Probing Ultralight Bosons with Compact Eccentric Binaries

Ultralight bosons can be abundantly produced through superradiance process by a spinning black hole and form a bound state with hydrogen-like spectrum. We show that such a gravitational atom typically possesses anomalously large mass quadrupole and leads to significant orbital precession when it forms an eccentric binary with a second compact object. Dynamically formed black hole binaries or pulsar-black hole binaries are typically eccentric during their early inspirals. We show that the large orbital precession can generate distinct and observable signature in their gravitational wave or pulsar timing signals.

Detection of Volatiles from Raw Beef Meat from Different Packaging Systems Using Solid-Phase Microextraction GC–Accurate Mass Spectrometry

The volatile profile of raw beef contains vital information related to meat quality and freshness. This qualitative study examines the effect of packaging system on the formation and release of volatile organic compounds (VOCs) from raw beef over time, relative to the packaging best before date (BBD). The three packaging systems investigated were modified atmospheric packaging, vacuum packaging, and cling-wrapped packaging. Porterhouse steak samples with the same BBD were analysed from 3 days before to 3 days after the BBD. VOCs were detected via preconcentration using solid-phase microextraction combined with gas chromatography–accurate mass quadrupole time-of-flight mass spectrometry. In total, 35 different VOCs were tentatively identified. Interestingly, there was no clear relationship of the VOCs detected between the three packaging systems, with only carbon disulphide and acetoin, both known volatiles of beef, detected in all three. This is the first study to investigate the effects of commercial packaging systems on VOC formation; it provides an understanding of the relationship of VOCs to the BBD that is essential for the development of on-pack freshness and quality sensors.

Multipole expansion of gravitational waves: from harmonic to Bondi coordinates

We transform the metric of an isolated matter source in the multipolar post-Minkowskian approximation from harmonic (de Donder) coordinates to radiative Newman-Unti (NU) coordinates. To linearized order, we obtain the NU metric as a functional of the mass and current multipole moments of the source, valid all-over the exterior region of the source. Imposing appropriate boundary conditions we recover the generalized Bondi-van der Burg-Metzner-Sachs residual symmetry group. To quadratic order, in the case of the mass-quadrupole interaction, we determine the contributions of gravitational-wave tails in the NU metric, and prove that the expansion of the metric in terms of the radius is regular to all orders. The mass and angular momentum aspects, as well as the Bondi shear, are read off from the metric. They are given by the radiative quadrupole moment including the tail terms.

THE CORRESPONDENCE OF THE EREZ-ROSEN SOLUTION WITH THE HARTLE-THORNE SOLUTION IN THE LIMITING CASE OF ~ࡽ AND ~ࡹ૛

The link between exterior solutions to the Einstein gravitational field equations such as the exact Erez-Rosen metric and approximate Hartle-Thorne metric is established here for the static case in the limit of linear mass quadrupole moment (Q) and second order terms in total mass (M). To this end, the Geroch-Hansen multipole moments are calculated for the Erez-Rosen and Hartle-Thorne solutions in order to find the relationship among the parameters of both metrics. The coordinate transformations are sought in a general form with two unknown functions in the corresponding limit of ~Q and ~M^2. By employing the perturbation theory, the approximate Erez-Rosen metric is written in the same coordinates as the Hartle-Thorne metric. By equating the radial and azimuthal components of the metric tensor of both solutions the sought functions are found in a straightforward way. It is shown that the approximation ~Q and ~M^2, which is used throughout the article, is physical and suitable for solving most problems of celestial mechanics in post-Newtonian physics. This approximation does not require the use of the Zipoy-Voorhees transformation, which is a necessary strict mathematical requirement in the ~Q approximation, i.e. when no other approximations are made. This implies that the explicit form of the coordinate transformations depends entirely on the approximation that is adopted in each particular case. The results obtained here are in agreement with the previous results in the literature and can be applied to different astrophysical goals. The paper pursues not only pure scientific, but also academic purposes and can be used as an auxiliary and additional material to the special courses of general theory of relativity, celestial mechanics and relativistic astrophysics.

Orbital spin dynamics of a millisecond pulsar around a massive BH with a general mass quadrupole

ABSTRACT We investigate the spin dynamics of a millisecond pulsar (MSP) in compact orbit around a Kerr-like massive BH with an general mass quadrupole. We use the Mathisson–Papetrou–Dixon formulation to compute the orbital and spin evolution of the MSP, accounting for the non-linear interaction of the pulsar’s energy–momentum tensor on the background space–time metric. We investigate how the MSP spin and BH quadrupole moment manifest in the pulsar spin-orbital dynamics. We discuss the astrophysical observational implications of these spin and orbital dynamics on the timing of a radio pulsar in an extreme mass ratio binary, e.g. a Galactic Centre pulsar. In particular, notable timing variations in the Einstein delay and Roemer delay are observed, along with modifications to the pulsar pulse profile.

The permanent ellipticity of the neutron star in PSR J1023+0038

ABSTRACT A millisecond pulsar having an ellipticity, which is an asymmetric mass distribution around its spin-axis, could emit continuous gravitational waves, which have not been detected so far. An indirect way to infer such waves is to estimate the contribution of the waves to the spin-down rate of the pulsar. The transitional pulsar PSR J1023+0038 is ideal and unique for this purpose because this is the only millisecond pulsar for which the spin-down rate has been measured in both accreting and non-accreting states. Here, we infer, from our formalism based on the complete torque budget equations and the pulsar magnetospheric origin of observed γ-rays in the two states, that PSR J1023+0038 should emit gravitational waves due to a permanent ellipticity of the pulsar. The formalism also explains some other main observational aspects of this source in a self-consistent way. As an example, our formalism naturally infers the accretion disc penetration into the pulsar magnetosphere, and explains the observed X-ray pulsations in the accreting state using the standard and well-accepted scenario. This, in turn, infers the larger pulsar spin-down power in the accreting state, which, in our formalism, explains the observed larger γ-ray emission in this state. Exploring wide ranges of parameter values of PSR J1023+0038, and not assuming an additional source of stellar ellipticity in the accreting state, we find the misaligned mass quadrupole moment of the pulsar in the range of (0.92–1.88) × 1036 g cm2, implying an ellipticity range of (0.48–0.93) × 10−9.

Rigid-body motion. Non-inertial coordinate systems

This chapter addresses the inertia tensor and its relation with the mass quadrupole moment tensor, the principal axes and the principal moments of inertia, evolution of the period of the Earth’s rotation around its axis due to the action of tidal forces, and the motion of the gyrocompass at a given latitude. The chapter also addresses precession of a symmetric top, the stability of rotations of an asymmetric top, “motion” of a plane disk which rolls in the field of gravity over a smooth horizontal plane, and the displacement from the vertical of a particle which is dropped from a given height with zero initial velocity. Finally, the chapter discusses the Lagrange point in the Sun-Jupiter system.

Rigid-body motion. Non-inertial coordinate systems

This chapter addresses the inertia tensor and its relation with the mass quadrupole moment tensor, the principal axes and the principal moments of inertia, evolution of the period of the Earth’s rotation around its axis due to the action of tidal forces, and the motion of the gyrocompass at a given latitude. The chapter also addresses precession of a symmetric top, the stability of rotations of an asymmetric top, “motion” of a plane disk which rolls in the field of gravity over a smooth horizontal plane, and the displacement from the vertical of a particle which is dropped from a given height with zero initial velocity. Finally, the chapter discusses the Lagrange point in the Sun-Jupiter system.

The structure and stability of extended, inclined circumplanetary disc or ring systems

ABSTRACT Large dips in the brightness for a number of stars have been observed, for which the tentative explanation is occultation of the star by a transiting circumplanetary disc or ring system. In order for the circumplanetary disc/rings to block the host star’s light, the disc must be tilted out of the planet’s orbital plane, which poses stability problems due to the radial extent of the disc required to explain the brightness dip durations. This work uses N-body integrations to study the structure and stability of circumplanetary disc/ring systems tilted out of the planet’s orbital plane by the spinning planet’s mass quadrupole. Simulating the disc as a collection of test particles with orbits initialized near the Laplace surface (equilibrium between tidal force from host star and force from planet’s mass quadrupole), we find that many extended, inclined circumplanetary discs remain stable over the duration of the integrations ($\sim 3\!-\!16 \, {\rm Myr}$). Two dynamical resonances/instabilities excite the particle eccentricities and inclinations: the Lidov-Kozai effect which occurs in the disc’s outer regions, and ivection resonance which occurs in the disc’s inner regions. Our work places constraints on the maximum radial extent of inclined circumplanetary disc/ring systems, and shows that gaps present in circumplanetary discs do not necessarily imply the presence of exomoons.