Polarization Changes of Pulsars due to Wave Propagation Through Magnetospheres (2009)
Wang, Chen, Lai, Dong, Han, JinLin
We study the propagation effects of radio waves in a pulsar magnetosphere, composed of relativistic electron-positron pair plasmas streaming along the magnetic field lines and corotating with the...
Polarized X-rays from Magnetized Neutron Stars (2009)
Lai, Dong, Ho, Wynn C. G., Van Adelsberg, Matthew, Wang, Chen, Heyl, Jeremy S.
We review the polarization properties of X-ray emission from highly magnetized neutron stars, focusing on emission from the stellar surfaces. We discuss how x-ray polarization can be used to...
We study the effect of corotation resonance on the inertial-acoustic oscillations (p-modes) of black-hole accretion discs. Previous works have shown that for barotropic flows (where the pressure...
X-ray photons emitted from the surface or atmosphere of a magnetized neutron star is highly polarized. However, the observed polarization may be modified due to photon propagation through the star's...
Extreme Astrophysics with Neutron Stars (2009)
Lai, Dong, Van Kerkwijk, Marten, Arons, Jon, Beloborodov, Andrei, Brown, Edward, Cordes, James, ...
We highlight recent theoretical and observational progress in several areas of neutron star astrophysics, and discuss the prospect for advances in the next decade.
Interface Modes and Their Instabilities in Accretion Disc Boundary Layers (2008)
We study global non-axisymmetric oscillation modes trapped near the inner boundary of an accretion disc. Observations indicate that some of the quasi-periodic oscillations (QPOs) observed in the...
Corotational Damping of Diskoseismic C-modes in Black Hole Accretion Discs (2008)
Diskoseismic c-modes in accretion discs have been invoked to explain low-frequency variabilities observed in black-hole X-ray binaries. These modes are trapped in the inner-most region of the disc...
We study the global stability of non-axisymmetric p-modes (also called inertial-acoustic modes) trapped in the inner-most regions of accretion discs around black holes. We show that the lowest-order...
Effects of Magnetic Fields on the Diskoseismic Modes of Accreting Black Holes (2008)
The origin of the rapid quasi-periodic variabilities observed in a number of accreting black hole X-ray binaries is not understood. It has been suggested that these variabilities are associated with...
Radiation from condensed surface of magnetic neutron stars (2008)
Matthew Van Adelsberg, Dong Lai, Er Y. Potekhin
Abstract Recent observations show that thermal X-ray spectra of many isolated neutron stars are featureless and in some cases well fit by a blackbody. Such perfect blackbody spectra are puzzling as...
MODELING SPECTRAL FEATURES FROM ISOLATED NEUTRON STARS (2008)
Dong Lai, Er Y. Potekhin, Gilles Chabrier
Abstract We study several effects that influence the strength of the proton cyclotron and atomic features in the thermal spectra of magnetic neutron stars. Magnetic field variations over the neutron...
Dong Lai, Lars Bildsten, Victoria M. Kaspi
The spin-induced quadrupole moment of a rapidly rotating star changes the orbital dynamics in a binary system, giving rise to advance (or regression) of periastron and precession of the orbital...
Atmospheres Of Magnetized Neutron Stars: (2007)
Vacuum Polarization And, Dong Lai, Er Y. Potekhin, Gilles Chabrier
We construct hydrogen atmosphere models for magnetized neutron stars in radiative equilibrium with surface elds B = 10 510 G and eective temperatures T e a few10 K by solving the full radiative...
In differentially rotating discs with no self-gravity, density waves cannot propagate around the corotation, where the wave pattern rotation speed equals the fluid rotation rate. Waves incident upon...
Wave Excitation in Disks Around Rotating Magnetic Stars (2007)
The accretion disk around a rotating magnetic star (neutron star, white dwarf or T Tauri star) is subjected to periodic vertical magnetic forces from the star, with the forcing frequency equal to the...
For sufficiently strong magnetic fields and/or low temperatures, the neutron star surface may be in a condensed state with little gas or plasma above it. Such surface condensation can significantly...
Hall drift of axisymmetric magnetic fields in solid neutron-star matter (2007)
Reisenegger, Andreas, Benguria, Rafael, Prieto, Joaquin P., Araya, Pablo A., Lai, Dong
Hall drift, i. e., transport of magnetic flux by the moving electrons giving rise to the electrical current, may be the dominant effect causing the evolution of the magnetic field in the solid crust...
Radiative transitions of the helium atom in highly magnetized neutron star atmospheres (2007)
Medin, Zach, Lai, Dong, Potekhin, Alexander Y.
Recent observations of thermally emitting isolated neutron stars revealed spectral features that could be interpreted as radiative transitions of He in a magnetized neutron star atmosphere. We...
Statistical equilibrium and ion cyclotron absorption/emission in strongly magnetized plasmas (2007)
We calculate the transition rates between proton Landau levels due to non-radiative and radiative Coulomb collisions in an electron-proton plasma with strong magnetic field B. Both electron-proton...
Cohesive property of magnetized neutron star surfaces: Computations and implications (2007)
The cohesive energy of condensed matter in strong magnetic fields is a fundamental quantity characterizing magnetized neutron star surfaces. The cohesive energy refers to the energy required to pull...
Statistical equilibrium and ion cyclotron absorption/emission in strongly magnetized plasmas (2007)
Cyclotron lines are a powerful diagnostic tool for magnetized neutron stars. The detection of electron cyclotron features at 10–80 keV in the spectra of a number of binary X-ray pulsars (e.g....
Wave Modes in the Magnetospheres of Pulsars and Magnetars (2006)
We study the wave propagation modes in the relativistic streaming pair plasma of the magnetospheres of pulsars and magnetars, focusing on the effect of vacuum polarization. We show that the combined...
Probing Axions with Radiation from Magnetic Stars (2006)
Recent experiments suggest that polarized photons may couple significantly to pseudoscalar particles such as axions. We study the possible observational signatures of axion-photon coupling for...
Spin-Kick Correlation in Neutron Stars: Alignment Conditions and Implications (2006)
Wang, Chen, Lai, Dong, Han, JinLin
Recent observations of pulsar wind nebulae and radio polarization profiles revealed a tendency of the alignment between the spin and velocity directions in neutron stars. We study the condition for...
We present new, ab initio calculations of the electronic structure of one-dimensional infinite chains and three-dimensional condensed matter in strong magnetic fields ranging from B=10^12 G to...
We present new ab initio calculations of the electronic structure of various atoms and molecules in strong magnetic fields ranging from B=10^12 G to 2x10^15 G, appropriate for radio pulsars and...
Van Adelsberg, Matthew, Lai, Dong
Theoretical modeling of surface emission from magnetized neutron stars (NSs) requires proper treatment of QED effects, in particular the effect of photon mode conversion due to the ``vacuum...
Physics of Strongly Magnetized Neutron Stars (2006)
There has recently been growing evidence for the existence of neutron stars possessing magnetic fields with strengths that exceed the quantum critical field strength of $4.4 \times 10^{13}$ G, at...
Resonant Tidal Excitations of Inertial Modes in Coalescing Neutron Star Binaries (2006)
We study the effect of resonant tidal excitation of inertial modes in neutron stars during binary inspiral. For spin frequencies less than 100 Hz, the phase shift in the gravitational waveform...
Effects of Gravitational Lensing and Companion Motion on the Binary Pulsar Timing (2005)
The measurement of the Shapiro time delay in binary pulsar systems with highly inclined orbit can be affected both by the motion of the pulsar's companion because of the finite time it takes a photon...
Wave Excitation in Three-Dimensional Disks by External Potential (2005)
We study the excitation of density and bending waves and the associated angular momentum transfer in gaseous disks with finite thickness by a rotating external potential. The disk is assumed to be...
Wang, Chen, Lai, Dong, Han, JinLin
We study observational constraints on neutron star (NS) kicks for isolated pulsars and for neutron stars in binary systems. We are particularly interested in the evidence of kick-spin...
Effects of Pulsar Rotation on Timing Measurements of the Double Pulsar System J0737-3039 (2005)
We study the effect of pulsar rotation on timing of binary pulsars, with particular emphasis on the double pulsar system J0737-3039. Special relativistic aberration due to the orbital motion of...
Magnetic fields in neutron stars: A theoretical perspective (2005)
Reisenegger, Andreas, Prieto, Joaquin, Benguria, Rafael, Lai, Dong, Araya, Pablo
We present our view of the main physical ingredients determining the evolution of neutron star magnetic fields. This includes the basic properties of neutron star matter, possible scenarios for the...
Effects of Gravitational Lensing in the Double Pulsar System J0737-3039 (2004)
We investigate the effects of gravitational lensing in the binary pulsar system J0737-3039. Current measurement of the orbital inclination allows the millisecond pulsar (A) to pass very close (at...
Lai, Dong, Bildsten, Lars, Kaspi, Victoria M.
The spin-induced quadrupole moment of a rapidly rotating star changes the orbital dynamics in a binary system, giving rise to advance (or regression) of periastron and precession of the orbital...
Radiation from condensed surface of magnetic neutron stars (2004)
Van Adelsberg, Matthew, Lai, Dong, Potekhin, Alexander Y., Arras, Phil
Recent observations show that the thermal X-ray spectra of many isolated neutron stars are featureless and in some cases (e.g., RX J1856.5-3754) well fit by a blackbody. Such a perfect blackbody...
Potekhin, A. Y., Lai, Dong, Chabrier, G., Ho, W. C. G.
Polarizability tensor of a strongly magnetized plasma and the polarization vectors and opacities of normal electromagnetic waves are studied for the conditions typical of neutron star atmospheres,...
We study several effects that influence the strength of the proton cyclotron and atomic features in the thermal spectra of magnetic neutron stars. We show that it is possible for vacuum polarization...
MAGNETIC FIELDS AND NEUTRON STAR ATMOSPHERE MODELS (2004)
Er Y. Potekhin, Dong Lai, Gilles Chabrier
The polarizability tensor of a strongly magnetized plasma and the polarization vectors and opacities of normal electromagnetic waves are studied for conditions typical of neutron star atmospheres,...
Matthew Van Adelsberg, Dong Lai, Er Y. Potekhin, Phil Arras
Recent observations show that the thermal X-ray spectra of many isolated neutron stars are featureless and in some cases (e.g., RX J1856.5 3754) well fit by a blackbody. Such a perfect blackbody...
Neutron Star Kicks and Supernova Asymmetry (2003)
Observations over the last decade have shown that neutron stars receive a large kick velocity (of order a hundred to a thousand km/s) at birth. The physical origin of the kicks and the related...
Ho, Wynn C. G., Lai, Dong, Potekhin, Alexander Y., Chabrier, Gilles
We construct partially ionized hydrogen atmosphere models for magnetized neutron stars in radiative equilibrium with surface fields B=10^12-5 \times 10^14 G and effective temperatures T_eff \sim a...
Warping and Precession of Accretion Disks Around Magnetic Stars: Nonlinear Evolution (2003)
Pfeiffer, Harald P., Lai, Dong
The inner region of the accretion disk around a magnetized star (T Tauri star, white dwarf or neutron star) is subjected to magnetic torques that induce warping and precession of the disk. These...
Current theoretical models for the outflows/jets from AGN, X-ray binaries and young stellar objects involve large-scale magnetic fields threading an underlying accretion disk. We suggest that such a...
In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein like resonance across which a X-ray photon may (depending on its energy)...
Matter and Radiation in Superstrong Magnetic Fields and Thermal Emission from Neutron Stars (2003)
Thermal surface emissions have now been detected from more than a dozen isolated neutron stars, including radio pulsars, radio-quiet neutron stars and magnetars. These detections can potentially...
Core-Collapse Supernovae and Neutron Star Kicks (2002)
Recent observations have revealed many new puzzles related to core-collapse supernovae, including the formation of magnetars and black holes and their possible GRB connections. We review our current...
Atmospheres of Magnetized Neutron Stars: Vacuum Polarization and Partially Ionized Models (2002)
Ho, Wynn C. G., Lai, Dong, Potekhin, Alexander Y., Chabrier, Gilles
We construct hydrogen atmosphere models for magnetized neutron stars in radiative equilibrium with surface fields B=10^12-5x10^14 G and effective temperatures T_eff a few x 10^5-10^6 K by solving the...
We present a theoretical study of radiative transfer in strongly magnetized electron-ion plasmas, focusing on the effect of vacuum polarization due to quantum electrodynamics. This study is directly...
The inner region of the accretion disk around a magnetized star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the...
We have recently shown that in a highly magnetized neutron star atmospheric plasma, vacuum polarization can induce resonant conversion of photon polarization modes via a mechanism analogous to MSW...
We study the effect of vacuum polarization on the atmosphere structure and radiation spectra of neutron stars with surface magnetic fields B=10^14-10^15 G, as appropriate for magnetars. Vacuum...
The inner region of the accretion disk around a magnetized neutron star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between...
It is known that vacuum polarization can modify the photon propagation modes in the atmospheric plasma of a strongly magnetized neutron star. A resonance occurs when the effect of vacuum polarization...
Atmospheres and Spectra of Strongly Magnetized Neutron Stars (2001)
We construct atmosphere models for strongly magnetized neutron stars with surface fields $B\sim 10^{12}-10^{15}$ G and effective temperatures $T_{\rm eff}\sim 10^6-10^7$ K. The atmospheres directly...
Secular Bar-Mode Evolution and Gravitational Waves From Neutron Stars (2001)
The secular instability and nonlinear evolution of the m=2 f-mode (bar-mode) driven by gravitational radiation reaction in a rapidly rotating, newly formed neutron star are reviewed. There are two...
An accretion disk around a rotating magnetized star is subjected to magnetic torques which induce disk warping and precession. These torques arise from interactions between the stellar field and the...
Neutron Star Kicks and Asymmetric Supernovae (2000)
Observational advances over the last decade have left little doubt that neutron stars received a large kick velocity (of order a few hundred to a thousand km/s) at birth. The physical origin of the...
Matter in Strong Magnetic Fields (2000)
The properties of matter are significantly modified by strong magnetic fields, $B>>2.35\times 10^9$ Gauss ($1 G =10^{-4} Tesla$), as are typically found on the surfaces of neutron stars. In such...
Pulsar Jets: Implications for Neutron Star Kicks and Initial Spins (2000)
Lai, Dong, Chernoff, David F., Cordes, James M.
We study implications for the apparent alignment of the spin axes, proper-motions, and polarization vectors of the Crab and Vela pulsars. The spin axes are deduced from recent Chandra X-ray...
Global Nonradial Instabilities of Dynamically Collapsing Gas Spheres (2000)
Self-similar solutions provide good descriptions for the gravitational collapse of spherical clouds or stars when the gas obeys a polytropic equation of state, $p=K\rho^\gamma$ (with $\gamma\le...
Physics of Neutron Star Kicks (1999)
It is no longer necessary to `sell' the idea of pulsar kicks, the notion that neutron stars receive a large velocity (a few hundred to a thousand km s$^{-1}$) at birth. However, the origin of the...
R-Mode Oscillations and Spindown of Young Rotating Magnetic Neutron Stars (1999)
Recent work has shown that a young, rapidly rotating neutron star loses angular momentum to gravitational waves generated by unstable r-mode oscillations. We study the spin evolution of a young,...
Tidal Interaction between a Fluid Star and a Kerr Black Hole in Circular Orbit (1999)
We present a semi-analytic study of the equilibrium models of close binary systems containing a fluid star (mass $m$ and radius $R_0$) and a Kerr black hole (mass $M$) in circular orbit. We consider...
Growth of Perturbation in Gravitational Collapse and Accretion (1999)
When a self-gravitating spherical gas cloud collapses or accretes onto a central mass, the inner region of the cloud develops a density profile $\rho\propto r^{-3/2}$ and the velocity approaches...
Magnetically Driven Warping, Precession and Resonances in Accretion Disks (1999)
The inner region of the accretion disk onto a rotating magnetized central star (neutron star, white dwarf or T Tauri star) is subjected to magnetic torques which induce warping and precession of the...
Lai, Dong, Lovelace, Richard, Wasserman, Ira
It has recently been suggested that the maximum observed quasi-periodic oscillation (QPO) frequencies, $\nu_{max}$, for several low-mass X-ray binaries, particularly 4U 1820-30, correspond to the...
A Family of Gravitational Waveforms from Rapidly Rotating Neutron Stars (1999)
This note describes fitting formulae for the gravitational waveforms generated by a rapidly rotating neutron star (e.g., newly-formed in the core collapse of a supernova) as it evolves from an...
Dong Lai, Richard Lovelace, Ira Wasserman
It has recently been suggested that the maximum observed quasi-periodic oscillation (QPO) frequencies, νmax, for several low-mass X-ray binaries, particularly 4U 1820-30, correspond to the orbital...
Resonant Tidal Excitations of Rotating Neutron Stars in Coalescing Binaries (1998)
In a coalescing neutron star-neutron star (NS-NS) or neutron star-black hole (NS-BH) binary, oscillation modes of the NS can be resonantly excited by the companion during the final minutes of the...
We study neutrino-nucleon scattering and absorption in a dense, magnetized nuclear medium. These are the most important sources of neutrino opacity governing the cooling of a proto-neutron star in...
Secular Instability of g-Modes in Rotating Neutron Stars (1998)
Gravitational radiation tends to drive gravity modes in rotating neutron stars unstable. For an inviscid star, the instability sets in when the rotation frequency is about 0.7 times the corresponding...
Can Parity Violation in Neutrino Transport Lead to Pulsar Kicks? (1998)
In magnetized proto-neutron stars, neutrino cross sections depend asymmetrically on the neutrino momenta due to parity violation. However, these asymmetric opacities do not induce any asymmetric flux...
The original paper describes neutrino cooling calculations in the presence of asymmetric neutrino opacities due to parity violation in strong magnetic fields. In early April, through the work of P....
In proto-neutron stars with strong magnetic fields, the cross section for $\nu_e$ ($\bar\nu_e$) absorption on neutrons (protons) depends on the local magnetic field strength due to the quantization...
Parity Violation in Neutrino Transport and the Origin of Pulsar Kicks (1997)
In proto-neutron stars with strong magnetic fields, the neutrino-nucleon scattering/absorption cross sections depend on the direction of neutrino momentum with respect to the magnetic field axis, a...
Hydrogen Phases on the Surface of a Strongly Magnetized Neutron Star (1997)
The outermost layers of some neutron stars are likely to be dominated by hydrogen, as a result of fast gravitational settling of heavier elements. These layers directly mediate thermal radiation from...
Dynamical Tides in Rotating Binary Stars (1997)
We study the effect of rotation on the excitation of internal oscillation modes of a star by the external gravitational potential of its companion. Unlike the nonrotating case, there are difficulties...
Dynamics of PSR J0045-7319/B-star Binary and Neutron Star Formation (1997)
Recent timing observations have revealed the presence of orbital precession due to spin-orbit coupling and rapid orbital decay due to dynamical tidal interaction in the PSR J0045-7319/B-star binary...
We study how the neutron-star equation of state affects the onset of the dynamical instability in the equations of motion for inspiraling neutron-star binaries near coalescence. A combination of...
Tidal Stablization of Neutron Stars and White Dwarfs (1996)
What happens to a neutron star or white dwarf near its maximum mass limit when it is brought into a close binary orbit with a companion? Such situation may occur in the progenitors of Type Ia...
Recent timing observations of PSR J0045-7319 reveal that the neutron star/B star binary orbit is decaying on a time scale of $|\Porb/\dot\Porb|=0.5$ Myr, shorter than the characteristic age...
Hydrogen molecules in a superstrong magnetic field: Excitation levels (1996)
We study the energy levels of H2 molecules in a superstrong magnetic field (B≳10^12 G), typically found on the surfaces of neutron stars. The interatomic interaction potentials are calculated by a...
Hydrogen Molecules In Superstrong Magnetic Field: II. Excitation Levels (1995)
We study the energy levels of H$_2$ molecules in a superstrong magnetic field ($B\go 10^{12}$ G), typically found on the surfaces of neutron stars. The interatomic interaction potentials are...
Motion and Ionization Equilibrium of Hydrogen Atoms in Superstrong Magnetic Field (1995)
We study the effects of finite proton mass on the energy levels of hydrogen atoms moving transverse to a superstrong magnetic field $B$ with generalized pseudomomentum $K_\perp$. Field strengths of...
Superfluidity of Hydrogenlike Gas in a Strong Magnetic Field ? (1995)
The recent claim that in a strong magnetic field hydrogenlike gas (e.g., excitons in certain semiconductors, neutron star surface layers) becomes superfluid is refuted. Molecules form by strong...
Lai, Dong, Bildsten, Lars, Kaspi, Vicky
The spin-induced quadrupole moment of a rapidly rotating star changes the orbital dynamics in a binary system, giving rise to advance (or regression) of periastron and precession of the orbital...
Gravitational Radiation from Rapidly Rotating Nascent Neutron Stars (1994)
We study the secular evolution and gravitational wave signature of a newly-formed, rapidly rotating neutron star. The neutron star may arise from core collapse in a massive star or from the...
Hydrodynamics of Coalescing Binary Neutron Stars: Ellipsoidal Treatment (1994)
We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are...
Resonant Oscillations and Tidal Heating in Coalescing Binary Neutron Stars (1994)
Tidal interaction in a coalescing neutron star binary can resonantly excite the g-mode oscillations of the neutron star when the frequency of the tidal driving force equals the intrinsic g-mode...
Hydrodynamics of Rotating Stars and Close Binary Interactions: Compressible Ellipsoid Models (1994)
Lai, Dong, Rasio, Frederic A., Shapiro, Stuart L.
We develop a new formalism to study the dynamics of fluid polytropes in three dimensions. The stars are modeled as compressible ellipsoids and the hydrodynamic equations are reduced to a set of...