### Conveners

#### Sources of Gravitational Waves: Block 1

- Andrew Melatos (University of Melbourne)

#### Sources of Gravitational Waves: Block 2

- Liam Dunn (University of Melbourne)
- Andrew Melatos (University of Melbourne)

#### Sources of Gravitational Waves: Block 3

- Andrew Melatos ()

#### Sources of Gravitational Waves: Block 4

- Andrew Melatos (University of Melbourne)

### Description

The main aims of the session are: (1) to review recent progress in source modelling; (2) to discuss how GW detections can help solve problems in astrophysics and cosmology, e.g. binary star evolution; and (3) to explore ways in which GW signals can be combined with source models to answer fundamental questions in physics that cannot be probed easily in terrestrial laboratories, e.g. neutrino transport in ultradense environments, nuclear equation of state, origin of superstrong magnetic fields, et cetera.

Transient gravitational waves from catastrophic collisions of black holes and neutron stars have been observed by the Advanced LIGO and Virgo in the last few years. Studies are also carried out to look for something different -- the much fainter continuous gravitational radiation emitted by non-axisymmetric spinning neutron stars, or ultralight-boson condensates from spinning black holes. In...

Theories predict continuous gravitational waves may be emitted by rotating neutron stars. We present the results of three wide-band directed searches for continuous gravitational waves from young supernova remnants in the first half of the third Advanced LIGO and Virgo observing run. Using three complementary analysis pipelines, we search fifteen young supernova remnants between 10 Hz and 2...

After the groundbreaking gravitational wave detections of compact binary mergers, core-collapse supernova explosions of massive stars have come into focus as one of the next big challenges for gravitational wave astronomy. Thanks to increasingly mature simulations, our understanding of the expected time-frequency structure of the core-collapse supernova gravitational wave signal has advanced...

Core-collapse supernovae are fascinating astrophysical objects for multimessenger studies. Gravitational waves (GWs) are expected to play a role in the supernova explosion mechanism, but their modelling is also challenging due to the stochastic nature of the dynamics and the vast possible progenitors, and moreover, the GW detection from these objects is still elusive with the already advanced...

The detection of gravitational waves from core-collapse supernova explosions is a challenging task, yet to be achieved, in which it is key the connection between multiple messengers, including neutrinos and electromagnetic signals. We present a method for detecting these kind of signals based on machine learning techniques. We tested its robustness by injecting signals in the real noise data...

I will first define the stochastic gravitational-wave background (SGWB) and highlight the method we are using to detect it in the presence of correlated magnetic noise. I will then discuss astrophysical and cosmological sources and report on the current constraints imposed from a non-detection during the first three observing runs of the LIGO/Virgo/KAGRA collaboration. I will also address the...

Some particle physics models with an additional U(1) gauge interaction are interesting because those address the origin of neutrino masses. We show that, in a wide class of models, such an extra U(1) gauge symmetry breaking in the early universe can be first-order phase transition and hence generate a detectable amplitude of stochastic gravitational wave radiation in future experiments. We...

We present an overview of a search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1 (Sco X-1), using two pipelines: a hidden Markov model (HMM) and a cross correlation approach. This search improves on previous Sco X-1 searches by introducing new features for each pipeline. For the HMM model, we use a new frequency domain matched filter. The cross correlation...

Ground-based gravitational-wave detectors are becoming more sensitive, and in the near future we hope to detect a gravitational-wave background. However, as these detectors become more sensitive they will continue to run into new forms of noise. Correlated noise between spatially separated detectors will limit our intrinsic sensitivity, and have the potential to give a false detection. In this...

Gamma-ray bursts (GRBs) associated with gravitational wave events are, and will likely continue to be, viewed at a larger inclination than GRBs without gravitational wave detections. As demonstrated by the afterglow of GRB 170817A, this requires an extension of the common GRB afterglow models where it typically used to be sufficient to assume that the observer was looking straight into a jet...

The current Gravitational Wave (GW) surveys of Binary Black Hole (BBH) mergers provide unprecedented probes of the dynamics in extreme gravitational fields and relativistic velocities. It will be presented a new method to search for possible low energetic signal with unknown morphologies features in the post merger phase of the gravitational wave signal from a BBH coalescences. Such transient...

The isolated formation channel is one of the most studied formation

scenarios for stellar mass black hole binary (BBH) mergers detected by LIGO and Virgo. Focusing on the effects of

uncertain stellar and binary physics, we investigate this BBH formation channel using the rapid binary population

synthesis code SeBa.

Regardless of our assumptions, the two must common formation path...

Detections of neutron stars in binaries through gravitational waves offer a novel way to probe the properties of extremely dense matter. In this talk I will describe the properties of the signals we have observed, what they have already taught us, and what we expect to learn in the future. I will also discuss how information from gravitational waves can be combined and compared against other...

Over the past few years, we have enjoyed a wide variety of gravitational-wave detections of compact binary coalescences. However, the wait continues for the first observation of a rotating neutron star via gravitational waves and, so far, only upper limits on the size of the involved deformations have been obtained. For these reasons, the maximum quadrupole deformation (or mountain) that a...

The spectrum of ringdown waves which terminates the gravitational waveform of binary black hole merger contains information about both the properties of the merger’s remnant black hole, as well as the geometry of the system as it enters its final plunge and merger. This suggests that measurements of the ringdown spectrum could teach us about a binary’s geometry, provided we know how to invert...

Unlike gravitational waves from merging black holes and neutron stars that chirp significantly over the observational period of ground-based detectors, gravitational waves from binary white dwarfs are almost monochromatic. This makes it extremely challenging to measure their individual masses. Here, we take a novel approach of using finite-size effects and applying certain universal relations...

The recent analysis of gravitational wave data by the Ligo-Virgo collaboration (arXiv:2010.14533) provides evidence of merging binary black holes with non-zero spins.

Spinning binary BHs with aligned spins can result from the tidal spin-up of a Wolf-Rayet binary that survived the common envelope phase. However, tidal spin-up results in spins aligned with the orbital angular momentum, a...

The phenomenological waveform modelling program is one of the main approaches to accurately model gravitational wave signals from compact binary coalescences during all the emission stages, incorporating information from several analytical and numerical frameworks (Post-Newtonian theory, Numerical Relativity, Black-hole perturbation theory) in compact close-form computationally efficient...

As the gravitational-wave interferometers increase their sensitivity, they detect an ever larger number of compact binary coalescences: a small but significant fraction of which contains detectable higher multipoles in addition to the dominant (2, 2) mode. Such higher multipoles can be identified with a minimally-modeled extension of the coherent WaveBurst (cWB) burst pipeline.

During the...

The recent observing run of Advanced LIGO and Virgo was fruitful in gravitational-wave (GW) detections and the observation of GW190521 is one of the most important discoveries. With a remnant black hole of about 140 solar masses, this is the first strong evidence for the existence of intermediate-mass black holes that are heavier than stellar mass and lighter than supermassive black holes. In...

With the increasing sensitivities of the gravitational wave (GW) detectors and more detectors joining the international network, the chances of detection of a stochastic GW background (SGWB) is progressively increasing. Different astrophysical and cosmological processes are likely to give rise to backgrounds with distinct spectral signatures and distributions on the sky. The observed...

The low-mass X-ray binary Scorpius X-1 (Sco X-1) is a promising source of continuous gravitational waves for ground-based detectors. We use an improved method to search for signals with nearly constant frequency from Sco X-1 in the range of 40-180 Hz in LIGO O2 public data. Thanks to the efficiency of the search pipeline we can use a long coherence time and significantly improve the...

The elastic crust of a neutron star fractures repeatedly as it spins down electromagnetically. An idealized, macroscopic model of inhomogeneous crustal failure is presented based on a cellular automaton with nearest neighbor tectonic interactions involving strain redistribution and dissipation.

Predictions are made of the size and waiting-time distributions of failure events, as well as the...

In this report, we evaluate the performance of the proposed Euro-Asian network (EAN) of gravitational wave (GW) interferometers, which is planned taking into account the location of one of the detectors at the RAS Novosibirsk Scientific Center. EAN is formed by four detectors: VIRGO, KAGRA, LIGO India and Novosibirsk. The efficiency of this configuration is calculated based on typical...

The possibility to detect gravitational waves (GW) from planetary-mass primordial black hole (PBH) binaries with electromagnetic (EM) detectors of high-frequency GWs is investigated. We consider two patented experimental designs, based on the inverse Gertsenshtein effect, in which incoming GWs passing through a static magnetic field induce EM excitations inside either a TM cavity or a TEM...