A5034731703- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Geophysics and Gravity Measurements
- High-pressure geophysics and materials
- Black Holes and Theoretical Physics
- High-Energy Particle Collisions Research
- Radio Astronomy Observations and Technology
- Geophysics and Sensor Technology
- Relativity and Gravitational Theory
- Computational Fluid Dynamics and Aerodynamics
- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Fluid Dynamics and Turbulent Flows
- Galaxies: Formation, Evolution, Phenomena
- Magnetic confinement fusion research
- Atomic and Subatomic Physics Research
- Numerical methods for differential equations
- Mechanics and Biomechanics Studies
- Laser-Plasma Interactions and Diagnostics
- Particle Accelerators and Free-Electron Lasers
- Experimental and Theoretical Physics Studies
- Astro and Planetary Science
Goethe University Frankfurt
2016-2025
Goethe Institute
2025
Frankfurt Institute for Advanced Studies
2015-2025
Trinity College Dublin
2019-2025
Max Planck Institute for Radio Astronomy
2022
Shanghai Jiao Tong University
2022
University College London
2022
Max Planck Institute for Gravitational Physics
2007-2019
Kent State University
2019
Radboud University Nijmegen
2016
We explore in a parameterized manner very large range of physically plausible equations state (EOSs) for compact stars matter that is either purely hadronic or exhibits phase transition. In particular, we produce two classes EOSs with and without transitions, each containing one million EOSs. then impose constraints on the maximum mass (M<2.16 M_{⊙}) dimensionless tidal deformability (Λ[over ˜]<800) deduced from GW170817, together recent suggestions lower limits Λ[over ˜]. Exploiting more...
Abstract Combining the GW observations of merging systems binary neutron stars and quasi-universal relations, we set constraints on maximum mass that can be attained by nonrotating stellar models stars. More specifically, exploiting recent observation event GW170817 drawing from basic arguments kilonova modeling GRB 170817A together with relation between supported through uniform rotation , limits for to where lower limit in this range comes pulsar observations. Our estimate, which follows a...
Gravitational waveforms from the inspiral and ring-down stages of binary black-hole coalescences can be modeled accurately by approximation/perturbation techniques in general relativity. Recent progress numerical relativity has enabled us to model also nonperturbative merger phase coalescence problem. This enables coherently search for all three nonspinning black holes using a single template bank. Taking our motivation these results, we propose family which inspiral, merger, that follow...
Binary neutron-star systems represent primary sources for the gravitational-wave detectors that are presently operating or close to being at target sensitivities. We present a systematic investigation in full general relativity of dynamics and emission from binary neutron stars which inspiral merge, producing black hole surrounded by torus. Our results state art several points view: (i) use high-resolution shock-capturing methods solution hydrodynamics equations high-order...
Merging binaries of neutron stars are not only strong sources gravitational waves, but also have the potential revealing states matter at densities and temperatures accessible in laboratories. A crucial long-standing question this context is whether quarks deconfined as a result dramatic increase density temperature following merger. We present first fully general-relativistic simulations merging including finite that can be switched off consistently equation state. Within our approach, we...
Short gamma-ray bursts (SGRBs) are among the most luminous explosions in universe, releasing less than one second energy emitted by our Galaxy over year. Despite decades of observations, nature their "central engine" remains unknown. Considering a binary magnetized neutron stars and solving Einstein equations, we show that merger results rapidly spinning black hole surrounded hot highly torus. Lasting 35 ms much longer previous simulations, study reveals magnetohydrodynamical instabilities...
We present fully general-relativistic simulations of binary neutron star mergers with a temperature and composition dependent nuclear equation state. study the dynamical mass ejection from both quasi-circular dynamical-capture eccentric mergers. systematically vary level our treatment microphysics to isolate effects neutrino cooling heating we compute nucleosynthetic yields ejecta. find that binaries can eject significantly more material than generate bright infrared radio emission. In all...
Determining the equation of state matter at nuclear density and hence structure neutron stars has been a riddle for decades. We show how imminent detection gravitational waves from merging star binaries can be used to solve this riddle. Using large number accurate numerical-relativity simulations with equations state, we find that postmerger emission is characterized by two distinct robust spectral features. While high-frequency peak already associated oscillations hypermassive produced...
Using an extended set of equations state and a multiple-group multiple-code collaborative effort to generate waveforms, we improve numerical-relativity-based data-analysis estimates the measurability matter effects in neutron-star binaries. We vary two parameters parameterized piecewise-polytropic equation (EOS) analyze EOS properties, via parameter {\Lambda} that characterizes quadrupole deformability isolated neutron star. find that, within accuracy simulations, departure waveform from...
Collaborative international efforts under the name of Event Horizon Telescope project, using sub- mm very long baseline interferometry, are soon expected to provide first images shadow cast by candidate supermassive black hole in our Galactic center, Sagittarius A*. Observations this would direct evidence existence astrophysical holes. Although it is that holes described axisymmetric Kerr solution, there also exist many other solutions, both general relativity and theories gravity, which...
A number of recent works have highlighted that it is possible to express the properties general-relativistic stellar equilibrium configurations in terms functions do not depend on specific equation state employed describe matter at nuclear densities. These are normally referred as "universal relations" and been found apply, within limits, both static or stationary isolated stars, well fully dynamical merging binary systems. Further extending idea universal relations can be valid also away...
We present a new formulation of the Einstein equations based on conformal and traceless decomposition covariant form Z4 system. This combines advantages decomposition, such as one used in BSSNOK (i.e. well-tested hyperbolic gauges, no need for excision, robustness to imperfect boundary conditions) with constraint-damped formulation, generalized harmonic exponential decay constraint violations when these are produced). validate set through standard tests by evolving binary black hole systems....
Several fast radio bursts have been discovered recently, showing a bright, highly dispersed millisecond pulse. The pulses do not repeat and are associated with known pulsar or gamma-ray burst. high dispersion suggests sources at cosmological distances, hence implying an extremely luminosity, far larger than the power of single from pulsar. We suggest that burst represents final signal supramassive rotating neutron star collapses to black hole due magnetic braking. is initially above critical...
Extending previous work by a number of authors, we have recently presented new approach in which the detection gravitational waves from merging neutron star binaries can be used to determine equation state matter at nuclear density and hence structure stars. In particular, after performing large numerical-relativity simulations with equations state, found that post-merger emission is characterized two distinct robust spectral features. While high-frequency peak was already shown associated...
Following previous work of ours in spherical symmetry, we here propose a new parametric framework to describe the spacetime axisymmetric black holes generic metric theories gravity. In this case, components are functions both radial and polar angular coordinates, forcing double expansion obtain expression. particular, use continued-fraction terms compactified coordinate express dependence, while exploit Taylor cosine angle for dependence. These choices lead superior convergence direction an...
Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by Event Horizon Telescope (EHT). We use here M87* shadow size infer constraints on physical charges a large variety nonrotating or rotating black holes. For example, we show that quality is already sufficient rule out highly charged dilaton hole. Similarly, when considering holes with two and independent charges, are able exclude considerable regions space parameters...
We revisit the problem of predicting spin magnitude and direction black hole (BH) resulting from merger two BHs with arbitrary masses spins inspiraling in quasi-circular orbits. do this by analyzing a catalog 619 recent numerical-relativity simulations collected literature spanning large variety initial conditions. By combining information post-Newtonian approximation, extreme mass-ratio limit, perturbative calculations, we improve our previously proposed phenomenological formulae for final...
A large international effort is under way to assess the presence of a shadow in radio emission from compact source at centre our Galaxy, Sagittarius A$^*$ (Sgr A$^*$). If detected, this would provide first direct evidence existence black holes and that Sgr supermassive hole. In addition, shape could be used learn about extreme gravity near event horizon determine which theory better describes observations. The mathematical description has so far number simplifying assumptions are unlikely...
A number of works have shown that important information on the equation state matter at nuclear density can be extracted from gravitational waves emitted by merging neutron-star binaries. We present a comprehensive analysis gravitational-wave signal during inspiral, merger and post-merger 56 This sample binaries, arguably largest studied to date with realistic equations state, spans across six different nuclear-physics ten masses, allowing us sharpen results recently obtained spectral...
Inferring the properties of dense matter is one most exciting prospects from measurement gravitational waves neutron star mergers. However, it requires reliable numerical simulations that incorporate viscous dissipation and energy transport as these can play a significant role in survival time post-merger object. We calculate scales for typical forms find thermal shear viscosity will not be important unless neutrino trapping occurs, which temperatures above 10 MeV gradients over length 0.1...
We propose a new parametric framework to describe in generic metric theories of gravity the spacetime spherically symmetric and slowly rotating black holes. In contrast similar approaches proposed so far, we do not use Taylor expansion powers M/r, where M r are mass hole radial coordinate, respectively. Rather, continued-fraction terms compactified coordinate. This choice leads superior convergence properties allows us approximate number known with much smaller set coefficients. The measure...