Core-Collapse Supernova Physics in the Multi-Messenger Era

Eighty-five years following the historic proposal that core-collapse supernovae accompanied the transition of evolved massive stars to neutron stars [1], the mechanism through which these collapsing stars explode remains uncertain. While supernovae are observed on a daily basis across the electromagnetic spectrum, neutrinos and gravitational waves, emitted from the very heart of the core-collapse supernova central engine, provide a direct glimpse of the dynamics driving the explosion. The joint gravitational wave and electromagnetic observations of a colliding neutron star binary system on 17th August 2017 heralded a new era for multi-messenger astronomy [2]. The next galactic core-collapse supernova presents an unparalleled opportunity to directly probe core-collapse supernova physics and the explosion mechanism. This thesis explores a number of topics in multi-messenger astronomy and core-collapse supernova physics. First, it tackles the observation problem; detailing an astrophysically motivated search protocol for gravitational waves from core-collapse supernovae triggered by observations of neutrino and/or electromagnetic counterparts. Applying these methods to a number of hypothetical observational scenarios, it presents sensitivity estimates for the second generation of gravitational wave interferometric detectors to both realistic and speculative emission mechanisms associated with core-collapse supernovae. Next, it addresses the prospects for post-detection inference; developing a Bayesian toolkit to interpret gravitational wave observations from core-collapse supernovae and augment current understanding of the explosion mechanism. A proof-of-principle study is also presented, using tailor-made simulations to demonstrate the viability of extracting the angular momentum distribution of nascent millisecond proto-neutron stars from their gravitational wave echoes. Thereafter, it considers the ramifications of failure to accurately capture proto-neutron star hydrodynamics in core-collapse supernova simulations; exploring the influence on the explosion mechanism of gravito-acoustic waves generated by convection in the proto-neutron star mantle. Finally, it ponders the impact of advances in multi-messenger astronomy and source modelling over the next twenty years on the understanding of core-collapse supernova physics.</p

Open data from the first and second observing runs of Advanced LIGO and Advanced Virgo

Advanced LIGO and Advanced Virgo are monitoring the sky and collecting gravitational-wave strain data with sufficient sensitivity to detect signals routinely. In this paper we describe the data recorded by these instruments during their first and second observing runs. The main data products are gravitational-wave strain time series sampled at 16384 Hz. The datasets that include this strain measurement can be freely accessed through the Gravitational Wave Open Science Center at http://gw-openscience.org, together with data-quality information essential for the analysis of LIGO and Virgo data, documentation, tutorials, and supporting software

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

International audienceSpinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far