | Garcia J.,University of Maryland University College | Dauser T.,Erlangen Center for Astroparticle Physics | Reynolds C.S.,University of Maryland University College | And 4 more authors.
Astrophysical Journal | Year: 2013

We present a new and complete library of synthetic spectra for modeling the component of emission that is reflected from an illuminated accretion disk. The spectra were computed using an updated version of our code XILLVER that incorporates new routines and a richer atomic database. We offer in the form of a table model an extensive grid of reflection models that cover a wide range of parameters. Each individual model is characterized by the photon index Γ of the illuminating radiation, the ionization parameter ξ at the surface of the disk (i.e., the ratio of the X-ray flux to the gas density), and the iron abundance A Fe relative to the solar value. The ranges of the parameters covered are 1.2 ≤ Γ ≤ 3.4, 1 ≤ ξ ≤ 104, and 0.5 ≤ A Fe ≤ 10. These ranges capture the physical conditions typically inferred from observations of active galactic nuclei, and also stellar-mass black holes in the hard state. This library is intended for use when the thermal disk flux is faint compared to the incident power-law flux. The models are expected to provide an accurate description of the Fe K emission line, which is the crucial spectral feature used to measure black hole spin. A total of 720 reflection spectra are provided in a single FITS file (http://hea-www.cfa.harvard.edu/ ∼javier/xillver/) suitable for the analysis of X-ray observations via the atable model in XSPEC. Detailed comparisons with previous reflection models illustrate the improvements incorporated in this version of XILLVER. © 2013. The American Astronomical Society. All rights reserved.. Source

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