Relativistic asteroseismology

2019 ◽  
pp. 443-478
Author(s):  
Nils Andersson
Keyword(s):  
General Relativity ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Oscillation Spectrum ◽  
New Family ◽  
Oscillation Modes ◽  
Stellar Oscillation ◽  
The Impact

The ideas behind gravitational-wave asteroseismology are introduced and motivated by a set of phenomenological relations. The impact of general relativity on different classes of stellar oscillation modes is outlined and the emergence of a new family of modes (the w-modes) associated with the dynamcis of spacetime itself is explained. The impact of relevant physics on a given neutron star’s oscillation spectrum is discussed. The instability of the f-mode in fast-spinning neutron stars is considered.

scholarly journals Gravitational Waves from Neutron Stars: A Review

2015 ◽  
Vol 32 ◽  
Author(s):  
Paul D. Lasky
Keyword(s):  
Neutron Stars ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Gravitational Radiation ◽  
Superfluid Turbulence ◽  
Physical Processes ◽  
Gravitational Wave Detection ◽  
Wave Detection ◽  
Oscillation Modes ◽  
Stellar Oscillation

AbstractNeutron stars are excellent emitters of gravitational waves. Squeezing matter beyond nuclear densities invites exotic physical processes, many of which violently transfer large amounts of mass at relativistic velocities, disrupting spacetime and generating copious quantities of gravitational radiation. I review mechanisms for generating gravitational waves with neutron stars. This includes gravitational waves from radio and millisecond pulsars, magnetars, accreting systems, and newly born neutron stars, with mechanisms including magnetic and thermoelastic deformations, various stellar oscillation modes, and core superfluid turbulence. I also focus on what physics can be learnt from a gravitational wave detection, and where additional research is required to fully understand the dominant physical processes at play.

The stellar graveyard

2019 ◽  
pp. 177-206
Author(s):  
Nils Andersson
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Stellar Evolution ◽  
White Dwarfs ◽  
Supermassive Black Holes ◽  
Compact Objects ◽  
Fermi Gases ◽  
The 1950S

This chapter introduces the different classes of compact objects—white dwarfs, neutron stars, and black holes—that are relevant for gravitational-wave astronomy. The ideas are placed in the context of developing an understanding of the likely endpoint(s) of stellar evolution. Key ideas like Fermi gases and the Chandrasekhar mass are discussed, as is the emergence of general relativity as a cornerstone of astrophysics in the 1950s. Issues associated with different formation channels for, in particular, black holes are considered. The chapter ends with a discussion of the supermassive black holes that are found at the centre of galaxies.

Dynamical versus isolated formation channels of gravitational wave sources

2018 ◽  
Vol 14 (S346) ◽  
pp. 397-416
Author(s):  
Michela Mapelli
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Theoretical Models ◽  
Stellar Winds ◽  
Core Collapse ◽  
Dynamical Processes ◽  
New Approach ◽  
The Impact

AbstractWhat are the formation channels of merging black holes and neutron stars? The first two observing runs of Advanced LIGO and Virgo give us invaluable insights to address this question, but a new approach to theoretical models is required, in order to match the challenges posed by the new data. In this review, I discuss the impact of stellar winds, core-collapse and pair instability supernovae on the formation of compact remnants in both isolated and dynamically formed binaries. Finally, I show that dynamical processes, such as the runaway collision scenario and the Kozai-Lidov mechanism, leave a clear imprint on the demography of merging systems.

General relativity and neutron stars

2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641017
Author(s):  
D. G. Yakovlev
Keyword(s):  
General Relativity ◽  
Neutron Star ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Mass Measurements ◽  
Einstein Theory ◽  
Superdense Matter ◽  
Compact Binaries ◽  
Star Models ◽  
Neutron Star Mass

General Relativity affects all major aspects of neutron star structure and evolution including radiation from the surface, neutron star models, evolution in compact binaries. It is widely used for neutron star mass measurements and for studying properties of superdense matter in neutron stars. Observations of neutron stars help testing General Relativity and planning gravitational wave experiments. No deviations from Einstein Theory of Gravity have been detected so far from observations of neutron stars.

The Discovery of Gravitational Wave Emission

2018 ◽  
pp. 103-105
Author(s):  
Alvaro De Rújula
Keyword(s):  
General Relativity ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Binary Stars ◽  
Binary Pulsar ◽  
Wave Emission

Neutron stars, binary stars and pulsars. The Arecibo radio antenna. The discovery of the first binary pulsar (PS1913+16) by Husle and Taylor. This pulsar’s understanding in general relativity: A fantastic success.

scholarly journals Gravitational-Wave Asteroseismology as a Tool to Reveal the Equation of State of Relativistic Neutron Stars

2002 ◽  
Vol 185 ◽  
pp. 612-615
Author(s):  
Johannes Ruoff
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Oscillation Modes

AbstractThe equation of state (EOS) is still the big unknown in the physics of neutron stars. An accurate measurement of both the mass and the radius of a neutron star would put severe constraints on the range of possible EOSs. I discuss how the parameters of the oscillation modes of a neutron star, measured from the emitted gravitational waves, can in principle be used to infer its mass and radius, and thus reveal its EOS.

scholarly journals Gravitational wave content and stability of uniformly, rotating, triaxial neutron stars in general relativity

2017 ◽  
Vol 95 (12) ◽  
Author(s):  
Antonios Tsokaros ◽  
Milton Ruiz ◽  
Vasileios Paschalidis ◽  
Stuart L. Shapiro ◽  
Luca Baiotti ◽  
...  
Keyword(s):  
General Relativity ◽  
Neutron Stars ◽  
Gravitational Wave

scholarly journals Post-Newtonian gravitational and scalar waves in scalar-Gauss-Bonnet gravity

2021 ◽  
Author(s):  
Banafsheh Shiralilou ◽  
Tanja Hinderer ◽  
Samaya Nissanke ◽  
Nestor Ortiz ◽  
Helvi Witek
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Gravitational Wave ◽  
Strong Field ◽  
Field Tests ◽  
Theoretical Modelling ◽  
Bonnet Gravity ◽  
Weak Coupling Approximation ◽  
Tests Of Gravity ◽  
The Impact

Abstract Gravitational waves emitted by black hole binary inspiral and mergers enable unprecedented strong-field tests of gravity, requiring accurate theoretical modelling of the expected signals in extensions of General Relativity. In this paper we model the gravitational wave emission of inspiralling binaries in scalar Gauss-Bonnet gravity theories. Going beyond the weak-coupling approximation, we derive the gravitational waveform to relative first post-Newtonian order beyond the quadrupole approximation and calculate new contributions from nonlinear curvature terms. We also compute the scalar waveform to relative 0.5PN order beyond the leading -0.5PN order terms. We quantify the effect of these terms and provide ready-to-implement gravitational wave and scalar waveforms as well as the Fourier domain phase for quasi-circular binaries. We also perform a parameter space study, which indicates that the values of black hole scalar charges play a crucial role in the detectability of deviation from General Relativity. We also compare the scalar waveforms to numerical relativity simulations to assess the impact of the relativistic corrections to the scalar radiation. Our results provide important foundations for future precision tests of gravity.

scholarly journals Inferring the dense nuclear matter equation of state with neutron star tides

2022 ◽  
Vol 258 ◽  
pp. 07002
Author(s):  
Pantelis Pnigouras ◽  
Nils Andersson ◽  
Andrea Passamonti
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Direct Detection ◽  
Oscillation Mode ◽  
Finite Size ◽  
Dense Nuclear Matter ◽  
Oscillation Modes ◽  
Stellar Oscillation ◽  
Star Binary ◽  
The Impact

During the late stages of a neutron star binary inspiral finite-size effects come into play, with the tidal deformability of the supranuclear density matter leaving an imprint on the gravitational-wave signal. As demonstrated in the case of GW170817—the first direct detection of gravitational waves from a neutron star binary—this can lead to strong constraints on the neutron star equation of state. As detectors become more sensitive, effects which may have a smaller influence on the neutron star tidal deformability need to be taken into consideration. Dynamical effects, such as oscillation mode resonances triggered by the orbital motion, have been shown to contribute to the tidal deformability, especially close to the neutron star coalesence, where current detectors are most sensitive. We calculate the contribution of the various stellar oscillation modes to the tidal deformability and demonstrate the (anticipated) dominance of the fundamental mode. We show what the impact of the matter composition is on the tidal deformability, as well as the changes induced by more realistic additions to the problem, e.g. the presence of an elastic crust. Finally, based on this formulation, we develop a simple phenomenological model describing the effective tidal deformability of neutron stars and show that it provides a surprisingly accurate representation of the dynamical tide close to merger.

scholarly journals Pulsar Identification of Background Spectra of LIGO Data

2018 ◽  
Vol 1 (2) ◽  
Keyword(s):  
Black Holes ◽  
Exact Solution ◽  
General Relativity ◽  
Time Delay ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Compact Objects ◽  
Gravitational Redshift ◽  
Wave Spectra

By choosing the metric (called physical metric) in general relativity as the exact solution to the Einstein equation that fits the time delay data, one can determine the size and gravitational redshift on the surface of compact objects (neutron stars and black holes). The author shows that the physical metric is invariant by rotation. As a result, the frequencies of gravitational waves from pulsars are represented as n * f / for pulsar frequency f and harmonics n. Based on this result, the author has identified potential pulsar candidates with gravitational wave spectra. This result will be critical in the study of gravitational redshift of compact objects.

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