scholarly journals Spin effects on neutron star fundamental-mode dynamical tides: Phenomenology and comparison to numerical simulations

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Jan Steinhoff ◽  
Tanja Hinderer ◽  
Tim Dietrich ◽  
Francois Foucart
Keyword(s):  
Neutron Star ◽  
Numerical Simulations ◽  
Fundamental Mode ◽  
Spin Effects

scholarly journals A Gravitational-Wave Perspective on Neutron-Star Seismology

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 97
Author(s):  
Nils Andersson
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Fundamental Mode ◽  
Compact Binaries

We provide a bird’s-eye view of neutron-star seismology, which aims to probe the extreme physics associated with these objects, in the context of gravitational-wave astronomy. Focussing on the fundamental mode of oscillation, which is an efficient gravitational-wave emitter, we consider the seismology aspects of a number of astrophysically relevant scenarios, ranging from transients (like pulsar glitches and magnetar flares), to the dynamics of tides in inspiralling compact binaries and the eventual merged object and instabilities acting in isolated, rapidly rotating, neutron stars. The aim is not to provide a thorough review, but rather to introduce (some of) the key ideas and highlight issues that need further attention.

scholarly journals Jet Propagation in Neutron Star Mergers and GW170817

2019 ◽  
Author(s):  
Hamid Hamidani ◽  
Kenta Kiuchi ◽  
Kunihito Ioka
Keyword(s):  
Neutron Star ◽  
Numerical Simulations ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Expansion Velocity ◽  
Analytic Model ◽  
Binary Neutron Star ◽  
Central Engine ◽  
Relativistic Jet ◽  
Wave Event

Abstract The gravitational wave event from the binary neutron star (BNS) merger GW170817 and the following multi-messenger observations present strong evidence for i) merger ejecta expanding with substantial velocities and ii) a relativistic jet which had to propagate through the merger ejecta. The ejecta’s expansion velocity is not negligible for the jet head motion, which is a fundamental difference from the other systems like collapsars and active galactic nuclei. Here we present an analytic model of the jet propagation in an expanding medium. In particular, we notice a new term in the expression of the breakout time and velocity. In parallel, we perform a series of over a hundred 2D numerical simulations of jet propagation. The BNS merger ejecta is prepared based on numerical relativity simulations of a BNS merger with the highest-resolution to date. We show that our analytic results agree with numerical simulations over a wide parameter space. Then we apply our analytic model to GW170817, and obtain two solid constraints on: i) the central engine luminosity as Liso, 0 ∼ 3 × 1049 − 2.5 × 1052 erg s−1, and on ii) the delay time between the merger and engine activation t0 − tm < 1.3 s. The engine power implies that the apparently-faint short gamma-ray burst (sGRB) sGRB 170817A is similar to typical sGRBs if observed on-axis.

scholarly journals Detectability of neutron star merger afterglows

2019 ◽  
Vol 488 (2) ◽  
pp. 2405-2411 ◽  
Author(s):  
Ore Gottlieb ◽  
Ehud Nakar ◽  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Numerical Simulations ◽  
Peak Time ◽  
Low Density ◽  
Viewing Angle ◽  
Estimated Parameters ◽  
Analytic Expressions

ABSTRACT VLBI and JVLA observations revealed that GW170817 involved a narrow jet (θj ≈ 4°) that dominated the afterglow peak at our viewing angle, θobs ≈ 20°. This implies that at the time of the afterglow peak, the observed signal behaved like an afterglow of a top-hat jet seen at θobs ≫ θj, and it can be modelled by analytic expressions that describe such jets. We use a set of numerical simulations to calibrate these analytic relations and obtain generic equations for the peak time and flux of such an afterglow as seen from various observing angles. Using the calibrated equations and the estimated parameters of GW170817, we estimate the detectability of afterglows from future double neutron star mergers during the Advanced LIGO/Virgo observation run O3. GW170817 took place at a relatively low-density environment. Afterglows of similar events will be detectable only at small viewing angles, θobs ≲ 20°, and only 20 per cent of the GW detections of these events will be accompanied by a detectable afterglow. At higher densities, more typical to sGRB sites, up to $70\,\rm{per\,cent}$ of the GW detections are expected to be followed by a detectable afterglow, typically at θobs ∼ 30°. We also provide the latest time one should expect an afterglow detection. We find that for typical parameters, if the jet emission had not been detected within about a year after the merger, it is unlikely to be ever detected.

scholarly journals Numerical simulations of neutron star-black hole binaries in the near-equal-mass regime

2019 ◽  
Vol 99 (10) ◽  
Author(s):  
F. Foucart ◽  
M. D. Duez ◽  
L. E. Kidder ◽  
S. M. Nissanke ◽  
H. P. Pfeiffer ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Numerical Simulations ◽  
Equal Mass ◽  
Black Hole Binaries

scholarly journals Nonlinear-in-spin effects in effective-one-body waveform models of spin-aligned, inspiralling, neutron star binaries

2019 ◽  
Vol 99 (4) ◽  
Author(s):  
Alessandro Nagar ◽  
Francesco Messina ◽  
Piero Rettegno ◽  
Donato Bini ◽  
Thibault Damour ◽  
...  
Keyword(s):  
Neutron Star ◽  
Spin Effects

scholarly journals Gravitational wave signatures of dark matter cores in binary neutron star mergers by using numerical simulations

2019 ◽  
Vol 100 (4) ◽  
Author(s):  
Miguel Bezares ◽  
Daniele Viganò ◽  
Carlos Palenzuela
Keyword(s):  
Dark Matter ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Numerical Simulations ◽  
Binary Neutron Star

SOME CONSTRAINTS ON TORSION DETECTION PHYSICS

1993 ◽  
Vol 08 (28) ◽  
pp. 5095-5100 ◽  
Author(s):  
C.M. ZHANG
Keyword(s):  
Neutron Star ◽  
Spin Rotation ◽  
Spin Effects ◽  
Dirac Particles ◽  
Rotating Body ◽  
Magnetic Spin

Two kinds of sources of torsion, aligned spin and macroscopic rotation, are demonstrated by analyzing the Lagrangian. In the case of Dirac particles as a direct sensor for torsion, the torsion spin effects are strongly influenced by the backgrounds, which are magnetic spin, rotation spin and gravity spin. Increasing the source of the torsion is equivalent to increasing the background itself. The first proposed criterion for torsion detection is that any astrophysics experiments have no hope of showing the evidence for torsion directly. The promised evidence for torsion must be cumulative and indirect on the neutron star. The macroscopic rotating body, an indirect sensor for torsion, has not been able to present the trace of the torsion in the experiments carried out so far.

scholarly journals The phenomenology of dynamical neutron star tides

2021 ◽  
Vol 503 (1) ◽  
pp. 533-539 ◽  
Author(s):  
N Andersson ◽  
P Pnigouras
Keyword(s):  
Data Analysis ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Frequency Dependence ◽  
Parameter Space ◽  
Fundamental Mode ◽  
Attractive Alternative ◽  
Relevant Parameter ◽  
Accurate Representation ◽  
Late Stages

ABSTRACT We introduce a phenomenological, physically motivated, model for the effective tidal deformability of a neutron star, adding the frequency dependence (associated with the star’s fundamental mode of oscillation) that comes into play during the late stages of the binary inspiral. Testing the model against alternative descriptions, we demonstrate that it provides an accurate representation of the dynamical tide up to close to merger. The simplicity of the prescription makes it an attractive alternative for a gravitational-wave data analysis implementation, facilitating an inexpensive construction of a large number of templates covering the relevant parameter space.

scholarly journals A WHITE DWARF-NEUTRON STAR RELATIVISTIC BINARY MODEL FOR SOFT GAMMA-RAY REPEATERS

2005 ◽  
Vol 14 (09) ◽  
pp. 1473-1484 ◽  
Author(s):  
HERMAN J. MOSQUERA CUESTA
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Orbital Period ◽  
White Dwarf ◽  
Fundamental Mode ◽  
Gamma Ray ◽  
High Mass ◽  
Integer Number ◽  
Binary Separation ◽  
Massive Neutron Star

A scenario for soft gamma-ray repeaters (SGRs) is introduced in which gravitational radiation reaction (GRR) effects drive the dynamics of an ultrashort orbital period X-ray binary embracing a high-mass donor white dwarf (WD) to a rapidly rotating low magnetized massive neutron star (NS) surrounded by a thick, dense and massive accretion torus. Driven by GRR, over timescales of ΔTrep~ 10 years, the binary separation reduces, the WD overflows its Roche lobe and the mass transfer drives unstable the accretion disk around the NS. As the binary circular orbital period is a multiple integer number (m) of the period of the WD fundamental mode,37the WD is since long pulsating at its fundamental mode; and most of its harmonics, due to the tidal interaction with its NS orbital companion. Hence, when the powerful irradiation glows onto the WD; from the fireball ejected as part of the disk matter slumps onto the NS, it is partially absorbed. This huge energy excites other WD radial (p-mode) pulsations.34,35After each mass-transfer episode the binary separation (and orbital period) is augmented significantly1,5due to the binary's angular momentum redistribution. Thus a new adiabatic inspiral phase driven by GRR reaction starts which brings the binary close again, and the process repeats after a time span ΔTrep. This model allows to explain most of SGRs observational features: their recurrent activity, energetics of giant superoutbursts and quiescent stages, and particularly the intriguing subpulses discovered by BeppoSAX,10which are suggested here to be overtones of the WD radial fundamental mode (see the accompanying paper).31

scholarly journals Binary Neutron Star and Short Gamma-Ray Burst Simulations in Light of GW170817

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 119 ◽  
Author(s):  
Antonios Nathanail
Keyword(s):  
Neutron Star ◽  
Gravitational Wave ◽  
Electromagnetic Radiation ◽  
Numerical Simulations ◽  
Gravitational Waves ◽  
Gamma Ray ◽  
Numerical Relativity ◽  
Gamma Ray Burst ◽  
Binary Neutron Star ◽  
The Status

In the dawn of the multi-messenger era of gravitational wave astronomy, which was marked by the first ever coincident detection of gravitational waves and electromagnetic radiation, it is important to take a step back and consider our current established knowledge. Numerical simulations of binary neutron star mergers and simulations of short GRB jets must combine efforts to understand such complicated and phenomenologically rich explosions. We review the status of numerical relativity simulations with respect to any jet or magnetized outflow produced after merger. We compare what is known from such simulations with what is used and obtained from short GRB jet simulations propagating through the BNS ejecta. We then review the established facts on this topic, as well as discuss things that need to be revised and further clarified.

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