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Dive into the research topics where Burkhard Zink is active.

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Featured researches published by Burkhard Zink.


Physical Review Letters | 2007

3D Collapse of Rotating Stellar Iron Cores in General Relativity Including Deleptonization and a Nuclear Equation of State

Christian D. Ott; Harald Dimmelmeier; Andreas Marek; Hans-Thomas Janka; Ian Hawke; Burkhard Zink

We present 2D and 3D simulations of the collapse of rotating stellar iron cores in general relativity employing a nuclear equation of state and an approximate treatment of deleptonization. We compare fully general relativistic and conformally flat evolutions and find that the latter treatment is sufficiently accurate for the core-collapse supernova problem. We focus on gravitational wave (GW) emission from rotating collapse, bounce, and early postbounce phases. Our results indicate that the GW signature of these phases is much more generic than previously estimated. We also track the growth of a nonaxisymmetric instability in one model, leading to strong narrow-band GW emission.


General Relativity and Gravitation | 2011

Gravitational waves from neutron stars: promises and challenges

Nils Andersson; Valeria Ferrari; D. I. Jones; Kostas D. Kokkotas; Badri Krishnan; J. Read; Luciano Rezzolla; Burkhard Zink

We discuss different ways that neutron stars can generate gravitational waves, describe recent improvements in modelling the relevant scenarios in the context of improving detector sensitivity, and show how observations are beginning to test our understanding of fundamental physics. The main purpose of the discussion is to establish promising science goals for third-generation ground-based detectors, like the Einstein Telescope, and identify the various challenges that need to be met if we want to use gravitational-wave data to probe neutron star physics.


Classical and Quantum Gravity | 2007

Rotating collapse of stellar iron cores in general relativity

Christian D. Ott; Harald Dimmelmeier; Andreas Marek; Hans-Thomas Janka; Burkhard Zink; Ian Hawke

We present results from the first 2 + 1 and 3 + 1 simulations of the collapse of rotating stellar iron cores in general relativity employing a finite-temperature equation of state and an approximate treatment of deleptonization during collapse. We compare full 3 + 1 and conformally-flat spacetime evolution methods and find that the conformally-flat treatment is sufficiently accurate for the core-collapse supernova problem. We focus on the gravitational wave (GW) emission from rotating collapse, core bounce and early postbounce phases. Our results indicate that the GW signature of these phases is much more generic than previously estimated. In addition, we track the growth of a nonaxisymmetric instability of dominant m = 1 character in two of our models that leads to prolonged narrow-band GW emission at ~920–930 Hz over several tens of milliseconds.


Physical Review D | 2012

Are gravitational waves from giant magnetar flares observable

Burkhard Zink; P. D. Lasky; Kostas D. Kokkotas

Are giant flares in magnetars viable sources of gravitational radiation? Few theoretical studies have been concerned with this problem, with the small number using either highly idealized models or assuming a magnetic field orders of magnitude beyond what is supported by observations. We perform nonlinear general-relativistic magnetohydrodynamics simulations of large-scale hydromagnetic instabilities in magnetar models. We utilise these models to find gravitational wave emissions over a wide range of energies, from 10^40 to 10^47 erg. This allows us to derive a systematic relationship between the surface field strength and the gravitational wave strain, which we find to be highly nonlinear. In particular, for typical magnetar fields of a few times 10^15 G, we conclude that a direct observation of f-modes excited by global magnetic field reconfigurations is unlikely with present or near-future gravitational wave observatories, though we also discuss the possibility that modes in a low-frequency band up to 100 Hz could be sufficiently excited to be relevant for observation.


Physical Review D | 2008

Multipatch methods in general relativistic astrophysics: Hydrodynamical flows on fixed backgrounds

Burkhard Zink; Manuel Tiglio

Many systems of interest in general relativistic astrophysics, including neutron stars, accreting compact objects in x-ray binaries and active galactic nuclei, core collapse, and collapsars, are assumed to be approximately spherically symmetric or axisymmetric. In Newtonian or fixed-background relativistic approximations it is common practice to use spherical polar coordinates for computational grids; however, these coordinates have singularities and are difficult to use in fully relativistic models. We present, in this series of papers, a numerical technique which is able to use effectively spherical grids by employing multiple patches. We provide detailed instructions on how to implement such a scheme, and present a number of code tests for the fixed-background case, including an accretion torus around a black hole.


Monthly Notices of the Royal Astronomical Society | 2013

The runaway instability in general relativistic accretion discs

Oleg Korobkin; Ernazar Abdikamalov; Nikolaos Stergioulas; Burkhard Zink; Stephan Rosswog; Christian D. Ott

When an accretion disc falls prey to the runaway instability, a large portion of its mass is devoured by the black hole within a few dynamical times. Despite decades of effort, it is still unclear under what conditions such an instability can occur. The technically most advanced relativistic simulations to date were unable to find a clear sign for the onset of the instability. In this work, we present three-dimensional relativistic hydrodynamics simulations of accretion discs around black holes in dynamical space–time. We focus on the configurations that are expected to be particularly prone to the development of this instability. We demonstrate, for the first time, that the fully self-consistent general relativistic evolution does indeed produce a runaway instability.


Physical Review Letters | 2011

f-Mode instability in relativistic neutron stars.

Erich Gaertig; Kostas Glampedakis; Kostas D. Kokkotas; Burkhard Zink

We present the first calculation of the basic properties of the f-mode instability in rapidly rotating relativistic neutron stars, adopting the Cowling approximation. By accounting for dissipation in neutron star matter, i.e., shear or bulk viscosity and superfluid mutual friction, we calculate the associated instability window. For our specific stellar model, a relativistic polytrope, we obtain a minimum gravitational growth time scale (for the dominant ℓ=m=4 mode) of the order of 10(3)-10(4)  s near the Kepler frequency Ω(K) while the instability is active above ∼0.92  Ω(K) and for temperatures ∼(10(9)-2×10(10))  K, characteristic of newborn neutron stars.


Physical Review D | 2010

Frequency band of the f -mode Chandrasekhar-Friedman-Schutz instability

Burkhard Zink; Oleg Korobkin; Nikolaos Stergioulas

Burkhard Zink,1 Oleg Korobkin,2 Erik Schnetter,2, 3 and Nikolaos Stergioulas4 1Theoretical Astrophysics, University of Tübingen, Auf der Morgenstelle 10, Tübingen 72076, Germany 2Center for Computation and Technology, Louisiana State University, Baton Rouge, LA 70803, USA 3Department of Physics & Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA 4Department of Physics, Section of Astrophysics, Astronomy and Mechanics Aristotle, University of Thessaloniki, Thessaloniki, 54124 Greece


Physical Review D | 2007

Nonaxisymmetric instability and fragmentation of general relativistic quasitoroidal stars

Burkhard Zink; Nikolaos Stergioulas; Ian Hawke; Christian D. Ott; Ewald Müller

In a recent publication, we have demonstrated that differentially rotating stars admit new channels of black hole formation via fragmentation instabilities. Since a higher order instability of this kind could potentially transform a differentially rotating supermassive star into a multiple black hole system embedded in a massive accretion disk, we investigate the dependence of the instability on parameters of the equilibrium model. We find that many of the models constructed exhibit non-axisymmetric instabilities with corotation points, even for low values of T/|W|, which lead to a fission of the stars into one, two or three fragments, depending on the initial perturbation. At least in the models selected here, an m=1 mode becomes unstable at lower values of T/|W|, which would seem to favor a scenario where one black hole with a massive accretion disk forms. In this case, we have gained evidence that low values of compactness of the initial model can lead to a stabilization of the resulting fragment, thus preventing black hole formation in this scenario.


Proceedings of the 15th ACM Mardi Gras conference on From lightweight mash-ups to lambda grids: Understanding the spectrum of distributed computing requirements, applications, tools, infrastructures, interoperability, and the incremental adoption of key capabilities | 2008

A case study for petascale applications in astrophysics: simulating gamma-ray bursts

Christian D. Ott; Gabrielle Allen; Edward Seidel; Jian Tao; Burkhard Zink

Petascale computing will allow astrophysicists to investigate astrophysical objects, systems, and events that cannot be studied by current observational means and that were previously excluded from computational study by sheer lack of CPU power and appropriate codes. Here we present a pragmatic case study, focussing on the simulation of gamma-ray bursts as a science driver for petascale computing. We estimate the computational requirements for such simulations and delineate in what way petascale and peta-grid computing can be utilized in this context.

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Nikolaos Stergioulas

Aristotle University of Thessaloniki

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Ian Hawke

University of Southampton

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Oleg Korobkin

Louisiana State University

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Peter Diener

Louisiana State University

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