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  • 1
    Monographie ausleihbar
    Monographie ausleihbar
    The strongest magnetic fields in the universe (2016)
    New York NY [u.a.] : Springer
    Dazugehörige Bände
    Details Verfügbarkeit
    Signatur: 5/M 18.91370
    In: Space siences series of ISSI
    Beschreibung / Inhaltsverzeichnis: Foreword -- part 1. Introduction -- Magnetic fields at largest universal strengths : overview -- Physics in very strong magnetic fields : an introduction -- part 2. Magnetic fields in stars -- Observations of strong magnetic fields in nondegenerate stars -- Magnetic field generation in stars -- Magnetic white dwarfs -- part 3. Neutron stars -- Neutron stars : thermal emitters -- Radio pulsars -- Neutron stars : cooling and transport -- Magnetic fields of neutron stars in X-ray binaries -- Magnetars : properties, origin, and evolution -- part 4. Accretion, winds, jets -- Accretion and outflows from magnetized stars -- Pulsar wind nebulae -- Disks and jets : gravity, rotation, and magnetic fields -- part 5. Physical processes -- gamma ray bursts as sources of strong magnetic fields -- Relativistic shocks, particle acceleration, and magnetization -- Relativistic magnetic reconnection and Its astrophysical applications
    Materialart: Monographie ausleihbar
    Seiten: 583 Seiten , Illustrationen
    ISBN: 1493935496 , 9781493935499 , 9781493935505 (electronic)
    Serie: Space sciences series of ISSI 54
    Klassifikation:
    Geomagnetismus u. Geoelektromagnetik
    Sprache: Englisch
    Standort: Lesesaal
    Zweigbibliothek: GFZ Bibliothek
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    Hybrid CdZnO/GaN quantum-well light emitting diodes (2008)
    American Institute of Physics
    Details
    Publikationsdatum: 2008-11-01
    Print ISSN: 0021-8979
    Digitale ISSN: 1089-7550
    Thema: Physik
    Publiziert von American Institute of Physics
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  • 3
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    High-energy characteristics of the accretion-powered millisecond pulsar IGR J17591−2342 during its 2018 outburst (2020)
    EDP Sciences
    Details
    Publikationsdatum: 2020-09-01
    Beschreibung: IGR J17591−2342 is an accreting millisecond X-ray pulsar, discovered with INTEGRAL, which went into outburst around July 21, 2018. To better understand the physics acting in these systems during the outburst episode, we performed detailed temporal-, timing-, and spectral analyses across the 0.3–300 keV band using data from NICER, XMM-Newton, NuSTAR, and INTEGRAL. The hard X-ray 20–60 keV outburst profile covering ∼85 days is composed of four flares. Over the course of the maximum of the last flare, we discovered a type-I thermonuclear burst in INTEGRAL JEM-X data, posing constraints on the source distance. We derived a distance of 7.6 ± 0.7 kpc, adopting Eddington-limited photospheric radius expansion and assuming anisotropic emission. In the timing analysis, using all NICER 1–10 keV monitoring data, we observed a rather complex set of behaviours starting with a spin-up period (MJD 58345–58364), followed by a frequency drop (MJD 58364–58370), an episode of constant frequency (MJD 58370–58383), concluded by irregular behaviour till the end of the outburst. The 1–50 keV phase distributions of the pulsed emission, detected up to ∼120 keV using INTEGRAL ISGRI data, was decomposed in three Fourier harmonics showing that the pulsed fraction of the fundamental increases from ∼10% to ∼17% going from ∼1.5 to ∼4 keV, while the harder photons arrive earlier than the soft photons for energies ≲10 keV. The total emission spectrum of IGR J17591−2342 across the 0.3–150 keV band could adequately be fitted in terms of an absorbed COMPPS model yielding as best fit parameters a column density of NH = (2.09 ± 0.05) × 1022 cm−2, a blackbody seed photon temperature kTbb, seed of 0.64 ± 0.02 keV, electron temperature kTe = 38.8 ± 1.2 keV and Thomson optical depth τT = 1.59 ± 0.04. The fit normalisation results in an emission area radius of 11.3 ± 0.5 km adopting a distance of 7.6 kpc. Finally, the results are discussed within the framework of accretion physics- and X-ray thermonuclear burst theory.
    Print ISSN: 0004-6361
    Digitale ISSN: 1432-0746
    Thema: Physik
    Publiziert von EDP Sciences
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  • 4
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    Stochastic Resonance Mechanism in Aerosol Index Dynamics (2002)
    American Physical Society
    Details
    Publikationsdatum: 2002-08-30
    Print ISSN: 0031-9007
    Digitale ISSN: 1079-7114
    Thema: Physik
    Publiziert von American Physical Society
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  • 5
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    Water-level oscillations in the Adriatic Sea as coherent self-oscillations inferred by independent component analysis (2011)
    Elsevier
    Details
    Publikationsdatum: 2011-12-01
    Print ISSN: 0079-6611
    Digitale ISSN: 1873-4472
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Elsevier
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  • 6
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    On the nature of the hard X-ray sources SWIFT J1907.3-2050, IGR J12123-5802 and IGR J19552+0044 (2013)
    Oxford University Press
    Details
    Publikationsdatum: 2013-10-12
    Beschreibung: The INTEGRAL and Swift hard X-ray surveys have identified a large number of new sources, among which many are proposed as Cataclysmic Variables (CVs). Here, we present the first detailed study of three X-ray-selected CVs, Swift J1907.3–2050, IGR J12123–5802 and IGR J19552+0044 based on XMM–Newton , Suzaku , Swift observations and ground-based optical and archival (near-IR) nIR/IR data. Swift J1907.3–2050 is highly variable from hours to months–years at all wavelengths. No coherent X-ray pulses are detected but rather transient features. The X-ray spectrum reveals a multitemperature optically thin plasma absorbed by complex neutral material and a soft blackbody component arising from a small area. These characteristics are remarkably similar to those observed in magnetic CVs. A supra-solar abundance of nitrogen could arise from nuclear processed material from the donor star. Swift J1907.3–2050 could be a peculiar magnetic CV with the second longest (20.82 h) binary period. IGR J12123–5802 is variable in the X-rays on a time-scale of 7.6 h. No coherent pulsations are detected, but its spectral characteristics suggest that it could be a magnetic CV of the Intermediate Polar (IP) type. IGR J19552+0044 shows two X-ray periods, ~1.38 h and ~1.69 h and an X-ray spectrum characterized by a multitemperature plasma with little absorption. We derive a low accretion rate, consistent with a CV below the orbital period gap. Its peculiar nIR/IR spectrum suggests a contribution from cyclotron emission. It could either be a pre-polar or an IP with the lowest degree of asynchronism.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
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  • 7
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    Statistical analysis of the volcano seismicity during the 2007 crisis of Stromboli, Italy (2011)
    Wiley
    Details
    Publikationsdatum: 2011-09-29
    Beschreibung: We analyze the volcano seismicity recorded during the pre- and co-eruptive regimes of the 2007 effusive crisis at Stromboli volcano (Italy). Data-set is composed of the continuous recordings of a three-component broad-band seismometer and of a Sacks-Evertson strainmeter. Starting from the characterization of the non effusive phase as a stationary state of equilibrium, we investigate the effusive phase as a non-equilibrium state. A statistical analysis reveals that the explosion occurrence is always driven by a nearly Poissonian process, as for the standard activity, even during the effusive phase, with the only difference in shortening the inter-times. Explosion-quake amplitudes are lognormally distributed until the effusive phase, becoming then broader. This indicates that many scales are involved. A slightly different process can be advocated for the swarms of the explosions occurring during the effusive phase. This suggests that the dynamics of the exsolution and/or aggregation of the gas slugs should differ from the nucleation mechanism responsible of the standard Strombolian activity. The pre-eruptive regime is characterized by a very long deformative signal that appears as a transient oscillating signal with a period of about three days that modulates the explosion amplitudes. In a conceptual vibrating cavities model, it is related to a chocking phenomenon induced by magma injection, which in turn leads to the effusion.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 8
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    Swift J2218.4+1925: a new hard-X-ray-selected polar observed with XMM-Newton (2014)
    Oxford University Press
    Details
    Publikationsdatum: 2014-10-12
    Beschreibung: Swift J2218.4+1925, a hard-X-ray source detected by Swift Burst Alert Telescope (BAT), has been proposed as a candidate magnetic cataclysmic variable of the polar type from optical spectroscopy. Using XMM–Newton we perform detailed timing and spectral analysis with simultaneous X-ray (0.3–10 keV) and optical B -band data. We complement the spectral study with archival hard-X-ray (14–70 keV) spectra collected by Swift BAT as well as with optical, near and mid-infrared photometry from Sloan Digital Sky Survey, Two-Micron All Sky Survey and Wide-field Infrared Survey Explorer archive, respectively. A strong periodic X-ray signal at 2.16 h, fully consistent with the recently determined spectroscopic orbital period, adds Swift J2218.4+1925 to the small group of hard-X-ray polars and locates it at the low edge of the orbital period gap. The X-ray pulse profile shows the typical bright and faint phases seen in polars, that last ~70 and ~30 per cent of the orbit, respectively. A pronounced dip centred on the bright phase is also detected. It is stronger at lower energies and is mainly produced by photoelectric absorption. A binary inclination i  ~ 40°–50° and a magnetic colatitude β ~ 55°–64° are estimated. The source appears to accrete over a large area ~24° wide. A multitemperature optically thin emission with complex absorption well describes the broad-band (0.3–70 keV) spectrum, with no signs of a soft X-ray blackbody component. The spectral shape strongly varies with the source rotation reaching plasma temperatures up to 55 keV, hardening at the dip and being softer during the faint phase (~7 keV). We also find the first indication of an absorption edge due to a warm absorber in a polar. Indication of overabundance of neon is found in the Reflection Grating Spectrometer (RGS) spectra. The UV to mid-IR spectral energy distribution reveals an excess in the near and mid-IR, likely due to low cyclotron harmonics. We further estimate a white dwarf mass of 0.97 M and a distance of 230–250 pc.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
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  • 9
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    Multiwavelength observations of the black hole transient Swift J1745-26 during the outburst decay (2014)
    Oxford University Press
    Details
    Publikationsdatum: 2014-10-12
    Beschreibung: We characterized the broad-band X-ray spectra of Swift J1745–26 during the decay of the 2013 outburst using INTEGRAL ISGRI, JEM-X and Swift XRT. The X-ray evolution is compared to the evolution in optical and radio. We fit the X-ray spectra with phenomenological and Comptonization models. We discuss possible scenarios for the physical origin of an ~50 d flare observed both in optical and X-rays ~170 d after the peak of the outburst. We conclude that it is a result of enhanced mass accretion in response to an earlier heating event. We characterized the evolution in the hard-X-ray band and showed that for the joint ISGRI–XRT fits, the e-folding energy decreased from 350 to 130 keV, while the energy where the exponential cut-off starts increased from 75 to 112 keV as the decay progressed. We investigated the claim that high-energy cut-offs disappear with the compact jet turning on during outburst decays, and showed that spectra taken with HEXTE on RXTE provide insufficient quality to characterize cut-offs during the decay for typical hard-X-ray fluxes. Long INTEGRAL monitoring observations are required to understand the relation between the compact jet formation and hard-X-ray behaviour. We found that for the entire decay (including the flare), the X-ray spectra are consistent with thermal Comptonization, but a jet synchrotron origin cannot be ruled out.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
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  • 10
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    Irradiation of an accretion disc by a jet: general properties and implications for spin measurements of black holes (2013)
    Oxford University Press
    Details
    Publikationsdatum: 2013-03-16
    Beschreibung: X-ray irradiation of the accretion disc leads to strong reflection features, which are then broadened and distorted by relativistic effects. We present a detailed, general relativistic approach to model this irradiation for different geometries of the primary X-ray source. These geometries include the standard point source on the rotational axis as well as more jet-like sources, which are radially elongated and accelerating. Incorporating this code in the relline model for relativistic line emission, the line shape for any configuration can be predicted. We study how different irradiation geometries affect the determination of the spin of the black hole. Broad emission lines are produced only for compact irradiating sources situated close to the black hole. This is the only case where the black hole spin can be unambiguously determined. In all other cases the line shape is narrower, which could either be explained by a low spin or an elongated source. We conclude that in those cases and independent of the quality of the data no unique solution for the spin exists and therefore only a lower limit of the spin value can be given.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
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