A5010073173- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Black Holes and Theoretical Physics
- High-pressure geophysics and materials
- Particle Accelerators and Free-Electron Lasers
- Radio Astronomy Observations and Technology
- Geophysics and Sensor Technology
- Seismic Waves and Analysis
- Superconducting Materials and Applications
- Magnetic confinement fusion research
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Atomic and Subatomic Physics Research
- Distributed and Parallel Computing Systems
- Statistical and numerical algorithms
- Relativity and Gravitational Theory
- Computational Physics and Python Applications
- Planetary Science and Exploration
- Particle accelerators and beam dynamics
- Scientific Computing and Data Management
- Solar and Space Plasma Dynamics
University of Idaho
2021-2025
West Virginia University
2015-2024
Goddard Space Flight Center
2014-2021
University of Maryland, Baltimore County
2021
University of Illinois Urbana-Champaign
2006-2015
Joint Space Science Institute
2014
University of Maryland, College Park
2014
University of Michigan
2001-2003
Binary neutron stars (NSNS) are expected to be among the leading sources of gravitational waves observable by ground-based laser interferometers and may progenitors short-hard gamma-ray bursts. We present a series general relativistic NSNS coalescence simulations both for unmagnetized magnetized stars. adopt quasiequilibrium initial data circular, irrotational binaries constructed in conformal thin-sandwich (CTS) framework. BSSN formulation evolving metric high-resolution shock-capturing...
Black hole-neutron star (BHNS) binaries are expected to be among the leading sources of gravitational waves observable by ground-based detectors, and may progenitors short-hard gamma-ray bursts (SGRBs) as well. We discuss our new fully general relativistic calculations merging BHNS binaries, which use high-accuracy, low-eccentricity, conformal thin-sandwich configurations initial data. Our evolutions performed using moving puncture method include a relativistic, high-resolution...
Black-hole--neutron-star (BHNS) binary mergers are candidate engines for generating both short-hard gamma-ray bursts and detectable gravitational waves. Using our most recent conformal thin-sandwich BHNS initial data fully general relativistic hydrodynamics code, which is now adaptive mesh refinement capable, we able to efficiently accurately simulate these binaries from large separations through inspiral, merger, ringdown. We evolve the metric using Baumgarte-Shapiro-Shibata-Nakamura...
In the extreme violence of merger and mass accretion, compact objects like black holes neutron stars are thought to launch some most luminous outbursts electromagnetic gravitational wave energy in Universe. Modeling these systems realistically is a central problem theoretical astrophysics, but has proven extremely challenging, requiring development numerical relativity codes that solve Einstein's equations for spacetime, coupled general relativistic (ideal) magnetohydrodynamics (GRMHD)...
The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational-wave data analysis communities. purpose NINJA to study sensitivity existing search algorithms using numerically generated waveforms foster closer collaboration We describe results first which focused on gravitational from binary black hole coalescence. Ten groups contributed were used generate set signals. These signals injected into simulated set, designed...
We present results from the first fully general relativistic, magnetohydrodynamic (GRMHD) simulations of an equal-mass black hole binary (BHBH) in a magnetized, circumbinary accretion disk. simulate both pre and post-decoupling phases BHBH-disk system "cooling" "no-cooling" gas flows. Prior to decoupling, competition between tidal torques effective viscous due MHD turbulence depletes disk interior orbit. However, it also induces two-stream flow mildly relativistic polar outflows BHs....
We report on simulations in general relativity of magnetized disks accreting onto black hole binaries. vary the binary mass ratio from 1:1 to 1:10 and evolve systems when they orbit near binary-disk decoupling radius. compare (surface) density profiles, accretion rates (relative a single, nonspinning hole), variability, effective $\ensuremath{\alpha}$-stress levels luminosities as functions ratio. treat two limiting regimes: rapid radiative cooling no cooling. The magnetic field lines...
Results are presented from a semi-coherent search for continuous gravitational waves the brightest low-mass X-ray binary, Scorpius X-1, using data collected during first Advanced LIGO observing run (O1). The combines frequency domain matched filter (Bessel-weighted $\mathcal{F}$-statistic) with hidden Markov model to track wandering of neutron star spin frequency. No evidence is found in range 60-650 Hz. Frequentist 95% confidence strain upper limits, $h_0^{95\%} = 4.0\times10^{-25}$,...
Abstract Recent developments in compact object astrophysics, especially the discovery of merging neutron stars by LIGO, imaging black hole M87 Event Horizon Telescope, and high- precision astrometry Galactic Center at close to event horizon scale GRAVITY experiment motivate development numerical source models that solve equations general relativistic magnetohydrodynamics (GRMHD). Here we compare GRMHD solutions for evolution a magnetized accretion flow where turbulence is promoted...
We have written and tested a new general relativistic magnetohydrodynamics (GRMHD) code, capable of evolving MHD fluids in dynamical spacetimes with adaptive-mesh refinement (AMR). Our code solves the Einstein-Maxwell-MHD system coupled equations full 3+1 dimensions, metric via Baumgarte-Shapiro Shibata-Nakamura (BSSN) formalism magnetic induction conservative, high-resolution shock-capturing scheme. The are recast as an evolution equation for vector potential, which exists on grid that is...
As a neutron star (NS) is tidally disrupted by black hole (BH) companion at the end of BH-NS binary inspiral, its magnetic fields will be stretched and amplified. If sufficiently strong, these may impact gravitational waveforms, merger evolution mass remnant disk. Formation highly-collimated field lines in disk+spinning BH launch relativistic jets, providing engine for short-hard GRB. We analyze this scenario through fully general relativistic, magnetohydrodynamic (GRMHD) BHNS simulations...
The Numerical–Relativity–Analytical–Relativity (NRAR) collaboration is a joint effort between members of the numerical relativity, analytical relativity and gravitational-wave data analysis communities. goal NRAR to produce numerical-relativity simulations compact binaries use them develop accurate templates for LIGO/Virgo Collaboration in detecting signals extracting astrophysical information from them. We describe results first stage project, which focused on producing an initial set...
We recently developed a new general relativistic magnetohydrodynamic code with adaptive mesh refinement that evolves the electromagnetic (EM) vector potential (A) instead of magnetic fields directly. Evolving A enables one to use any interpolation scheme on level boundaries and still guarantee field remains divergenceless. As in classical EM, gauge choice must be made when evolving A, we chose straightforward "algebraic" condition simplify evolution equation. However, magnetized black...
We perform the first general relativistic force-free simulations of neutron star (NS) magnetospheres in orbit about spinning and non-spinning black holes. find promising precursor electromagnetic emission: typical Poynting luminosities at, e.g., an orbital separation 6.6 times NS radius are L ~ 6 x 10^{42} erg/s for a 1.4 solar-mass with 10^{13}G polar magnetic field. The flux peaks within broad beam ~40 degrees azimuthal direction ~60 from plane, establishing possible lighthouse effect. Our...
The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational wave data analysis communities.The purpose NINJA to study sensitivity existing gravitational-wave search parameter-estimation algorithms using numerically generated waveforms, foster closer collaboration first used only small number injections short numerical-relativity which limited its ability draw quantitative conclusions.The goal NINJA-2 overcome these...
We report results from simulations in general relativity of magnetized disks accreting onto merging black hole binaries, starting relaxed disk initial data. The feature an effective, rapid radiative cooling scheme as a limiting case future treatments with transfer. Here we evolve the systems after binary-disk decoupling through inspiral and merger, analyze dependence on binary mass ratio $q\equiv m_{\rm bh}/M_{\rm BH}=1,1/2,$ $1/4$. find that luminosity associated local is larger than matter...
We follow the inspiral and merger of equal-mass black holes (BHs) by moving puncture technique demonstrate that both exterior solution asymptotic gravitational waveforms are unchanged when initial interior is replaced constraint-violating junk data. apply this result to evolve conformal thin-sandwich (CTS) binary BH data filling their excised interiors with arbitrary, but smooth, evolving standard gauge choices. The generated for filled-CTS remarkably similar, there only minor differences...
The inspiral and merger of a binary neutron star (NSNS) can lead to the formation hypermassive (HMNS). As HMNS loses thermal pressure due neutrino cooling and/or centrifugal support gravitational wave emission, magnetic breaking differential rotation, it will collapse black hole. To assess importance shock-induced cooling, we adopt an idealized equation state perform NSNS simulations in full general relativity through late inspiral, merger, formation, accounting for cooling. We show that...
Black hole--neutron star (BHNS) binary mergers can form disks in which magnetorotational instability (MRI)-induced turbulence may drive accretion onto the remnant BH, supporting relativistic jets and providing engine for a short-hard gamma-ray burst (SGRB). Our earlier study of magnetized BHNSs showed that NS tidal disruption winds magnetic field into toroidal configuration, with poloidal fields so weak capturing MRI full-disk simulations would require $\sim 10^8$ CPU-hours. In we imposed...
We present fully general relativistic (GR) simulations of binary white dwarf-neutron star (WDNS) inspiral and merger. The initial is in a circular orbit at the Roche critical separation. goal to determine ultimate fate such systems. focus on binaries whose total mass exceeds maximum (Mmax) cold, degenerate EOS can support against gravitational collapse. time length scales span many orders magnitude, making hydrodynamic (GRHD) computationally prohibitive. For this reason, we model WD as...
We report on a new open-source, user-friendly numerical relativity code package called $\mathrm{SENR}/\mathrm{NRPy}+$. Our extends previous implementations of the BSSN reference-metric formulation to much broader class curvilinear coordinate systems, making it ideally suited modeling physical configurations with approximate or exact symmetries. In context black hole dynamics, is orders magnitude more efficient than other widely used open-source codes. $\mathrm{NRPy}+$ provides Python-based...
Binary black hole (BBH) mergers provide a prime source for current and future interferometric GW observatories. Massive BBH may often take place in plasma-rich environments, leading to the exciting possibility of concurrent electromagnetic (EM) signal observable by traditional astronomical facilities. However, many critical questions about generation such counterparts remain unanswered. We explore mechanisms that drive EM with magnetohydrodynamic simulations treating range scenarios...
We show that a magnetically levitated microsphere in high vacuum can be used as an accelerometer by comparing its response to of commercially available geophone. This system shows great promise for ultrahigh acceleration sensitivities without the need large masses or cryogenics. With feedback cooling, transient decay time is reduced and center-of-mass motion cooled 9 K less. Remarkably, levitated-particle has sensitivity down...
We have added support for realistic, microphysical, finite-temperature equations of state (EOS) and neutrino physics via a leakage scheme to IllinoisGRMHD, an open-source GRMHD code dynamical spacetimes in the Einstein Toolkit. These new features are provided by two new, NRPy+-based codes: NRPyEOS, which performs highly efficient EOS table lookups interpolations, NRPyLeakage, implements AMR-capable performed series strenuous validation tests that demonstrate robustness these codes,...