Constraints on neutron star models of gamma-burst sources from the Einstein Observatory

For years the theoretical models of neutron star formation and evolution had remained largely unconstrained by observation. Following the Einstein X-ray Observatory surveys of supernova remnants and pulsars, however, strict temperature limits were placed on many putative neutron stars. The Einstein search for additional objects in the class of supernova remnants with embedded pulsars has increased the number of such objects by two. For the four objects in this class, the surface temperature limits (see Table 1) provide meaningful logically sound constraints on the neutron star models. For the future, however, still better X-ray observations are needed, both to increase the number of objects available for study and to refine the spatial and spectral capabilities of the X-ray measurements.

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Neutrinos in Proto-neutron Star Models

Acta Physica Polonica B ◽

10.5506/aphyspolb.44.2389 ◽

2013 ◽

Vol 44 (11) ◽

pp. 2389

Author(s):

M. Pieńkos

Keyword(s):

Neutron Star ◽

Star Models ◽

Proto Neutron Star

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Einstein Observatory Limits on Neutron Star Surface Temperatures

The Origin and Evolution of Neutron Stars ◽

10.1007/978-94-009-3913-4_91 ◽

1987 ◽

pp. 457-457

Author(s):

F. R. Harnden

Keyword(s):

Neutron Star ◽

Surface Temperatures ◽

Star Surface ◽

Einstein Observatory

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Dynamical Stability of Neutron Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900007646 ◽

1971 ◽

Vol 46 ◽

pp. 341-345

Author(s):

G. Chanmugam ◽

M. Gabriel

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Neutron Stars ◽

Dynamical Stability ◽

Star Models

The Nemeth-Sprung equation of state is modified and used to obtain neutron star models. Contrary to the results of some authors it is found that neutron stars with central densities ≲ 1014 g cm-3 are dynamically stable. It is suggested that some pulsars may belong to this category of stars.

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Relativistic fluid spheres applicable to neutron star models

The Astrophysical Journal ◽

10.1086/156448 ◽

1978 ◽

Vol 224 ◽

pp. 993 ◽

Cited By ~ 6

Author(s):

P. G. Whitman ◽

R. W. Redding

Keyword(s):

Neutron Star ◽

Star Models ◽

Relativistic Fluid ◽

Fluid Spheres

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Rapidly Rotating Neutron Star Models: Erratum

The Astrophysical Journal ◽

10.1086/168509 ◽

1990 ◽

Vol 351 ◽

pp. 705 ◽

Cited By ~ 1

Author(s):

John L. Friedman ◽

James R. Ipser ◽

Leonard Parker

Keyword(s):

Neutron Star ◽

Star Models

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The Origin of the Enhanced Dissipation “α” in Accretion Discs and its Relation to Gamma Bursts

Symposium - International Astronomical Union ◽

10.1017/s0074180900161315 ◽

1987 ◽

Vol 125 ◽

pp. 546-546

Author(s):

Stirling A. Colgate

Keyword(s):

Neutron Star ◽

Energy Release ◽

Velocity Shear ◽

Accretion Discs ◽

Large Energy ◽

Necessary Condition ◽

Large Temperature ◽

Fluid Viscosity ◽

Convective Turbulence ◽

Gamma Burst

The source of the enhanced dissipation or “α” viscosity of Keplerian accretion discs is central in all putative mechanisms for large energy release by matter accreting onto condensed objects and for the basic mechanism of star formation. The circumstances of gamma burst formation on neutron stars suggest convective buoyancy as a necessary condition for the large α. This is because the total mass ≅ 1019 g necessary to supply the energy of a gamma burst derived from infall is a natural limit for the mass stored in a disc without α viscosity. This suggests that buoyancy driven convective turbulence is the source of the enhanced transport in disc evolution models (Shakura and Sunyaev 1973). In support of this conjecture we find that the maximum possible energy released by ideal friction operating on the velocity shear of a disc is twice that required to destabilize the angular momentum distribution of such a disc. The heat energy available from an α viscosity is twice that necessary to create α in the first place. Hence, a nonlinear instability–nonlinear to create convective turbulence and nonlinear to create shear viscosity heating–is sufficient to drive α. One characteristic that would prevent the formation of such an instability is degeneracy of the disc matter as it accumulates near a neutron star (Paczynski and Jaroszynski 1978). Degeneracy inhibits strong convection because a given energy release within degenerate matter results in a large temperature, and hence large energy transport without convection. Convection occurs in an accretion disc whenever the energy which is dissipated in the disc requires a superadiabatic temperature gradient for its radiative or conductive transport to the surface. Some gamma burst mechanisms require exactly such a mechanism as a degenerate disc close to the neutron star in the correct mass (≅ 1019 g), at the correct radius several times the neutron star radius, to supply gravitational energy for a gamma burst. The degenerate disc accumulates mass stably until the density is great enough that degenerate fluid viscosity evolves the disc into contact with the neutron star. The large energy released by velocity shear at contact heats the disc causing rapid evolution and a gamma burst.

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