A5087523470- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Particle physics theoretical and experimental studies
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Muon and positron interactions and applications
- Neutrino Physics Research
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Particle Detector Development and Performance
- High-Energy Particle Collisions Research
- Astronomy and Astrophysical Research
- Quantum Chromodynamics and Particle Interactions
- Particle Accelerators and Free-Electron Lasers
- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Mechanics and Biomechanics Studies
- International Science and Diplomacy
- High-pressure geophysics and materials
- Microscopic Colitis
- Laser-Plasma Interactions and Diagnostics
- Medical Imaging Techniques and Applications
- Magnetic confinement fusion research
Daresbury Laboratory
2012-2024
Imperial College London
2015-2024
Guy's and St Thomas' NHS Foundation Trust
2024
Princeton University
2014-2023
Flatiron Institute
2020-2023
Flatiron Health (United States)
2020-2023
Partners In Care
2022-2023
Saint Thomas - Rutherford Hospital
2023
Simons Foundation
2023
General Atomics (United States)
2022
The design and implementation of a new framework for adaptive mesh refinement (AMR) calculations is described. It intended primarily applications in astrophysical fluid dynamics, but its flexible modular enables use wide variety physics. works with both uniform nonuniform grids Cartesian curvilinear coordinate systems. adopts dynamic execution model based on simple called "task list" that improves parallel performance by overlapping communication computation, simplifies the inclusion diverse...
We calculate the gravitational-wave (GW) signatures of detailed three-dimensional (3D) core-collapse supernova simulations spanning a range massive stars. Most are carried out to times late enough capture more than 95% total GW emission. find that $f/g$-mode and $f$-mode protoneutron star oscillations carry away most power. The frequency inexorably rises as (PNS) core shrinks. demonstrate emission is excited mostly by accretion plumes onto PNS energize modal also high-frequency (``haze'')...
ABSTRACT We present a new general relativistic magnetohydrodynamics (GRMHD) code integrated into the Athena++ framework. Improving upon techniques used in most GRMHD codes, ours allows use of advanced, less diffusive Riemann solvers, particular HLLC and HLLD. also employ staggered-mesh constrained transport algorithm suited for curvilinear coordinate systems order to maintain divergence-free constraint magnetic field. Our is designed work with arbitrary stationary spacetimes one, two, or...
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 present 3D general relativistic magnetohydrodynamic (GRMHD) simulations of the accretion flow surrounding Sagittarius A* that are initialized using larger-scale MHD $\sim$ 30 Wolf--Rayet (WR) stellar winds in Galactic center. The properties resulting on horizon scales set not by ad hoc initial conditions but observationally constrained WR with limited free parameters. For this study we assume a non-spinning black hole. Our naturally produce $\sim 10^{-8} M_\odot$ yr$^{-1}$ rate,...
This note proposes common standards and prescriptions for the effective-field-theory interpretation of top-quark measurements at LHC.
ABSTRACT Wind-fed models offer a unique way to form predictive of the accretion flow surrounding Sagittarius A*. We present 3D wind-fed magnetohydrodynamic (MHD) and general relativistic (GRMHD) simulations spanning entire dynamic range from parsec scales event horizon. expand on previous work by including non-zero black hole spin dynamically evolved electron thermodynamics. Initial conditions for these are generated observed Wolf–Rayet stellar winds in Galactic Centre. The resulting tends...
Abstract We extend the general-relativistic magnetohydrodynamics (GRMHD) capabilities of Athena++ to incorporate radiation. The intensity field in each finite-volume cell is discretized angle, with explicit transport both space and angle properly accounting for effects gravity on null geodesics, matter radiation coupled a locally implicit fashion. Here we describe numerical procedure detail, verifying its correctness suite tests. Motivated particular by black hole accretion...
The international Muon Ionization Cooling Experiment (MICE), which is under construction at the Rutherford Appleton Laboratory (RAL), will demonstrate principle of ionization cooling as a technique for reduction phase-space volume occupied by muon beam. channels are required Neutrino Factory and Collider. MICE evaluate in detail performance single lattice cell Feasibility Study 2 channel. Beam has been constructed ISIS synchrotron RAL, Step I, it characterized using beam-instrumentation...
Since the discovery of unusual prototype SN 2002cx, eponymous class Type I (hydrogen-poor) supernovae with low ejecta speeds has grown to include approximately two dozen members identified from several heterogeneous surveys, in some cases ambiguously. Here we present results a systematic study 1077 discovered by Palomar Transient Factory, leading nine new this peculiar class. Moreover, find there are distinct subclasses based on their spectroscopic, photometric, and host galaxy properties:...
Abstract In order to address the generation of neutron star magnetic fields, with particular focus on dichotomy between magnetars and radio pulsars, we consider properties dynamos as inferred from other astrophysical systems. With sufficiently low (modified) Rossby number, convective are known produce dipole-dominated fields whose strength scales flux, argue that these expectations should apply protoneutron stars (PNSs) at centers core-collapse supernovae. We analyze a suite...
Abstract Large-scale magnetic fields play a vital role in determining the angular momentum transport and generating jets/outflows accreting systems, yet their origins remain poorly understood. We focus on radiatively inefficient accretion flows (RIAFs) around black holes (BHs), conduct 3D general-relativistic magnetohydrodynamic simulations using Athena++ code. first reconfirm that magnetorotational instability driven dynamo RIAF alone does not spontaneously form magnetically arrested disk...
Abstract We investigate numerical convergence in simulations of magnetically arrested disks around spinning black holes. Using the general-relativistic magnetohydrodynamics code Athena++ , we study same system at four resolutions (up to an effective 512 × 256 cells) and with two different spatial reconstruction algorithms. The accretion rate general large-scale structure flow agree across simulations. This includes amount magnetic flux accumulated saturated state ensuing suppression...
We present 3D general relativistic magnetohydrodynamic(GRMHD) simulations of zero angular momentum accretion around a rapidly rotating black hole, modified by the presence initially uniform magnetic fields. consider serveral angles between field direction and hole spin. In resulting flows, midplane dynamics are governed reconnection-driven turbulence in magnetically arrested (or nearly arrested) state. Electromagnetic jets with outflow efficiencies ~10-200% occupy polar regions, reaching...
ABSTRACT In general relativistic magnetohydrodynamic (GRMHD) simulations, accreted magnetic flux on the black hole horizon episodically decays, during which reconnection heats up plasma near horizon, potentially powering high-energy flares like those observed in M87* and Sgr A*. We study mm observational counterparts of such flaring episodes very high resolution GRMHD simulations. The change 230 GHz expected energy depends primarily efficiency accelerating γ ≳ 100 (Te 1011 K) electrons. For...
A wide range of stellar explosions, including supernovae (SNe), tidal disruption events (TDE), and fast blue optical transients (FBOT), can occur in dusty environments initially opaque to the transient's optical/UV light, becoming visible only once dust is destroyed by rising luminosity. We present axisymmetric time-dependent radiation transport simulations dust-shrouded with \texttt{Athena++} tabulated gray opacities, which predict light-curves dust-reprocessed infrared (IR) radiation. The...
Abstract We analyze two 3D general-relativistic magnetohydrodynamic accretion simulations in the context of how they would manifest Event Horizon Telescope (EHT) observations supermassive black holes. The differ only whether initial angular momentum plasma is aligned with rapid ( a = 0.9) spin hole. Both have low net magnetic flux. Ray tracing employed to generate resolved images synchrotron emission. When using parameters appropriate for Sgr A* and assuming viewing angle hole spin, we find...
Abstract Type Ia supernovae arise from thermonuclear explosions of white dwarfs accreting a binary companion. Following the explosion, surviving donor star leaves at roughly its orbital velocity. The discovery runaway helium subdwarf US 708, and seven hypervelocity stars Gaia data, all with spatial velocities ≳900 km s −1 , strongly support scenario in which is low-mass or dwarf. Motivated by these discoveries, we perform three-dimensional hydrodynamical simulations Athena++ code, modeling...
Abstract We use Athena++ to study the hydrodynamics of repeated star−accretion disk collisions close supermassive black holes, and we discuss their implications for origin quasi-periodic eruptions (QPEs) other repeating nuclear transients. quantify impact on stellar structure, amount stripped debris, orbital properties debris. provide simple fitting functions mass loss per collision; is much larger after collisions, due dilute atmosphere shock-heated in earlier collisions. The lifetime...
Long-term observations have shown that black hole X-ray binaries exhibit strong, aperiodic variability on time-scales of a few milliseconds to seconds. The observed light curves display various characteristic features like log-normal distribution flux and linear rms-flux relation, which indicate the underlying process is stochastic in nature. It also thought be intrinsic accretion. This has been modelled as inward propagating fluctuations mass accretion rate, although physical driving...
We compare the 230 GHz near-horizon emission from Sagittarius A* to simulations representing three classes of accretion flows. Using structure function capture variability statistics light curve, we find a noticeable discrepancy between observations and models based on torus-fed disks, whether those disks bring in small or large amount net magnetic flux. On other hand, that are fed more realistically by stellar winds match observed very well. describe differences models, arguing feeding may...
Despite the significant increase in cyber threats to space systems, structured technical community engagement cybersecurity and mission resilience with an emphasis on systematic advancement of guidance is lacking. The international group co-authors propose development a system standard intended for commercial-off-the-shelf (COTS) modular such as CubeSats.
Abstract We describe the Blacklight code, intended for postprocessing general-relativistic magnetohydrodynamic simulation data. Beyond polarized ray tracing of synchrotron radiation, it can produce a number outputs that aid in analyzing data sets, such as maps auxiliary quantities and false-color renderings. Additional features include support adaptive mesh refinement input, slow-light calculations, tracing. The code is written with ease use, readability, transparency primary objectives,...
Some binary systems composed of a white dwarf (WD) and hot subdwarf (sdB) helium star will make contact within the burning lifetime sdB star. The accreted on WD inevitably undergoes thermonuclear instability, causing detonation that is expected to transition into core lead supernova while donor orbits nearby with high velocity. Motivated by recent discovery fast-moving objects occupy unusual locations HR diagram, we explore impact supernovae donors in this specific double scenario. We use...