摘要:

Following a summary of the basic principles of pulsar timing, we present a review of recent results from timing observations of relativistic binary pulsars. In particular, we summarize the status of timing observations of the much celebrated original binary pulsarPSR&hthinsp;B1913+16,draw attention to the recent confirmation of strong evidence for geodetic precession in this system, review the recent measurement of multiple post-Keplerian binary parameters forPSR&hthinsp;B1534+12,and describe the Parkes Multibeam survey, a major survey of the Galactic Plane which promises to discover new relativistic binary pulsar systems. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301558

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Gravitational radiation can drive a fluid instability in a rotating neutron star, causing it to spin down to slower rotation rates. This instability has been understood for the last quarter of a century. However, until recently is was never clear that the process would operate in astrophysical circumstances. The surprising discovery, due to Nils Andersson, that sluggish “ocean” currents (known to astronomers asr-modes) can be unstable at arbitrarily slow rotation rates has opened the door to a number of interesting applications in relativistic astrophysics. One exciting implication is that the instability may explain the spin rate of pulsars born with high angular velocity. It also may be possible to observe the gravitational radiation associated with these currents with an advanced version of LIGO. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301559

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Gravitational waves are the most relativistic of the predictions of general relativity, and yet are one of the last of its experimental predictions to be fulfilled. In this article, I review the nature of gravitational waves, the methods by which we hope to detect them, what we will learn from their detection, and the prospects for the field. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301560

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

I review the characteristic initial value problem, its implementation as a robust computational algorithm for a 4-dimensional vacuum space-time (the PITT NULL CODE) and its application to the calculation of gravitational waveforms emitted by black holes. I describe the potential applications of the code to the binary black hole problem, via Cauchy-characteristic matching or pure characteristic evolution. In particular, the event horizon is itself a characteristic hypersurface and can be treated by characteristic methods as a stand-alone object. This allows an analytic treatment of the intrinsic geometry of the event horizon for colliding black holes which produces the pair-of-pants horizon found in the numerical simulation of the head-on-collision of black holes and the initially toroidal event horizon found in the simulation of a collapsing, rotating cluster. Most previous studies of black hole formation and merger are restricted to the axisymmetric case. However, axisymmetric horizons, like the Schwarzschild horizon, are non-generic. When applied to anon-axisymmetric horizon, the characteristic approach reveals substantially new features. In particular, coalescing black holes generically go through a toroidal phase before they become spherical. In a bigger picture, this analytic model of the event horizon provides part of the data for a simulation of the space-time exterior to a binary merger by means of the null code. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301561

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Coalescing compact binaries have been pointed out as the most promising source of gravitational waves for kilometer-size interferometers such as LIGO. Gravitational wave signals are extracted from the noise in the detectors by matched filtering. This technique performs really well if ana prioritheoretical knowledge of the signal is available. The information known about the possible sources is used to construct a model of the expected waveforms (templates). A common assumption made when constructing templates for coalescing compact binaries is that the companions move in a quasi-circular orbit. Some scenarios, however, predict the existence of eccentric binaries. We investigate the loss in signal-to-noise ratio due to non-optimal filtering of eccentric signals and calculate the fitting factor associated with the matched filtering of eccentric signals by circular templates. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301562

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We report on our numerical implementation of fully relativistic hydrodynamics coupled to Einstein’s field equations in three spatial dimensions. We briefly review several steps in our code development, including our recasting of Einstein’s equations and several tests which demonstrate its advantages for numerical integrations. We outline our implementation of relativistic hydrodynamics, and present numerical results for the evolution of both stable and unstable Oppenheimer-Volkov equilibrium stars, which represent a very promising first test of our code. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301563

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The equation of state for matter with energy density above2x1014&hthinsp;g/cm3is parametrized with three regions, two with adiabatic equations of state and the third with a causal equation of state. Searching the parameter space under a stability constraint, we find the maximum mass for a non-rotating relativistic neutron star depends on the maximum allowed values of the adiabatic index parameters. The maximum mass as a function of adiabatic index can be rendered to good approximation by a rational quadratic. Selecting a generous upper bound on the adiabatic index, it appears very likely that the maximum mass is less than three solar masses. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301564

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Limits on the rates of mass-exchange and orbital angular momentum loss in a mass-conservative circular binary system evolving by loss of orbital angular momentum and Roche lobe overflow are derived. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301565

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

In some ranges of mass ratio and mass-radius exponent, it is shown that there are inconsistencies in Faulkner’s (1971) analytic model of a mass-conservative circular binary system that is evolving via the combined processes of mass exchange through Roche lobe overflow and emission of gravitational waves. These inconsistencies occur because of the use of an assumption that the time derivative of the Roche lobe radius is equal to that of the stellar radius. Consequently, his equations for the rate of mass exchange and orbital period variations are generally invalid. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301566

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

It is shown that if an asymptotically flat spacetime is asymptotically stationary, in the sense that£&xgr;gabvanishes at the rate∼t−3for asymptotically timelike vector field&xgr;a,and the energy-momentum tensor vanishes at the rate∼t−4,then the spacetime is an asymptotically Schwarzschild spacetime. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301567

出版商:AIP    

年代:1999

数据来源: AIP