A model for disk accretion by a rotating magnetic neutron star is proposed which includes a detailed
NASA Technical Reports Server (NTRS)
They could see details as fine as the neutron star's accretion disk, a ring of gas swirling around and flowing onto the neutron star, as the disk buckled ...
NASA Website
Nuclear reactions in the hot accretion plasma surrounding a collapsed star are a source of neutrons,
A large number of neutron stars (NSs), approximately 10(exp 9), populate the Galaxy, but only a tiny
X-ray flashes from accreting neutron stars are considered. A number of possible explanations for the phenomenon are reviewed. A physical picture is drawn, and numerical models are discussed. 3 figures. (RWR)
Energy Citations Database
Jan 22, 2010 ... Many astrophysical objects, including neutron stars and accretion disks, are powered by a combination of very strong magnetic fields and ...
Radial oscillations resulting from axisymmetric perturbations in viscous accretion disks surrounding
I review the X-ray observations of galactic accreting black holes and neutron stars and interpretations of these in terms of solutions of the accretion flow equations. PMID:12804240
PubMed
Dec 31, 2008 ... The line widths are influenced by rotation of the star via the Doppler effect. Since the spin rates of many of these accreting neutron stars ...
Matter spirals toward the neutron star in the form of an accretion disk, a journey visible in X-ray radiation. In doing so, it transfers its orbital energy to the neutron ...
Abstract. The accretion process onto a magnetized isolated neutron star, which captures material from the interstellar medium, is discussed. The evolutionary track of such a star can be presented as a sequence of four states: ejector, supersonic propeller, subsonic propeller, andsteady accretor. Ishowthatsubsonic ...
E-print Network
opportunity to study rapid variations in stars that are very compact, like white dwarfs and neutron stars exotic neutron stars. How does accretion occur in binary stars? Two stars in orbit around each other up like compact ...
The basic ideas of accretion onto magnetized neutron stars are outlined. These are applied to a simple model of the structure of the plasma mound sitting at the magnetic poles of such a star, in which upward diffusion of photons is balanced by their downw...
National Technical Information Service (NTIS)
The kilohertz frequencies of QPOs from accreting neutron star systems imply that they are generated in regions of strong gravity, close to the star. This suggests that observations of the QPOs can be used to constrain the properties of neutron stars thems...
neutron stars would have important implications for nuclear and particle physics. While many of these objects are in binary systems ( X-ray binaries ), where ...
Feb 23, 2004 ... The gas spirals toward the neutron star like water going down a drain, forming what scientists call an accretion disk. ...
Accreting neutron stars can produce jets only if they are weakly magnetized (B ~ 108 G). On the other hand, neutron stars are compact objects born with strong surface magnetic fields (B ~ 1012 G). In this work we study the conditions for jet formation in a binary system formed by a ...
NASA Astrophysics Data System (ADS)
An initial study of the evolution of a neutron star in a close-binary orbit of high eccentricity discloses a special class of systems that will never achieve a state of pure, steady accretion: the neutron star will continually oscillate between an accreting state and a ...
The shape of the Alfven surface separating the magnetosphere of a neutron star from the stream of accreting plasma and the velocity and scattering optical depth of the gas layer flowing along the Alfven surface are calculated. Calculations are made both for spherically symmetrical fall of the gas and for disk ...
Spherically symmetric, time-dependent accretion of an ionized hydrogen plasma onto a neutron star is
Feb 23, 2004 ... "Accretion disks are known to flow around many objects in the universe ... Under normal conditions, accretion disks appear far too minute to ...
velocities and to magnetic #12;eld decay. 2 The Ejector, Propeller and Accretion Phases Over the stellar challenge. In Section 2 we trace the evolution of a neutron star in the Ejector, Propeller and Accretion close to their mass shedding threshold, a limit sensitive to the equation of state for nuclear matter
We consider the structure and emission spectra of nonthermal accretion disks around both strongly and weakly magnetized neutron stars. Such disks may be dissipating their gravitational binding energy and transferring their angular momentum via semicontinu...
A model for emission of the hard photons of gamma bursts is presented. The model assumes accretion at nearly the Eddington limited rate onto a neutron star without a magnetic field. Initially soft photons are heated as they are compressed between the accr...
A model for emission of the hard photons of gamma bursts is presented. The model assumes accretion at nearly the Eddington limited rate onto a neutron star without magnetic a field. Initially soft photons are heated as they are compressed between the accr...
X-ray bursters are considered to be neutron stars with a weak magnetic field that are undergoing disk-type accretion. If the field is weak enough, the disk will reach to the neutron star surface; next to the surface, a narrow boundary layer will develop, girdling the star. ...
thermonuclear flashes on accreting neutron stars are compared. ... An ignition mechanism of the bursts is proposed in terms of elemental mixing and ...
Mar 1, 2011 ... thermonuclear flashes on accreting neutron stars are compared. ... An ignition mechanism of the bursts is proposed in terms of elemental ...
Magnetic compact objects (neutron stars or white dwarfs) are currently thought to be present in many
It is shown here that the behavior of nuclear burning on accreting neutron stars depends on the mass
... the hard X-ray Galactic continuum could be the superposition of unresolved point sources such as accreting neutron stars or black holes. ...
DTIC Science & Technology
The current generation of gamma-ray telescopes (SIGMA, GRO) provides a new opportunity for observing
Neutron Stars, Pulsars, Millisecond Pulsars, and Gravitational Radiation: GLOSSARY. Accretion disk: The flattened, pancake-like structure formed by matter ...
Abstracts of individual items from the workshop were prepared separately for the data base. (ERA citation 08:044825)
of these phenomena, the one supported by the data is the following. Accreting black holes and neutron stars are observed to launch relativistic puffs of plasma:...
Science.gov Websites
Jan 13, 2011 ... High-resolution X-ray spectra of bursting, accreting neutron stars show redshifted absorption lines that reveal the neutron star mass and ...
A final report is given of two research projects dealing with magnetic fields of neutron stars. These are the modulation of thermal x-rays from cooling neutron stars and plasma instabilities in neutron star accretion columns. (DWL)
DOE Information Bridge
A final report is given of two research projects dealing with magnetic fields of neutron stars. These are the modulation of thermal x-rays from cooling neutron stars and plasma instabilities in neutron star accretion columns. (ERA citation 12:044375)
The magnetospheres of accreting compact stars (neutron stars and white dwarfs) are examined. It is assumed that the compact star possesses a multipole magnetic field. The shape of the magnetosphere for the two-dimensional analog of spherically symmetric accretion and the ...
accreting star. Roughly half the known X�ray novae contain BH candidates and the rest contain NSs. X of the accreting star. As discussed in the Introduction, the accretion rate in a typical X�ray nova spans a wide in which the compact accreting primary ...
The present conference considers topics in the fields of rotation-powered pulsars, the relationship of pulsars to SNRs, accretion-powered pulsars, neutron-star formation in theoretical SNs, neutrol stellar evolution, neutron star physics, and other manifestations of neutron ...
Highly nonstationary accretion onto a magnetized neutron star from a surrounding accretion disc is considered. Nonstationary accretion has been considered before in terms of droplets or rain or as a necessary consequence of instabilities in the accretion column flow. Here, ...
A model for emission of the hard photons of gamma bursts is presented. The model assumes accretion at nearly the Eddington limited rate onto a neutron star without magnetic a field. Initially soft photons are heated as they are compressed between the accreting matter and the star. A large ...
Important aspects of the theory of accretion are reviewed and the theory of the spherical accretion of a polytropic gas is presented. The effect of the termination of the flow at the surface of a neutron star or white dwarf is studied with consideration given to the interaction with a magnetic field anchored to the ...
The present study of hypercritical accretion flows onto neutron stars considers steady-state, spherically symmetric flows whose accretion rate range is characterized by the carrying away of gravitational-accretion energy by neutrinos. The models used encompass pair production, radiation ...
The X-ray properties of the main sequence Be stars conclude that they are a widely separated binary system containing an accreting neutron star.
Rare isotopes from the proton drip line to the neutron drip line are produced on the surface and crust of accreting neutron stars. Understanding their properties is essential to address the open questions raised by a variety of new observations of X-ray binaries, in particular X-ray bursters and transients. This ...
Pycnonuclear fusion processes take place at extreme density conditions of ?>10^10 g/cm^3, anticipated for the core of white dwarfs or the crust of neutron stars. A formalism was developed for predicting pycnonuclear reaction rates for neutron rich nuclei in the carbon to magnesium range. The reaction rates have been used to simulate ...
The central region of the Galaxy is considered and the density of stars and interstellar matter is estimated. The power owed to accretion by neutron stars is calculated for an r.m.s. velocity of ~160 km/s as from the virial theorem. An upper limit for the accretion luminosity at x-ray ...
Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have shown that the X-ray flux during thermonuclear X-ray bursts from accreting neutron stars is often strongly pulsed at frequencies as high as 620 Hz. We now know that these oscillations are produced by spin modulation of the thermonuclear flux from the ...
Pulsars with pulsation periods in the millisecond range are thought to be neutron stars that have acquired an extraordinarily short spin period through the accretion of stellar material spiraling down onto the neutron star from a nearby companion. Nearly all the angular momentum and most of the ...
Mar 1, 2010 ... Chandra has also revealed unexpected parallels between accretion onto pre-main sequence stars, white dwarfs, neutron stars, stellar-mass and ...
With the help of a very simple two-zone model we deomonstrate the possiblity of periodic thermal relaxation (limit cycle) oscillations in the helium burning envelope of accreting neutron stars. Physically reasonable model parameters can be chosen which yield agreement with the observed features of X-ray bursts. We suggest that this ...
Many accreting neutron stars do so intermittently; that is, the accretion ceases for long quiescent intervals. During the accretion outburst, reactions are induced in the crust by the continual accumulation of matter. These reactions heat the crust out of thermal equilibrium with the core, and ...
X�1 is the only neutron star x�ray nova in which we can mount a reasonable observing pro� gram of a delay between the x�ray and optical rise will allow the confirmation of the ADAF model in a neutron star with NO similar increase in accretion onto the neutron ...
Nucleosynthesis, on the surface of accreting neutron stars, produces a range of chemical elements. We perform molecular dynamics simulations of crystallization to see how this complex composition forms new neutron star crust. We find chemical separation, with the liquid ocean phase greatly ...
It is stated that as accreted material falls to the surface of a magnetized neutron star, like Cen X-3 or Her X-1, it is arrested by radiation pressure in such a manner that a hot, dense mound of nearly stationary gas protrudes above each magnetic pole. Energy released above the mound diffuses out as moderately hard x rays; ...
The basic theoretical ideas in the models of regularly pulsating X-ray sources are discussed, and put in relation to the observations. The topics covered include physics of the magnetosphere of an accreting neutron star, hydrodynamics of the accretion column, physical processes close to the surface of the ...
We calculate the rapid proton ( rp) capture process of hydrogen burning on the surface of an accreting neutron star with an updated reaction network that extends up to Xe, far beyond previous work. In both steady-state nuclear burning appropriate for rapidly accreting neutron ...
The aim of this work is to compare a neutron star with an accreted crust and one with a non-accreted crust, and estimate which one is potentially a better source of gravitational waves (i.e. can sustain a larger �mountain�). To do this we present a new formalism, and find that a ...
Millisecond pulsars, both during and after accretion, stand a class apart from the general pulsar population due to the much weaker field strength at their surface. The prevailing view is that accretion of matter on to a neutron star causes a decay of its magnetic field strength, as viewed by an external observer. ...
arXiv:astro-ph/9802348v127Feb1998 CONSTRAINTS ON NEUTRON STAR MATTER FROM KILOHERTZ QPOs F. K. LAMB discoveries made so far with the Rossi X-Ray Timing Explorer is that many accreting neutron stars with weak upper bounds on the masses and radii of neutron ...
The aim of this paper is to compare the two cases of an isolated neutron star, with a non-accreted crust, and that of an accreting neutron star, with an accreted crust, and try to estimate which one of the two would make a better source of gravitational ...
driving frequency matches the natural frequency of vertical motion, there is a vertical resonance and the plasma can be driven relatively far out of the disk plane. The natural frequency is just the vertical a b s t r a c t The kilohertz frequencies of QPOs from accreting neutron star systems imply
The nature of pulsars that exhibit quasi-periodic oscillations (QPOs) is discussed. It is shown how QPOs are produced by an interaction between the accretion disk surrounding a neutron star with the neutron star's magnetic field. The possible relationship between pulsars that exhibit ...
Jan 13, 2011 ... The neutron star surface will be probed via X-ray absorption spectroscopy: metals deposited at the surface via accretion provide spectroscopic ...
An analytic model of magnetic torques applied to an accreting neutron star is employed to evaluate the magnetic dipole moments of x-ray pulsars. A new type of close binary system containing a neutron star is suggested.
Dec 31, 2008 ... 2) Accretion also leads to thermonuclear X-ray bursts; brief but bright flashes of thermal X-ray radiation shining through the neutron star ...
Dec 31, 2008 ... The simulated spectrum of the early phases of the X-ray bursts from the accreting neutron star EXO 0748-676 using the Constellation-X (100 ...
Dec 31, 2008 ... It is known from observations of burst oscillations that some of these accreting neutron stars produce an X-ray hot spot during some X-ray ...
We calculate the temperature profiles of (thin) accretion disks around rapidly rotating neutron stars (with low surface magnetic fields), taking into account the full effects of general relativity. We then consider a model for the spectrum of the X-ray emission from the disk that is parameterized by the mass ...
Nuclear reactions, proceeding in the crust of an accreting neutron star, produce heat a few hundred meters below star's surface. This process of deep crustal heating is important for understanding the luminosity of soft x-ray transients in quiescence. We describe different models of deep crustal heating. We show ...
A neutron star in a binary system whose other component is a Wolf--Rayet star will undergo distinctive accretion. In such a system an x-ray pulsar could develop only under highly special conditions.
Jun 19, 2006 ... Long Term Intensity Variations in X-ray Binaries ... has led to a number of new insights into accretion onto magnetized neutron stars. ...
Aug 1, 1986 ... those of models of thermonuclear flashes on accreting neutron stars are ... An ignition mechanism of the bursts is proposed in terms of ...
A model of the object SS 433 is considered, in which the observed properties would result from supercritical disk accretion onto a neutron star possessing a strong magnetic field.
observed in the 650 - 1100 Hz range. Both QPO increased in frequency. together, maintaining a nearly constant frequency separation of about 363 Hz, ...
Accreting high magnetic field neutron stars are observed as X-ray pulsars. ... An examination of a power spectrum of the pulsed emission shows that the peak ...
Evidence is mounting that cataclysmic variables are weak sources of synchrotron emission. If true, it demonstrates that accretion powered interacting binaries produce such emission whether their primaries are white dwarfs, neutron stars, or black holes.
Mar 1, 2011 ... Inside the chamber, a spiral filament made of tungsten, tantalum, graphite, .... of neutron stars and of the accretion disk of black holes. ...
We study thermal states of transiently accreting neutron stars (with mean accretion rates dot {M} ~ 10-14-10-9 Msun yr-1) determined by the deep crustal heating of accreted matter sinking into stellar interiors. We formalize a direct correspondence of this problem to the problem of cooling ...
A tiny neutron star orbits incessantly around a massive star with a diameter a million times larger than its own. The high luminosity of the massive star drives a strong wind from its surface. The neutron star crashes through this wind at over 300 kilometers per second. The ...
NSDL National Science Digital Library
The investigations of advection-dominated accretion flows (ADAFs), with emphasis on applications to X-ray binaries containing black holes and neutron stars is presented. This work is now being recognized as the standard paradigm for understanding the vari...
This paper studies the hydrodynamical problem of normal modes of small adiabatic oscillations of relativistic barotropic thin accretion disks around black holes (and compact weakly magnetic neutron stars). Employing WKB techniques, we obtain the eigen fre...
The accretion of low-velocity (..nu..<300km/sec) stellar wind by neutron stars could be a nonsteady process and might be responsible for such phenomena as transient x-ray sources and x-ray bursters.
ries containing weakly magnetized neutron stars, and to recently suggested models of accretion-powered emission from anomalous X-ray pulsars. ...
In this letter we show that the observed gamma -ray luminosity can be produced by an accretion disc around a non-magnetic neutron star or low mass black hole in which the dominant dissipative process in the disc is due to magnetic fields. The shearing mot...
We examine whether the accretion of dark matter onto neutron stars could ever have any visible external effects. Captured dark matter which subsequently annihilates will heat the neutron stars, although it seems the effect will be too small to heat close neutron ...
Observations of neutron stars in low mass X-ray binaries give us an opportunity to probe nuclear physics of both proton rich and neutron rich nuclei. I will describe how observations of Type I X-ray bursts and cooling of neutron stars after long accretion outbursts ...
The neutron star crust, the 1 kilometer region on the surface composed of nuclei and superfluid neutrons, is the physical location of the majority of the phenomena observed in neutron stars. The composition of the crust is a fundamental input for the evolution of isolated and ...
The illumination of companion stars in very low mass X-ray binaries by various kinds of radiation from the neighborhood of the neutron star after accretion has terminated or during accretion is considered. If a neutron star's spun-up period ...
By means of the accretion induced magnetic field evolution model of neutron star in low mass X-ray binary, the star spin frequency evolution has been studied, and we find that the star spin frequency is almost independent of the mass accretion rate, initial magnetic field ...
Superbursts are rare thermonuclear flashes from accreting neutron stars that can only ignite in case of a sufficiently high temperature of the neutron star crust, which is heated during accretion. Most superbursts take place when the neutron ...
Superbursts are rare thermonuclear flashes from accreting neutron stars. One condition for ignition is a sufficiently high temperature of the neutron star crust, which is heated during accretion. Most superbursts take place when the neutron ...
I review attempts made to determine the properties of neutron stars. The focus is on the maximum mass that a neutron star can have, or, conversely, the minimum mass required for the formation of a black hole. There appears to be only one neutron star for which there is ...
Phase transitions can be triggered by a change of density profile in neutron stars as a result of spin-up caused by mass accretion from a companion star. Such a spin evolution is the pathway from old canonical pulsars to millisecond pulsars. A number of x-ray neutron stars ...
Accreting neutron stars are able to fuse nuclei in their atmospheres through exotic nuclear processes such as the rapid proton (rp) process. Continual accretion pushes the nuclear ashes of this process deeper into the crust, where the intense density and temperature lead to electron captures on these nuclei. We ...
