Magnetohydrodynamic Simulations of Gamma-Ray Burst Jets: Beyond the Progenitor Star (2009)
Tchekhovskoy, Alexander, Narayan, Ramesh, McKinney, Jonathan C.
Achromatic breaks in afterglow light curves of gamma-ray bursts (GRBs) arise naturally when the product of the jet's Lorentz factor \gamma and opening angle \Theta_j satisfies \gamma\Theta_j >> 1....
Steiner, James F., McClintock, Jeffrey E., Remillard, Ronald A., Narayan, Ramesh, Gou, Lijun
All prior work on measuring the spins of stellar-mass black holes via the X-ray continuum-fitting method has relied on the use of weakly-Comptonized spectra obtained in the thermal dominant state....
Hickox, Ryan C., Jones, Christine, Forman, William R., Murray, Stephen S., Kochanek, Christopher S., Eisenstein, Daniel, ...
We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of...
The Event Horizon of Sagittarius A* (2009)
Broderick, Avery E., Loeb, Abraham, Narayan, Ramesh
Black hole event horizons, causally separating the external universe from compact regions of spacetime, are one of the most exotic predictions of General Relativity (GR). Until recently, their...
Efficiency of Magnetic to Kinetic Energy Conversion in a Monopole Magnetosphere (2009)
Tchekhovskoy, Alexander, McKinney, Jonathan C., Narayan, Ramesh
Unconfined relativistic outflows from rotating, magnetized compact objects are often well-modeled by assuming the field geometry is approximately a split-monopole at large radii. Prior work has...
Stability of Relativistic Force-Free Jets (2009)
Narayan, Ramesh, Li, Jason, Tchekhovskoy, Alexander
We consider a two-parameter family of cylindrical force-free equilibria, modeled to match numerical simulations of relativistic force-free jets. We study the linear stability of these equilibria,...
Hickox, Ryan C., Jones, Christine, Forman, William R., Murray, Stephen S., Kochanek, Christopher S., Eisenstein, Daniel, ...
We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of...
A Determination of the Spin of the Black Hole Primary in LMC X-1 (2009)
Gou, Lijun, McClintock, Jeffrey E., Liu, Jifeng, Narayan, Ramesh, Steiner, James F., Remillard, Ronald A., ...
The first extragalactic X-ray binary, LMC X-1, was discovered in 1969. In the 1980s, its compact primary was established as the fourth dynamical black-hole candidate. Recently, we published accurate...
Gamma-ray Burst 080319B: Evidence for Relativistic Turbulence, Not Internal Shocks (2008)
We show that the excellent optical and gamma-ray data available for GRB 080319B rule out the internal shock model for the prompt emission. The data instead point to a model in which the observed...
A Turbulent Model of Gamma-Ray Burst Variability (2008)
A popular paradigm to explain the rapid temporal variability observed in gamma-ray burst (GRB) lightcurves is the internal shock model. We propose an alternative model in which the radiating fluid in...
A New Dynamical Model for the Black Hole Binary LMC X-1 (2008)
Orosz, Jerome A., Steeghs, Danny, McClintock, Jeffrey E., Torres, Manuel A. P., Bochkov, Ivan, Gou, Lijun, ...
We present a dynamical model of the high mass X-ray binary LMC X-1 based on high-resolution optical spectroscopy and extensive optical and near-infrared photometry. From our new optical data we find...
A Simple Comptonization Model (2008)
Steiner, James F., Narayan, Ramesh, McClintock, Jeffrey E., Ebisawa, Ken
We present an empirical model of Comptonization for fitting the spectra of X-ray binaries. This model, "simpl", has been developed as a package implemented in XSPEC. With only two free parameters,...
Li, Li-Xin, Narayan, Ramesh, McClintock, Jeffrey E.
Spin parameters of stellar-mass black holes in X-ray binaries are currently being estimated by fitting the X-ray continuum spectra of their accretion disk emission. For this method, it is necessary...
Shafee, Rebecca, McKinney, Jonathan C., Narayan, Ramesh, Tchekhovskoy, Alexander, Gammie, Charles F., McClintock, Jeffrey E.
We describe three-dimensional general relativistic magnetohydrodynamic simulations of a geometrically thin accretion disk around a non-spinning black hole. The disk has a thickness $h/r\sim0.05-0.1$...
Mass Fall-back and Accretion in the Central Engine of Gamma-Ray Bursts (2008)
Kumar, Pawan, Narayan, Ramesh, Johnson, Jarrett L.
We calculate the rate of in-fall of stellar matter on an accretion disk during the collapse of a rapidly rotating massive star, and estimate the luminosity of the relativistic jet that results from...
Properties of Gamma-Ray Burst Progenitor Stars (2008)
Kumar, Pawan, Narayan, Ramesh, Johnson, Jarrett L.
We determine some basic properties of stars that produce spectacular gamma-ray bursts at the end of their life. We assume that accretion of the outer portion of the stellar core by a central black...
Embedded Oscillating Starless Cores (2008)
Broderick, Avery E., Narayan, Ramesh, Keto, Eric, Lada, Charles J.
In a previous paper we demonstrated that non-radial hydrodynamic oscillations of a thermally-supported (Bonnor-Ebert) sphere embedded in a low-density, high-temperature medium persist for many...
Simulations of Ultrarelativistic Magnetodynamic Jets from Gamma-ray Burst Engines (2008)
Tchekhovskoy, Alexander, McKinney, Jonathan C., Narayan, Ramesh
Long-duration gamma-ray bursts (GRBs) require an engine capable of driving a jet of plasma to ultrarelativistic bulk Lorentz factors of up to several hundred and into narrow opening angles of a few...
Precise Measurement of the Spin Parameter of the Stellar-Mass Black Hole M33 X-7 (2008)
Liu, Jifeng, McClintock, Jeffery E., Narayan, Ramesh, Davis, Shane W., Orosz, Jerome A.
In prior work, {\it Chandra} and Gemini-North observations of the eclipsing X-ray binary M33 X-7 have yielded measurements of the mass of its black hole primary and the system's orbital inclination...
Advection-Dominated Accretion and the Black Hole Event Horizon (2008)
Narayan, Ramesh, McClintock, Jeffrey E.
As the luminosity of an accreting black hole drops to a few percent of Eddington, the spectrum switches from the familiar soft state to a hard state that is well-described by a distended and tenuous...
A simplified global solution for an advection-dominated accretion flow (2008)
Yuan, Feng, Ma, Renyi, Narayan, Ramesh
When we model black hole accretion sources such as active galactic nuclei and black hole X-ray binaries as advection-dominated accretion flows (ADAFs), it is neccesary to use the global solution to...
Dynamical Constraints on the Local Group from the CMB and 2MRS Dipoles (2007)
Loeb, Abraham, Narayan, Ramesh
We place constraints on the dynamics of the Local Group (LG) by comparing the dipole of the Cosmic Microwave Background (CMB) with the peculiar velocity induced by the 2MRS galaxy sample. The...
Advection-Dominated Accretion and Black Hole Event Horizons (2007)
Ramesh Narayan, Michael R. Garcia, Jeffrey E. Mcclintock
The defining characteristic of a black hole is that it possesses an event horizon through which matter and energy can fall in but from which nothing escapes. Soft X-ray transients (SXTs), a class of...
Spectral Signatures and Physics of Black Hole Accretion Disks (2007)
Abstract. This review summarizes the x-and-gamma-ray signatures of Galactic black hole candidates and highlights some of the accretion disk models relevant to the formation of the observable spectra...
Advection-Dominated Models of Luminous Accreting Black Holes (2007)
It has been found that a class of optically thin two-temperature advection-dominated accretion solutions explains many observations of low-luminosity accreting black holes. Here it is shown that...
Lithium Production in Hot Advection-Dominated Accretion Flows in Soft X-Ray Transients (2007)
High Li abundances have been reported in the late type secondaries of four soft X-ray transients (SXTs), V404 Cyg, A0620-00, GS2000+25, and Cen X-4. Since Li is likely to be depleted in stars of this...
Advection-Dominated Accretion Flows: Optically Thin Solutions (2007)
General properties of advection-dominated accretion flows are discussed. Special emphasis is given to the optically thin branch of solutions, which has very high ion and electron temperatures and is...
Maximum Likelihood Cluster Reconstruction (2007)
Matthias Bartelmann, Ramesh Narayan, Stella Seitz, Peter Schneider
We present a novel method to reconstruct the mass distribution of galaxy clusters from their gravitational lens effect on background galaxies. The method is based on a least-x 2 fit of the...
Neal Krawetz, Ganesh Jayadevan, Ramesh Narayan, Charlie Richardson, Paul Brutch, Kyle Walzel, ...
Abstract. A remote monitoring (RMON) agent allows system management tools access to subnets that they are not immediately connected to. The RMON Agent must be capable of processing many packets with...
Estimating the Spins of Stellar-Mass Black Holes by Fitting Their Continuum Spectra (2007)
Narayan, Ramesh, McClintock, Jeffrey E., Shafee, Rebecca
We have used the Novikov-Thorne thin disk model to fit the continuum X-ray spectra of three transient black hole X-ray binaries in the thermal state. From the fits we estimate the dimensionless spin...
A 15.65 solar mass black hole in an eclipsing binary in the nearby spiral galaxy Messier 33 (2007)
Orosz, Jerome A., McClintock, Jeffrey E., Narayan, Ramesh, Bailyn, Charles D., Hartman, Joel D., Mracri, Lucas, ...
Stellar-mass black holes are discovered in X-ray emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty...
Orosz, Jerome A., McClintock, Jeffrey E., Narayan, Ramesh, Bailyn, Charles D., Hartman, Joel D., Macri, Lucas, ...
This Supplementary Information provides details about the spectral extraction (crowding issues and the removal of nebular lines), a discussion about the distance to M33, a model for the O-star wind...
Oscillating Starless Cores: The Nonlinear Regime (2007)
Broderick, Avery E., Keto, Eric, Lada, Charles J., Narayan, Ramesh
In a previous paper, we modeled the oscillations of a thermally-supported (Bonnor-Ebert) sphere as non-radial, linear perturbations following a standard analysis developed for stellar pulsations. The...
Estimating the Spins of Stellar-Mass Black Holes (2007)
McClintock, Jeffrey E., Narayan, Ramesh, Shafee, Rebecca
We describe a program that we have embarked on to estimate the spins of stellar-mass black holes in X-ray binaries. We fit the continuum X-ray spectrum of the radiation from the accretion disk using...
Shafee, Rebecca, Narayan, Ramesh, McClintock, Jeffrey E.
We consider a simple Newtonian model of a steady accretion disk around a black hole. The model is based on height-integrated hydrodynamic equations, alpha-viscosity, and a pseudo-Newtonian potential...
High Energy Afterglow from Gamma-ray Bursts (2007)
Fan, Yi-Zhong, Piran, Tsvi, Narayan, Ramesh, Wei, Da-Ming
We calculate the very high energy (sub-GeV to TeV) inverse Compton emission of GRB afterglows. We argue that this emission provides a powerful test of the currently accepted afterglow model. We focus...
Magnetic Helicity and the Relaxation of Fossil Fields (2007)
Broderick, Avery E., Narayan, Ramesh
In the absence of an active dynamo, purely poloidal magnetic field configurations are unstable to large-scale dynamical perturbations, and decay via reconnection on an Alfvenic timescale....
Multi-dimensional Treatment of Photon Emission from Accretion Disks around Black Holes (2007)
Kohri, Kazunori, Ohsuga, Ken, Narayan, Ramesh
We consider photon emission from a supercritical accretion disk in which photons in the inner regions are trapped and advected in towards the center. Such disks are believed to be present in failed...
Where are all the gravastars? Limits upon the gravastar model from accreting black holes (2007)
Broderick, Avery E., Narayan, Ramesh
The gravastar model, which postulates a strongly correlated thin shell of anisotropic matter surrounding a region of anti-de Sitter space, has been proposed as an alternative to black holes. We...
The Latitude of Type I X-Ray Burst Ignition on Rapidly Rotating Neutron Stars (2007)
Cooper, Randall L., Narayan, Ramesh
We investigate the latitude at which type I X-ray bursts are ignited on rapidly rotating accreting neutron stars. We find that, for a wide range of accretion rates, ignition occurs preferentially at...
A 15.65-solar-mass black hole in an eclipsing binary in the nearby spiral galaxy M 33 (2007)
Orosz, Jerome A., McClintock, Jeffrey E., Narayan, Ramesh, Bailyn, Charles D., Hartman, Joel D., Macri, Lucas, ...
McClintock, Jeff, Narayan, Ramesh, Reynolds, Chris, Garcia, Michael, Orosz, Jerome, Pietsch, Wolfgang, ...
Dynamical evidence for a black hole in the eclipsing X-ray binary M33 X-7 (2007)
Orosz, Jerome A., McClintock, Jeffrey E., Bailyn, Charles D., Remillard, Ronald A., Pietsch, Wolfgang, Narayan, Ramesh
Self-Similar Force-Free Wind From an Accretion Disk (2006)
Narayan, Ramesh, McKinney, Jonathan C., Farmer, Alison J.
We consider a self-similar force-free wind flowing out of an infinitely thin disk located in the equatorial plane. On the disk plane, we assume that the magnetic stream function $P$ scales as...
Disk-Jet Coupling in Black Hole Accretion Systems II: Force-Free Electrodynamical Models (2006)
McKinney, Jonathan C., Narayan, Ramesh
In paper I, we showed that time-dependent general relativistic magnetohydrodynamic (GRMHD) numerical models of accretion disks, although being highly turbulent, have surprisingly simple...
McKinney, Jonathan C., Narayan, Ramesh
General relativistic numerical simulations of magnetized accretion flows around black holes show a disordered electromagnetic structure in the disk and corona and a highly relativistic,...
Estimating the spin of stellar-mass black holes by spectral fitting of the X-ray continuum (2006)
Shafee, Rebecca, McClintock, Jeffrey E., Narayan, Ramesh, Davis, Shane W., Li, Li-Xin, Remillard, Ronald A.
The spin of the near-extreme Kerr black hole GRS 1915+105 (2006)
McClintock, Jeffrey E., Shafee, Rebecca, Narayan, Ramesh, Remillard, Ronald A., Davis, Shane W., Li, Li-Xin
Yuan, Ye-Fei, Narayan, Ramesh, Rees, Martin J.
The existence of black holes remains open to doubt until other conceivable options are excluded. With this motivation, we consider a model of a compact star in which most of the mass consists of dark...
Lectures on gravitational lensing (1998)
Ramesh Narayan, Matthias Bartelmann
These lectures give an introduction to Gravitational Lensing. We discuss lensing by point masses, lensing by galaxies, and lensing by clusters and larger-scale structures in the Universe. The...
Kristen Menou, Ann A. Esin, Ramesh Narayan, Michael R. Garcia, Jeffrey E. Mcclintock
We consider the X-ray luminosity di†erence between neutron star and black hole soft X-ray transients (NS and BH SXTs) in quiescence. The current observational data suggest that BH SXTs are...
SMT: A system monitoring tool for DCE (1996)
Anish Karmarkar, Paul Brutch, Sunil Santha, Ramesh Narayan, Charlie Richardson, Nealkrawetz Anilgurijala, ...
Abstract. Understanding interactions among various components in a distributed system is very important for system administrators and application developers. The System Monitoring Tool 1 (SMT) was...
Rohan Mahadevan, Ramesh Narayan, Julian Krolik
We calculate the flux and spectrum of fl-rays emitted by a two-temperature advection-dominated accretion flow (ADAF) around a black hole. The fl- rays are from the decay of neutral pions produced...
Lectures on Gravitational Lensing (1996)
Ramesh Narayan, Matthias Bartelmann
Contents 1 Introduction 1 2 Lensing by Point Masses in the Universe 4 2.1 Basics of Gravitational Lensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1.1 Effective Refractive Index...
Ramesh Narayan, Michael R. Garcia, E. Mcclintock
The defining characteristic of a black hole is that it possesses an event horizon through which matter and energy can fall in but from which nothing escapes. Soft X-ray transients (SXTs), a class of...
Unified Description of Accretion Flows Around Black Holes (1995)
Chen, Xingming, Abramowicz, Marek A., Lasota, Jean-Pierre, Narayan, Ramesh, Yi, Insu
We provide a unified description of thermal equilibria of black hole accretion disks, including the newly-discovered advection-dominated solutions. We classify the solutions on the basis of optical...
Theory of divalent ions in crystals (1983)
The divalent ions in alkaline earth chalcogenides are viewed as compressible objects and are treated within a purely ionic model. As in earlier studies on the alkali and ammonium halides, the ions...
Theory of divalent ions in crystals (1983)
The divalent ions in alkaline earth chalcogenides are viewed as compressible objects and are treated within a purely ionic model. As in earlier studies on the alkali and ammonium halides, the ions...
Maximum entropy image reconstruction-A practical noninformation-theoretic approach (1982)
Rajaram Nityan, Ramesh Narayan
Abstract. The maximum entropy method (MEM) of image reconstruct-tion is discussed in the context of incomplete Fourier information (as in aperture synthesis). Several current viewpoints on the...