Dynamical Bar-Mode Instability in Differentially Rotating Magnetized Neutron Stars (2009)
Camarda, Karen D., Anninos, Peter, Fragile, P. Chris, Font, José A.
This paper presents a numerical study over a wide parameter space of the likelihood of the dynamical bar-mode instability in differentially rotating magnetized neutron stars. The innovative aspect of...
Effective Inner Radius of Tilted Black Hole Accretion Disks (2009)
One of the primary means of determining the spin of an astrophysical black hole is by actually measuring the inner radius of a surrounding accretion disk and using that to infer the spin. By...
Henisey, Ken B., Blaes, Omer M., Fragile, P. Chris, Ferreira, Bárbara T.
We analyze the time dependence of fluid variables in general relativistic, magnetohydrodynamic simulations of accretion flows onto a black hole with dimensionless spin parameter a/M=0.9. We consider...
Dexter, Jason, Agol, Eric, Fragile, P. Chris
The recent VLBI observation of the Galactic center black hole candidate Sgr A* at 1.3mm shows source structure on event-horizon scales. This detection enables a direct comparison of the emission...
Gamma-Ray Burst Pulse Correlations as Redshift Indicators (2009)
Hakkila, Jon, Fragile, P. Chris, Giblin, Timothy W.
Correlations among pulse properties in the prompt emission of long GRBs can potentially be used as cosmological distance indicators to estimate redshifts of GRBs to which these pulses belong. We...
Low frequency QPO spectra and Lense-Thirring precession (2009)
Ingram, Adam, Done, Chris, Fragile, P Chris
We show that the low frequency QPO seen in the power density spectra of black hole binaries (and neutron stars) can be explained by Lense-Thirring precession. This has been proposed many times in the...
Fragile, P. Chris, Meier, David L.
(Abridged) We present one of the first physically-motivated two-dimensional general relativistic magnetohydrodynamic (GRMHD) numerical simulations of a radiatively-cooled black-hole accretion disk....
Jet Formation in MHD Simulations (2008)
In this talk I review the current status of jet formation in direct numerical simulations of black-hole accretion disks and magnetospheres. I address the following critical questions: What...
Application of the Cubed-Sphere Grid to Tilted Black-Hole Accretion Disks (2008)
Fragile, P. Chris, Lindner, Christopher C., Anninos, Peter, Salmonson, Jay D.
In recent work we presented the first results of global general relativistic magnetohydrodynamic (GRMHD) simulations of tilted (or misaligned) accretion disks around rotating black holes. The...
Fragile, P. Chris, Blaes, Omer M.
This work presents a detailed analysis of the overall flow structure and unique features of the inner region of the tilted disk simulations described in Fragile et al. (2007). The primary new feature...
Correlations Between Lag, Luminosity, and Duration in Gamma-ray Burst Pulses (2008)
Hakkila, Jon, Giblin, Timothy W., Norris, Jay P., Fragile, P. Chris, Bonnell, Jerry T.
We derive a new peak lag vs. peak luminosity relation in gamma-ray burst (GRB) pulses. We demonstrate conclusively that GRB spectral lags are pulse rather than burst properties and show how the lag...
Global General Relativistic MHD Simulation of a Tilted Black-Hole Accretion Disk (2007)
Fragile, P. Chris, Blaes, Omer M., Anninos, Peter, Salmonson, Jay D.
This paper presents a continuation of our efforts to numerically study accretion disks that are misaligned (tilted) with respect to the rotation axis of a Kerr black hole. Here we present results of...
Fragile, P. Chris, Anninos, Peter, Blaes, Omer M., Salmonson, Jay D.
We posit that accreting compact objects, including stellar mass black holes and neutron stars as well as supermassive black holes, may undergo extended periods of accretion during which the angular...
Numerical Modeling of the Radio Nebula from the 2004 December 27 Giant Flare of SGR 1806-20 (2006)
Salmonson, Jay D., Fragile, P. Chris, Anninos, Peter
We use the relativistic hydrodynamics code Cosmos++ to model the evolution of the radio nebula triggered by the Dec. 27, 2004 giant flare event of soft gamma repeater 1806-20. We primarily focus on...
Anninos, Peter, Fragile, P. Chris, Salmonson, Jay D.
A new code and methodology are introduced for solving the general relativistic magnetohydrodynamic (GRMHD) equations in fixed background spacetimes using time-explicit, finite-volume discretization....
Iron-Line Emission as a Probe of Bardeen-Petterson Accretion Disks (2005)
Fragile, P. Chris, Miller, Warner A., Vandernoot, Eric
In this work we show that Bardeen-Petterson accretion disks can exhibit unique, detectable features in relativistically broadened emission line profiles. Some of the unique characteristics include...
Quasi-Periodic Oscillations in Relativistic Tori (2005)
Motivated by recent interesting work on p-mode oscillations in axisymmetric hydrodynamic black-hole tori by Rezzolla, Zanotti, and collaborators, I explore the robustness of these oscillations by...
Magnetohydrodynamic Simulations of Shock Interactions with Radiative Clouds (2004)
Fragile, P. Chris, Anninos, Peter, Gustafson, Kyle, Murray, Stephen D.
We present results from two-dimensional numerical simulations of the interactions between magnetized shocks and radiative clouds. Our primary goal is to characterize the dynamical evolution of the...
Ejection of Supernova-Enriched Gas From Dwarf Disk Galaxies (2004)
Fragile, P. Chris, Murray, Stephen D., Lin, Douglas N. C.
We examine the efficiency with which supernova-enriched gas may be ejected from dwarf disk galaxies, using a methodology previously employed to study the self-enrichment efficiency of dwarf...
Hydrodynamic Simulations of Tilted Thick-Disk Accretion onto a Kerr Black Hole (2004)
Fragile, P. Chris, Anninos, Peter
We present results from fully general relativistic three-dimensional numerical studies of thick-disk accretion onto a rapidly-rotating (Kerr) black hole with a spin axis that is tilted (not aligned)...
Radiative Shock-Induced Collapse of Intergalactic Clouds (2003)
Fragile, P. Chris, Murray, Stephen D., Anninos, Peter, Van Breugel, Wil
Accumulating observational evidence for a number of radio galaxies suggests an association between their jets and regions of active star formation. The standard picture is that shocks generated by...
Supernova Enrichment of Dwarf Spheroidal Galaxies (2003)
Fragile, P. Chris, Murray, Stephen D., Anninos, Peter, Lin, Douglas N. C.
(Abridged) Many dwarf galaxies exhibit sub-Solar metallicities, with some star-to-star variation, despite often containing multiple generations of stars. The total metal content in these systems is...
COSMOS: A Radiation-Chemo-Hydrodynamics Code for Astrophysical Problems (2003)
Anninos, Peter, Fragile, P. Chris, Murray, Stephen D.
We have developed a new massively-parallel radiation-hydrodynamics code (Cosmos) for Newtonian and relativistic astrophysical problems that also includes radiative cooling, self-gravity, and...
Hydrodynamic Stability of Cosmological Quark-Hadron Phase Transitions (2003)
Fragile, P. Chris, Anninos, Peter
Recent results from linear perturbation theory suggest that first-order cosmological quark-hadron phase transitions occurring as deflagrations may be ``borderline'' unstable, and those occurring as...
Anninos, Peter, Fragile, P. Chris
High resolution, non-oscillatory, central difference (NOCD) numerical schemes are introduced as alternatives to more traditional artificial viscosity (AV) and Godunov methods for solving the fully...
Bardeen-Petterson Effect and Quasi-Periodic Oscillations in X-Ray Binaries (2000)
Fragile, P. Chris, Mathews, Grant J., Wilson, James R.
The Bardeen-Petterson effect around a rapidly-rotating compact object causes a tilted accretion disk to warp into the equatorial plane of the rotating body. Viscous forces cause the accretion flow to...