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in subjects: "Neutron Stars"

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Time-Dependent Two-Dimensional Radiation Hydrodynamics of Accreting Matter Onto Highly Magnetized Neutron Stars

We present for the first time, the self-consistent solution of the two-dimensional, time-dependent equations of radiation-hydrodynamics governing the accretion of matter onto the highly magnetized polar caps of luminous x-ray pulsars. The calculations show a structure in the accretion column very different from previous one-zone uniform models. We have included all the relevant magnetic field corrections to both the hydrodynamics and the radiative transport. We include a new theory for the diff… more

Date: November 24, 1989

Creator: Klein, R.I. (California Univ., Los Angeles, CA (USA). Dept. of Astronomy Lawrence Livermore National Lab., CA (USA) California Univ., Los Angeles, CA (USA). Inst. of Geophysics and Planetary Physics) & Arons, J. (California Univ., Berkeley, CA (USA). Dept. of Astronomy California Univ., Los Angeles, CA (USA). Inst. of Geophysics and Planetary Physics CEA Centre d'Etudes Nucleaires de Saclay, 91 -

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Strange-quark-matter stars

We investigate the implications of rapid rotation corresponding to the frequency of the new pulsar reported in the supernovae remnant SN1987A. It places very stringent conditions on the equation of state if the star is assumed to be bound by gravity alone. We find that the central energy density of the star must be greater than 13 times that of nuclear density to be stable against the most optimistic estimate of general relativistic instabilities. This is too high for the matter to consist of i… more

Date: November 1, 1989

Creator: Glendenning, N. K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Neutron star formation in theoretical supernovae. Low mass stars and white dwarfs

The presupernova evolution of stars that form semi-degenerate or strongly degenerate O + Ne + Mg cores is discussed. For the 10 to 13 Msub solar stars, behavior of off-center neon flashes is crucial. The 8 to 10 m/sub solar stars do not ignite neon and eventually collapse due to electron captures. Properties of supernova explosions and neutron stars expected from these low mass progenitors are compared with the Crab nebula. The conditions for which neutron stars form from accretion-induced coll… more

Date: January 1, 1986

Creator: Nomoto, K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Thermonuclear model for x-ray transients

The thermonuclear evolution of a 1.41 M sub solar neutron star accreting both solar and metal-deficient mixtures of hydrogen, helium, and heavy elements at rates ranging from about 10/sup -11/ to 10/sup -10/ M sub solar per year is examined using a one-dimensional numerical model. The metal deficient compositions may result either from placement of the neutron star in a binary system with a Population II red giant or from gravitational settling of heavy ions in the accreted material. For such a… more

Date: January 1, 1982

Creator: Wallace, R. K.; Woosley, S. E. & Weaver, T. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Presupernova evolution of massive stars

Population I stars of 15 M/sub mass/ and 25 M/sub mass/ have been evolved from the zero-age main sequence through iron core collapse utilizing a numerical model that incorporates both implicit hydrodynamics and a detailed treatment of nuclear reactions. The stars end their presupernova evolution as red supergiants with photospheric radii of 3.9 x 10/sup 13/ cm and 6.7 x 10/sup 13/ cm, respectively, and density structures similar to those invoked to explain Type II supernova light curves on a st… more

Date: December 15, 1977

Creator: Weaver, T. A.; Zimmerman, G. B. & Woosley, S. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Fate of accreting white dwarfs: Type I supernovae vs collapse

The final fate of accreting C + O white dwarfs is either thermonuclear explosion or collapse, if the white dwarf mass grows to the Chandrasekhar mass. We discuss how the fate depends on the initial mass, age, composition of the white dwarf and the mass accretion rate. Relatively fast accretion leads to a carbon deflagration at low central density that gives rise to a Type Ia supernova. Slower accretion induces a helium detonation that could be observed as a Type Ib supernova. If the initial mas… more

Date: January 1, 1986

Creator: Nomoto, Ken'ichi

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Research in nuclear astrophysics: Stellar collapse and supernovae

This progress report describes the nuclear astrophysics research activities in the Earth and Space Sciences Department at Stony Brook during the last year. Our research focused on three aspects of nuclear astrophysics: (1) the equation of state of hot, dense matter, (2) the origin of supernovae and neutron stars, (3) the early cooling epoch of neutron stars. The following contains detailed reports which summarize each completed project.

Date: January 1, 1992

Creator: Lattimer, J.M. & Yahil, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Critical study of type II supernovae: equations of state and general relativity

The relevance of relativistic gravitation and of the properties of nuclear matter at high density to supernova explosions is examined in detail. The existing empirical knowledge on the nuclear equation of state at densities greater than saturation, extracted from analysis of heavy ion collisions and from the breathing mode in heavy nuclei, is also considered. Particulars of the prompt explosions recently obtained theoretically by Baron, Cooperstein, and Kahana are presented. 40 refs., 9 figs., … more

Date: January 1, 1986

Creator: Kahana, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Hyperons in neutron stars

Generalized beta equilibrium involving nucleons, hyperons, and isobars is examined for neutron star matter. The hyperons produce a considerable softening of the equation of state. It is shown that the observed masses of neutron stars can be used to settle a recent controversy concerning the nuclear compressibility. Compressibilities less than 200 MeV are incompatible with observed masses. 7 refs., 9 figs.

Date: April 1, 1986

Creator: Glendenning, N.K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Collapse of accreting carbon-oxygen white dwarfs induced by carbon deflagration at high density

A critical condition is obtained for which carbon deflagration induces collapse of an accreting C + O white dwarf, not explosion. If the carbon deflagration is initiated at central density as high as 10/sup 10/ g cm/sup -3/ and if the propagation of the deflagration wave is slower than approx. 0.15 upsilon/sub s/ (upsilon/sub s/ is the sound speed), electron capture behind the burning front induces collapse to form a neutron star. This is the case for both conductive and convective deflagration… more

Date: January 1, 1986

Creator: Nomoto, K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Variational theory of nuclear and neutron matter

In these lectures we will discuss attempts to solve the A = 3 to {infinity} nuclear many-body problems with the variational method. We choose the form of a variational wave function {Chi}{sub v}(1, 2{hor ellipsis}A) to describe the ground state. The {Chi}{sub v} and the ground-state energy E{sub v} are obtained by minimizing E{sub v} = {l angle}{Chi}{sub v}{vert bar}H{vert bar}{Chi}{sub v}{r angle}/{l angle}{Chi}{sub v}{vert bar}{Chi}{sub v}{r angle} with respect to variations in {Chi}{sub v}. … more

Date: June 1, 1989

Creator: Pandharipande, V.R.; Wiringa, R.B. (Illinois Univ., Urbana, IL (USA). Dept. of Physics & Argonne National Lab., IL (USA))

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Supernovae, compact stars and nuclear physics

We briefly review the current understanding of supernova. We investigate the implications of rapid rotation corresponding to the frequency of the new pulsar reported in the supernovae remnant SN1987A. It places very stringent conditions on the equation of state if the star is assumed to be bound by gravity alone. We find that the central energy density of the star must be greater than 12 times that of nuclear density to be stable against the most optimistic estimate of general relativistic inst… more

Date: August 25, 1989

Creator: Glendenning, N.K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Quark core stars, quark stars and strange stars

A recent one flavor quark matter equation of state is generalized to several flavors. It is shown that quarks undergo a first order phase transition. In addition, this equation of state depends on just one parameter in the two flavor case, two parameters in the three flavor case, and these parameters are constrained by phenomenology. This equation of state is then applied to the hadron-quark transition in neutron stars and the determination of quark star stability, the investigation of strange … more

Date: January 1, 1988

Creator: Grassi, F.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Neutrino emission by the pair, plasma, and photo processes in the Weinberg-Salam model

The results of numerical integrations of the rates and emissivities of the photo, pair, and plasma neutrino emission mechanisms in the Weinberg-Salam theory of the weak interaction are presented. The range of densities 10 gm cm/sup -3/ less than or equal to rho < 10/sup 14/ gm cm/sup -3/ and the temperature range 10/sup 8/K less than or equal to T less than or equal to 10/sup 11/K are considered. Fitting formulae, similar to those provided by Beaudet, Petrosian, and Salpeter, which reproduce th… more

Date: June 1, 1986

Creator: Schinder, P. J.; Schramm, D. N.; Witta, P. J.; Margolis, S. H. & Tubbs, D. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Spectral modelling of the soft gamma ray repeater

This paper summarizes the results of numerical modelling of the spectra of the soft gamma ray repeater (SGR 1806-20). Parameters of the emission region can be extracted from the spectral fits under the simplistic assumption of isothermal and homogeneous emission layers. Limits on the luminosity distance of the source can also be derived if we make specific interpretations of the low frequency turnover in the observed spectrum. 12 refs., 3 figs.

Date: February 1, 1988

Creator: Liang, E.P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Rapid cooling and structure of neutron stars

This report discusses the following topics on neutron stars: direct URCA neutrino emission; thermal evolution models; analytic model for diffusion through the crust; and core superfluidity. (LSP).

Date: January 1, 1992

Creator: Van Riper, Kenneth A. & Lattimer, James M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The Neutrino Process and Neutrino R-Process

Almost all of the 3 {center dot} 10{sup 53} ergs released in a core-collapse supernova is carried off by the neutrinos emitted from the cooling neutron star. These neutrinos can excite nuclei in the mantle of the star by their neutral and charged current reactions, leading to the spallation of nucleonsa and {alpha}-particles and the production of new daughter nuclei, I will describe rather detailed network calculations that suggest this neutrino process'' is an important nucleosynthesis mechani… more

Date: January 1, 1991

Creator: Haxton, W. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Nuclear and particle astrophysics

We discuss the physics of matter that is relevant to the structure of compact stars. This includes nuclear, neutron star matter and quark matter and phase transitions between them. Many aspects of neutron star structure and its dependance on a number of physical assumptions about nuclear matter properties and hyperon couplings are investigated. We also discuss the prospects for obtaining constraints on the equation of state from astrophysical sources. Neuron star masses although few are known a… more

Date: October 31, 1990

Creator: Glendenning, N.K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Hadron-quark phase transition in dense stars

An equation of state is computed for a plasma of one flavor quarks interacting through some phenomenological potential, at zero temperature. Assuming that the confining potential is scalar and color-independent, it is shown that the quarks undergo a first-order mass phase transition. In addition, due to the way screening is introduced, all the thermodynamic quantities computed are independent of the actual shape of the interquark potential. This equation of state is then generalized to a severa… more

Date: October 1, 1987

Creator: Grassi, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Theoretical calculation of rapid x-ray transients and radius expansion

We present a calculation of a thermonuclear runaway on a 10 km neutron star which produces two x-ray bursts separated by approx. 2500 sec.

Date: July 1983

Creator: Starrfield, S.; Sparks, W.; Truran, J. & Kenyon, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A Look at Supernova 1987A

Supernova 1987A is reviewed with emphasis on the neutrino observations. It is shown that the results fit well with the expectations for neutrino temperatures (T approx. 4epsilon/sub 0/4.5 MeV) and total energy emitted (2epsilon/sub 0/4 x 10/sup 53/ ergs). It is argued that the detection tends to favor collapse models that yield emission for 10 second timescales with a 1epsilon/sub 0/2 second early accretion phase followed by Kelvin-Helmholtz cooling as opposed to prompt shocks with the immediat… more

Date: October 1, 1987

Creator: Schramm, D. N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Experimental astrophysics with high power lasers and Z pinches

With the advent of high energy density (HED) experimental facilities, such as high-energy lasers and fast Z-pinch, pulsed-power facilities, mm-scale quantities of matter can be placed in extreme states of density, temperature, and/or velocity. This has enabled the emergence of a new class of experimental science, HED laboratory astrophysics, wherein the properties of matter and the processes that occur under extreme astrophysical conditions can be examined in the laboratory. Areas particularly … more

Date: December 10, 2004

Creator: Remington, B. A.; Drake, R. P. & Ryutov, D. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Investigating High Field Gravity using Astrophysical Techniques

The purpose of these lectures is to introduce particle physicists to astrophysical techniques. These techniques can help us understand certain phenomena important to particle physics that are currently impossible to address using standard particle physics experimental techniques. As the subject matter is vast, compromises are necessary in order to convey the central ideas to the reader. Many general references are included for those who want to learn more. The paragraphs below elaborate on the … more

Date: February 1, 2008

Creator: Bloom, Elliott D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Experimental measurements of the 15O(alpha,gamma)19Ne reaction rate and the stability of thermonuclear burning on accreting neutron stars

Neutron stars in close binary star systems often accrete matter from their companion stars. Thermonuclear ignition of the accreted material in the atmosphere of the neutron star leads to a thermonuclear explosion which is observed as an X-ray burst occurring periodically between hours and days depending on the accretion rate. The ignition conditions are characterized by a sensitive interplay between the accretion rate of the fuel supply and its depletion rate by nuclear burning in the hot CNO c… more

Date: May 8, 2007

Creator: Fisker, J.; Tan, W.; Goerres, J.; Wiescher, M. & Cooper, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department