Detecting **Gravitational** **Waves** in Data with Non-Gaussian Noise

**gravitational**

**waves**crucially depend on exact signal processing of noisy strain data from

**gravitational**

**wave**detectors, which are known to exhibit significant non-Gaussian behavior. In this paper, we study two distinct non-Gaussian effects in the LIGO/Virgo data which reduce the sensitivity of searches: first, variations in the noise power spectral density (PSD) on timescales of more than a few seconds; and second, loud and abrupt transient `glitches' of terrestrial or instrumental origin. We derive a simple procedure to correct, at first order, the effect of the variation in the PSD on the search background. Given the knowledge of the existence of localized glitches in particular segments of data, we also develop a method to insulate statistical inference from these glitches, so as to cleanly excise them without affecting the search background in neighboring seconds. We show the importance of applying these methods on the publicly available LIGO data, and measure an increase in the detection volume of at least $15\%$ from the PSD-drift correction alone, due to the improved background distribution.

10/10 relevant

arXiv

Signatures of noncommutativity in bar detectors of **gravitational** **waves**

**gravitational**

**wave**perturbation ($h$) in the Hamiltonian. Interestingly, the second order term in $h$ shows a transition between the ground state and one of the perturbed second excited states that was absent when the calculation was restricted only to first order in $h$.

9/10 relevant

arXiv

Detectability of Intermediate-Mass Black Holes in Multiband
**Gravitational** **Wave** Astronomy

**gravitational**

**waves**is a powerful tool for surveying the population of black holes across the universe. The first

**gravitational**

**wave**catalog from LIGO has detected black holes as heavy as $\sim50~M_\odot$, colliding when our Universe was about half its current age. However, there is yet no unambiguous evidence of black holes in the intermediate-mass range of $10^{2-5}~M_\odot$. Recent electromagnetic observations have hinted at the existence of IMBHs in the local universe; however, their masses are poorly constrained. The likely formation mechanisms of IMBHs are also not understood. Here we make the case that multiband

**gravitational**

**wave**astronomy --specifically, joint observations by space- and ground-based

**gravitational**

**wave**detectors-- will be able to survey a broad population of IMBHs at cosmological distances. By utilizing general relativistic simulations of merging black holes and state-of-the-art

**gravitational**waveform models, we classify three distinct population of binaries with IMBHs in the multiband era and discuss what can be observed about each. Our studies show that multiband observations involving the upgraded LIGO detector and the proposed space-mission LISA would detect the inspiral, merger and ringdown of IMBH binaries out to redshift ~2. Assuming that next-generation detectors, Einstein Telescope, and Cosmic Explorer, are operational during LISA's mission lifetime, we should have multiband detections of IMBH binaries out to redshift ~5. To facilitate studies on multiband IMBH sources, here we investigate the multiband detectability of IMBH binaries. We provide analytic relations for the maximum redshift of multiband detectability, as a function of black hole mass, for various detector combinations. Our study paves the way for future work on what can be learned from IMBH observations in the era of multiband

**gravitational**

**wave**astronomy.

10/10 relevant

arXiv

Multi-messenger **Gravitational**-**Wave** + High-Energy Neutrino Searches with
LIGO, Virgo, and IceCube

**gravitational**

**waves**and high-energy neutrinos provide important insights into the dynamics of and particle acceleration by black holes and neutron stars. Expand abstract.

**gravitational**

**waves**and high-energy neutrinos provide important insights into the dynamics of and particle acceleration by black holes and neutron stars. With LIGO's third observing period (O3), the number of

**gravitational**

**wave**detections has been substantially increased. The rapid identification of joint signals is crucial for electromagnetic follow-up observations of transient emission that is only detectable for short periods of time. High-energy neutrino direction can be reconstructed to sub-degree precision, making a joint detection far better localized than a standalone

**gravitational**-

**wave**signal. We present the latest sensitivity of joint searches and discuss the Low-Latency Algorithm for Multi-messenger Astrophysics (LLAMA) that combines LIGO/Virgo

**gravitational**-

**wave**candidates and searches in low-latency for coincident high-energy neutrinos from the IceCube Neutrino Observatory. We will further discuss future prospects of joint searches from the perspective of better understanding the interaction of relativistic and sub-relativistic outflows from binary neutron star mergers.

10/10 relevant

arXiv

Asymmetric accretion and thermal `mountains' in magnetized neutron star crusts

**gravitational**

**wave**signals from systems with higher... Expand abstract.

**gravitational**

**wave**searches, as asymmetric accretion may lead to quadrupolar deformations, or `mountains', on the crust of the star, which source

**gravitational**

**wave**emission at twice the rotation frequency. The

**gravitational**

**wave**torque may also impact on the spin evolution of the star, possibly dictating the currently observed spin periods of neutron stars in Low Mass X-ray Binaries and leading to the increased spindown rate observed during accretion in PSR J1023+0038. Previous studies have shown that deformed reaction layers in the crust of the neutron star lead to thermal and compositional gradients that can lead to

**gravitational**

**wave**emission. However, there are no realistic constraints on the level of asymmetry that is expected. In this paper we consider a natural source of asymmetry, namely the magnetic field, and calculate the density and pressure perturbations that are expected in the crust of accreting neutron stars. In general we find that only the outermost reaction layers of the neutron star are strongly perturbed. The mass quadrupole that we estimate is generally small and cannot explain the increase of spin-down rate of PSR J1023+0038. However, if strong shallow heating sources are present at low densities in the crust, as cooling observations suggest, these layers will be strongly perturbed and the resulting quadrupole could explain the observed spindown of PSR J1023+0038, and lead to observable

**gravitational**

**wave**signals from systems with higher accretion rates.

4/10 relevant

arXiv

Accretion-Induced Collapse of Dark Matter Admixed White Dwarfs -- II:
Rotation and **Gravitational**-**wave** Signals

**gravitational**-

**wave**(GW) signals. For initial WD models with the same central baryon density, the admixed DM is found to delay the plunge and bounce phases of AIC, and decrease the central density and mass of the proto-neutron star (PNS) produced. The bounce time, central density and PNS mass generally depend on two parameters, the admixed DM mass $M_\mathrm{DM}$ and the ratio between the rotational kinetic and

**gravitational**energies of the inner core at bounce $\beta_\mathrm{ic,b}$. The emitted GWs have generic waveform shapes and the variation of their amplitudes $h_+$ show a degeneracy on $\beta_\mathrm{ic,b}$ and $M_\mathrm{DM}$. We found that the ratios between the GW amplitude peaks around bounce allow breaking the degeneracy and extraction of both $\beta_\mathrm{ic,b}$ and $M_\mathrm{DM}$. Even within the uncertainties of nuclear matter equation of state, a DM core can be inferred if its mass is greater than 0.03 $M_{\odot}$. We also discuss possible DM effects on the GW signals emitted by PNS g-mode oscillations. GW may boost the possibility for the detection of AIC, as well as open a new window in the indirect detection of DM.

7/10 relevant

arXiv

Helical phase inflation and its observational constraints

**gravitational**

**waves**will be within the reach of the future LiteBIRD satellite experiment.

4/10 relevant

arXiv

**Gravitational** **wave** detection beyond the standard quantum limit using a
negative-mass spin system and virtual rigidity

**Gravitational**

**wave**detectors (GWDs), which have brought about a new era in astronomy, have reached such a level of maturity that further improvement necessitates quantum-noise-evading techniques. Expand abstract.

**Gravitational**

**wave**detectors (GWDs), which have brought about a new era in astronomy, have reached such a level of maturity that further improvement necessitates quantum-noise-evading techniques. Numerous proposals to this end have been discussed in the literature, e.g., invoking frequency-dependent squeezing or replacing the current Michelson interferometer topology by that of the quantum speedmeter. Recently, a proposal based on the linking of a standard interferometer to a negative-mass spin system via entangled light has offered an unintrusive and small-scale new approach to quantum noise evasion in GWDs [F.Y. Khalili and E.S. Polzik, Phys. Rev. Lett. 121, 031101 (2018)]. The solution proposed therein does not require modifications to the highly refined core optics of the present GWD design and, when compared to previous proposals, is less prone to losses and imperfections of the interferometer. In the present article we refine this scheme to an extent that the requirements on the auxiliary spin system are feasible with state-of-the-art implementations. This is accomplished by matching the effective (rather than intrinsic) susceptibilities of the interferometer and spin system using the virtual rigidity concept, which, in terms of implementation, requires only suitable choices of the various homodyne, probe, and squeezing phases.

7/10 relevant

arXiv

An Optically Targeted Search for **Gravitational** **Waves** emitted by
Core-Collapse Supernovae during the First and Second Observing Runs of
Advanced LIGO and Advanced Virgo

**gravitational**-

**wave**transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant

**gravitational**-

**wave**candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. For neutrino-driven explosions the distance at which we reach 50% detection efficiency is approaching 5 kpc, and for magnetorotationally-driven explosions is up to 54 kpc. However, waveforms for extreme emission models are detectable up to 28 Mpc. For the first time, the

**gravitational**-

**wave**data enabled us to exclude part of the parameter spaces of two extreme emission models with confidence up to 83%, limited by coincident data coverage. Besides, using ad hoc harmonic signals windowed with Gaussian envelopes we constrained the

**gravitational**-

**wave**energy emitted during core-collapse at the levels of $4.27\times 10^{-4}\,M_\odot c^2$ and $1.28\times 10^{-1}\,M_\odot c^2$ for emissions at 235 Hz and 1304 Hz respectively. These constraints are two orders of magnitude more stringent than previously derived in the corresponding analysis using initial LIGO, initial Virgo and GEO 600 data.

10/10 relevant

arXiv

**Gravitational** **wave** emission from unstable accretion discs in tidal
disruption events

**Gravitational**

**waves**can be emitted by accretion discs if they undergo instabilities that generate a time varying mass quadrupole. In this work we investigate the

**gravitational**signal generated by a thick accretion disc of $1 M_{\odot}$ around a static super-massive black hole of $10^{6}M_{\odot}$, assumed to be formed after the tidal disruption of a solar type star. This torus has been shown to be unstable to a global non-axisymmetric hydrodynamic instability, the Papaloizou-Pringle instability, in the case where it is not already accreting and has a weak magnetic field. We start by deriving analytical estimates of the maximum amplitude of the

**gravitational**

**wave**signal, with the aim to establish its detectability by the Laser Interferometer Space Antenna (LISA). Then, we compare these estimates with those obtained through a numerical simulation of the torus, made with a 3D smoothed particle hydrodynamics code. Our numerical analysis shows that the measured strain is two orders of magnitude lower than the maximum value obtained analytically. However, accretion discs affected by the Papaloizou-Pringle instability may still be interesting sources for LISA, if we consider discs generated after deeply penetrating tidal disruptions of main sequence stars of higher mass.

10/10 relevant

arXiv