Gravitomagnetism and pulsar beam precession near a Kerr black hole (original) (raw)

Frame Dragging and Other Precessional Effects in Black Hole Pulsar Binaries

The Astrophysical Journal, 1999

For radio pulsars in orbit with a compact companion, pulsar timing observations have proved to be a powerful tool for identifying the physical nature of the companion. Unfortunately, perhaps the most intriguing system where such a tool could be used, a pulsar in orbit with a black hole, has yet to be discovered. In this paper we give a detailed investigation of what one can learn about the black hole companion via timing observations of the pulsar. We present an analytic calculation for the propagation delay caused by the frame-dragging effect and show that it has the same functional behavior as the modulation of the observed rotational phase of the pulsar caused by the deflection of the radio signals in the gravitational field of the companion (bending delay). Thus, contrary to statements of other authors, the frame-dragging delay is unlikely to be separately measurable in pulsar binaries where the companion is a stellar mass black hole. We demonstrate, however, that the precession of the binary orbit caused by the relativistic spin-orbit coupling can lead to observable effects which can be used to set a lower limit to the black-hole spin, or possibly allow the determination of its magnitude and orientation. We give parameter estimates for two possible systems, a 10M black hole in orbit either with a young (∼ 0.1 s) pulsar or with a millisecond pulsar. Finally, we discuss the measurability of the quadrupole moment of the rotating black hole companion which would test the presence of a Kerr black hole. As an interesting side result of our calculations, we can give a further argument why the companion of PSR J0045-7319 cannot be a Kerr black hole.

Radio emission from a pulsar’s magnetic pole revealed by general relativity

Science, 2019

Binary pulsars are affected by general relativity (GR), causing the spin axis of each pulsar to precess. We present polarimetric radio observations of the pulsar PSR J1906+0746 that demonstrate the validity of the geometrical model of pulsar polarization. We reconstruct the (sky-projected) polarization emission map over the pulsar’s magnetic pole and predict the disappearance of the detectable emission by 2028. Two tests of GR are performed using this system, including the spin precession for strongly self-gravitating bodies. We constrain the relativistic treatment of the pulsar polarization model and measure the pulsar beaming fraction, with implications for the population of neutron stars and the expected rate of neutron star mergers.

Light-curve models for a pulsar orbiting a Kerr black hole

Monthly Notices of the Royal Astronomical Society, 1997

We have studied the signal received by a distant observer from a pulsar orbiting a stellar black hole. The binary system has a non-eccentric orbit and the most favourable configuration (edge-on) for observing the influence of the black hole on the signal emitted by the pulsar. In particular, the influence of the spin of the black hole on the observed signal and the possibility of determining the spin are examined in detail. In the case of quasi-coalescent binary systems, with an initial separation of ~0.01 light-seconds, the flux-time relation is different for a non-rotating black hole from that for a black hole with an extreme rotation velocity. The observational data obtained during the short lifetime of a quasi-coalescent system (< 3 h) could be matched with realistic theoretical profiles, which will be sensitive to the specific spin of the black hole. In the case of binary systems with an initial separation of ~ 10 light-seconds, the probability of measuring the specific spin is briefly discussed on the basis of the signal travelling in the surroundings of the black hole, which is strongly affected by the rotation.

A study of the gravitational wave pulsar signal with orbital and spindown effects1

2000

In this work, we present an analytic and a preliminary numerical analysis of the gravitational wave signal from a pulsar that includes simple spindown effects. We estimate the phase corrections to a monochromatic source signal due to rotational and elliptical orbital motion of the Earth, and perturbations due to Jupiter and the Moon. We briefly discuss the Fourier transform of

On gravitomagnetic precession around black holes

Monthly Notices of the Royal Astronomical Society, 1999

We compute exactly the frequency of Lense-Thirring precession for point masses in the Kerr metric, for arbitrary black hole mass and specific angular momentum. We show that this frequency, for point masses at or close to the innermost stable orbit, and for holes with moderate to extreme rotation, is less than, but comparable to the rotation frequency. Thus, if the quasi-periodic oscillations observed in the modulation of the Xray flux from some black holes candidates, BHCs, are due to Lense-Thirring precession of orbiting material, we predict that a separate, distinct QPO ought to be observed in each object.

A study of the gravitational wave pulsar signal with orbital and spindown effects

Canadian Journal of Physics, 2006

In this work we present analytic and numerical treatments of the gravitational wave signal from a pulsar which includes spindown. We consider phase corrections to a received monochromatic signal due to rotational and elliptical orbital motion of the Earth, as well as perturbations due to Jupiter and the Moon. We discuss the Fourier transform of such a signal, which is expressed in terms of well known special functions and lends itself to a tractable numerical analysis.

Black hole spacetimes and pulsar timing

2009

A pulsar in a relativistic orbit around a supermassive black hole will exhibit potentially observable strong field effects in the times of arrival of its pulses. We present a simple formalism for computing these effects. This formalism is applied to illustrate the several types of strong field effects, to give explicit examples for the simple case of equatorial pulse beaming

Long-term timing of millisecond pulsars and gravitational wave detection

Arxiv preprint arXiv:0906.4246, 2009

This thesis presents the results from a long-term timing campaign on 20 millisecond pulsars (MSPs). The stability of these pulsars is analysed in order to allow assessment of gravitational wave (GW) detection efforts through pulsar timing. In addition, we present a new method of limiting the amplitude of a stochastic background of GWs and derive a strong limit from applying this method to our data.

Lense-Thirring precession in strong gravitational fields

2012

The exact frame-dragging (or Lense-Thirring (LT) precession) rates for Kerr, Kerr-Taub-NUT (KTN) and Taub-NUT spacetimes have been derived. Remarkably, in the case of the 'zero angular momentum' Taub-NUT spacetime, the frame-dragging effect is shown not to vanish, when considered for spinning test gyroscope. In the case of the interior of the pulsars, the exact framedragging rate monotonically decreases from the center to the surface along the pole and but it shows an 'anomaly' along the equator. Moving from the equator to the pole, it is observed that this 'anomaly' disappears after crossing a critical angle. The 'same' anomaly can also be found in the KTN spacetime. The resemblance of the anomalous LT precessions in the KTN spacetimes and the spacetime of the pulsars could be used to identify a role of Taub-NUT solutions in the astrophysical observations or equivalently, a signature of the existence of NUT charge in the pulsars.