arXiv subjects

Balázs Mikóczi

Publications and source records attributed to Balázs Mikóczi.

17 recordsLinked to original sources

arXiv2022

Spin dynamics of moving bodies in rotating black hole spacetimes

The dynamics of spinning test bodies, moving in rotating black hole (Kerr, Bardeen-like and Hayward-like) spacetimes, are investigated. In Kerr spacetime, all the spherical, zoom-whirl and unbound orbits are considered numerically. Along spherical orbits and for high spin, an amplitude modulation is found in the harmonic evolution of the spin precessional angular velocity, caused by the spin-curvature coupling. Along the discussed zoom-whirl and unbound orbits, the test body approaches the center so much that it passes through the ergosphere. Near and inside the ergosphere, the variation of the spin direction can be very rapid. The effects of the spin-curvature coupling is also investigated. The initial values are chosen such a way, that the body and its spin move in the equatorial plane of the coordinate space and of the comoving frame, respectively. Hence, a clear effect of the spin-curvature coupling is observed as the orbit and the spin vector leave the equatorial plane. Additional effects in the spin precessional angular velocity and in the evolution of the Boyer-Lindquist coordinate components of the spin vector is also considered. Finally, in case of different regular black holes, the spin-curvature coupling influences differently the orbit and the spin evolutions.

gr-qc↗

arXiv2021

Spin precession of binary neutron stars with magnetic dipole moments

Spin precession equations including the spin-orbit (SO), spin-spin (SS), quadrupole-monopole (QM) and magnetic dipole-magnetic dipole (DD) leading-order interactions are derived for compact binary systems in order to investigate the DD contribution in the orbit-averaged spin precession equations for binary neutron star systems neglecting the gravitational radiation-reaction effect. It is known that the magnitudes of spins are not conserved quantities due to the DD interaction. We give a simple analytical description for the pure DD interaction making the magnitudes of spins almost constant by neglecting the SO, SS and QM contributions. We also demonstrate the evolutions of the relative angles of spins and magnetic dipoles with the help of numeric simulations including all contributions (SO, SS, QM and DD) and introduce a dimensionless magnetic dipole parameter to characterize the strength of magnetic fields for some realistic neutron star binaries. We find that for realistic configurations the strong magnetic fields of neutron stars can modify the spin dynamics over long periods of time.

gr-qc↗

arXiv2017

Spin supplementary conditions for spinning compact binaries

We consider different spin supplementary conditions (SSC) for a spinning compact binary with the leading-order spin-orbit (SO) interaction. The Lagrangian of the binary system can be constructed but it is acceleration-dependent in two cases of SSC. We rewrite the generalized Hamiltonian formalism proposed by Ostrogradsky and compute the conserved quantities and the dissipative part of relative motion during the gravitational radiation of each SSC. We give the orbital elements and observed quantities of the SO dynamics, for instance the energy and the orbital angular momentum losses and waveforms and discuss their SSC dependence.

gr-qc↗

arXiv2015

Eccentric first post-Newtonian waveforms for compact binaries in frequency domain with Hansen coefficients

The inspiral and merger of supermassive black hole binary systems with high orbital eccentricity are among the promising sources of the advanced gravitational wave observatories. In this paper we derive analytic ready-to-use first post-Newtonian eccentric waveform in Fourier domain with the use of Hansen coefficients. Introducing generic perturbations of celestial mechanics we have generalized the Hansen expansion to the first post-Newtonian order which are then used to express the waveforms. Taking into account the high eccentricity of the orbit leads to the appearance of secular terms in the waveform which are eliminated with the introduction of a phase shift. The waveforms have a systematic structure and as our main result these are expressed in a tabular form.

gr-qc↗

arXiv2012

Parameter estimation for inspiraling eccentric compact binaries including pericenter precession

Inspiraling supermassive black hole binary systems with high orbital eccentricity are important sources for space-based gravitational wave (GW) observatories like the Laser Interferometer Space Antenna (LISA). Eccentricity adds orbital harmonics to the Fourier transform of the GW signal and relativistic pericenter precession leads to a three-way splitting of each harmonic peak. We study the parameter estimation accuracy for such waveforms with different initial eccentricity using the Fisher matrix method and a Monte Carlo sampling of the initial binary orientation. The eccentricity improves the parameter estimation by breaking degeneracies between different parameters. In particular, we find that the source localization precision improves significantly for higher-mass binaries due to eccentricity. The typical sky position errors are $\sim1 $deg for a nonspinning, $10^7\,M_{\odot}$ equal-mass binary at redshift $z=1$, if the initial eccentricity 1 yr before merger is $e_0\sim 0.6$. Pericenter precession does not affect the source localization accuracy significantly, but it does further improve the mass and eccentricity estimation accuracy systematically by a factor of 3--10 for masses between $10^6$ and $10^7\,M_{\odot}$ for $e_0 \sim 0.3$.

gr-qc↗

arXiv2010

Secular momentum transport by gravitational waves from spinning compact binaries

We present a closed system of coupled first order differential equations governing the secular linear momentum loss of a compact binary due to emitted gravitational waves, with the leading order relativistic and spin-orbit perturbations included. In order to close the system, the secular evolution equations of the linear momentum derived from the dissipative dynamics are supplemented with the secular evolutions of the coupled angular variables, as derived from the conservative dynamics.

gr-qc↗

arXiv2009

Renormalized spin coefficients in the accumulated orbital phase for unequal mass black hole binaries

We analyze galactic black hole mergers and their emitted gravitational waves. Such mergers have typically unequal masses with mass ratio of the order 1/10. The emitted gravitational waves carry the inprint of spins and mass quadrupoles of the binary components. Among these contributions, we consider here the quasi-precessional evolution of the spins. A method of taking into account these third post-Newtonian (3PN) effects by renormalizing (redefining) the 1.5 PN and 2PN accurate spin contributions to the accumulated orbital phase is developed.

gr-qc↗

arXiv2009

Renormalized 2PN spin contributions to the accumulated orbital phase for LISA sources

We give here a new third post-Newtonisn (3PN) spin-spin contribution (in the PN parameter $ε$) to the accumulated orbital phase of a compact binary, arising from the spin-orbit precessional motion of the spins. In the equal mass case this contribution vanishes, but LISA sources of merging supermassive binary black holes have typically a mass ratio of 1:10. For such non-equal masses this 3PN correction is periodic in time, with period approximately $ε^{-1}$ times larger than the period of gravitational waves. We derive a renormalized and simpler expression of the spin-spin coefficient at 2PN, as an average over the time-scale of this period of the combined 2PN and 3PN contribution. We also find that for LISA sources the quadrupole-monopole contribution to the phase dominates over the spin-spin contribution, while the self-spin contribution is negligible even for the dominant spin. Finally we define a renormalized total spin coefficient $\barσ$ to be employed in the search for gravitational waves emitted by LISA sources.

gr-qc↗

arXiv2007

Orbital phase in inspiralling compact binaries

We derive the rate of change of the mean motion up to the second post-Newtonian order for inspiralling compact binaries with spin, mass quadrupole and magnetic dipole moments on eccentric orbits. We give this result in terms of orbital elements. We also present the related orbital phase for circular orbits.

gr-qc↗

arXiv2006

The second post-Newtonian order generalized Kepler equation

The radial component of the motion of compact binary systems composed of neutron stars and/or black holes on eccentric orbit is integrated. We consider all type of perturbations that emerge up to second post-Newtonian order. These perturbations are either of relativistic origin or are related to the spin, mass quadrupole and magnetic dipole moments of the binary components. We derive a generalized Kepler equation and investigate its domain of validity, in which it properly describes the radial motion.

gr-qc↗

arXiv2006

Generalized eccentric vs. true anomaly parametrizations in the perturbed Keplerian motion

The angular and the radial parts of the dynamics of the perturbed Kepler motion are separable in many important cases. In this paper we study the radial motion and its parametrizations. We develop in detail a generalized eccentric anomaly parametrization and a procedure of computing a generic class of integrals based on the residue theorem. We apply the formalism to determine various contributions to the luminosity of a compact binary.

astro-ph↗

arXiv2006

Kepler Equation for the Compact Binaries under the Spin-spin Interaction

In this work we consider compact binaries on eccentric orbit under the spin-spin interaction. Using the post-Newtonian formalism, the binaries undergo a perturbed Keplerian motion. Here we investigate only the radial motion and derive the contribution of the second post-Newtonian order spin-spin effect to the solution.

astro-ph↗

arXiv2006

Frequency Evolution of the Gravitational Waves for Compact Binaries

We present here a complete list of contributions to the gravitational wave frequency evolution from compact binaries on circular orbits up to the second post-Newtonian order by including the interaction of magnetic dipole moments, quadrupole-monopole interactions together with the spin-orbit, the spin-spin and the self-interaction spin contributions. We apply our results to the Manchester et al. model of the J0737-3039A-B double pulsar.

astro-ph↗

arXiv2006

An Efficient Method for the Evaluation of Secular Effects in the Perturbed Keplerian Motion

Binary systems subject to generic perturbations evolve on quasiperiodic orbits. We derive the most generic class of perturbations, which allow to evaluate secular effects via generalized complex true and eccentric anomaly parameters, by use of the residue theorem. Such perturbations include both the generic Brumberg force and various linear contributions to the conservative dynamics of compact binaries, up to the second post-Newtonian order. As an example, we compute the self-spin contribution to the luminosity due to gravitational radiation of a compact binary consisting of galactic black holes, the most important type of source for LISA. This translates to simply calculate the residue of the instantaneous energy loss in the origin of the complex parameter plane, which illustrates the power of the presented method.

astro-ph↗

arXiv2006

Self interaction of spins in binary systems

Beyond point mass effects various contributions add to the radiative evolution of compact binaries. We present all the terms up to the second post-Newtonian order contributing to the rate of increase of gravitational wave frequency and the number of gravitational wave cycles left until the final coalescence for binary systems with spin, mass quadrupole and magnetic dipole moments, moving on circular orbit. We evaluate these contributions for some famous or typical compact binaries and show that the terms representing the self interaction of individual spins, given for the first time here, are commensurable with the proper spin-spin contributions for the recently discovered double pulsar J0737-3039.

gr-qc↗

arXiv2005

The Kepler equation for inspiralling compact binaries

Compact binaries consisting of neutron stars / black holes on eccentric orbit undergo a perturbed Keplerian motion. The perturbations are either of relativistic origin or are related to the spin, mass quadrupole and magnetic dipole moments of the binary components. The post-Newtonian motion of such systems decouples into radial and angular parts. We present here for the first time the radial motion of such a binary encoded in a generalized Kepler equation, with the inclusion of all above-mentioned contributions, up to linear order in the perturbations. Together with suitably introduced parametrizations, the radial motion is solved completely.

astro-ph↗

arXiv2005

Self-interaction spin effects in inspiralling compact binaries

Gravitational radiation drives compact binaries through an inspiral phase towards a final coalescence. For binaries with\textit{spin, mass quadrupole and magnetic dipole moments}, various contributions add to this process, which is characterized by the rate of increase $df/dt$ of the gravitational wave frequency and the accumulated number $\mathcal{N}$ of gravitational wave cycles. We present here all contributions to $df/dt$ and $% \mathcal{N}$ up to the second post-Newtonian order. Among them we give for the first time the contributions due to the \textit{self-interaction of individual spins}. These are shown to be commensurable with the proper spin-spin contributions for the recently discovered J0737-3039 double pulsar, and argued to represent the first corrections to the radiation reaction in the Lense-Thirring approach.

astro-ph↗