E. J. Howell
A5048798160- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Geophysics and Sensor Technology
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Seismic Waves and Analysis
- Radio Astronomy Observations and Technology
- Advanced Frequency and Time Standards
- Atomic and Subatomic Physics Research
- Statistical and numerical algorithms
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Seismology and Earthquake Studies
- Adaptive optics and wavefront sensing
- Stellar, planetary, and galactic studies
- Cold Atom Physics and Bose-Einstein Condensates
- Black Holes and Theoretical Physics
- GNSS positioning and interference
- Magnetic confinement fusion research
- Dark Matter and Cosmic Phenomena
- Solar and Space Plasma Dynamics
ARC Centre of Excellence for Gravitational Wave Discovery
2017-2025
The University of Western Australia
2016-2025
SpaceX (United States)
2022
Goddard Space Flight Center
2022
Monash University
2019
University of Amsterdam
2019
Netherlands Institute for Radio Astronomy
2019
Cardiff University
2011
Carleton College
2011
California Institute of Technology
2011
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in new era multi-messenger astronomy. In this paper, we present event GW170817 and its SSS17a/DLT17ck (IAU label AT2017gfo) 14 Australian telescopes partner observatories as part Australian-based Australian-led research programs. We report early- late-time multi-wavelength observations, including optical imaging spectroscopy,...
We report the discovery of four Fast Radio Bursts (FRBs) in ongoing SUrvey for Pulsars and Extragalactic at Parkes Telescope: FRBs 150610, 151206, 151230 160102. Our real-time discoveries have enabled us to conduct extensive, rapid multimessenger follow-up 12 major facilities sensitive radio, optical, X-ray, gamma-ray photons neutrinos on time-scales ranging from an hour a few months post-burst. No counterparts were found we provide upper limits afterglow luminosities. None seen repeat....
We present optical, X-ray and gamma-ray observations of GRB 111209A, observed at a redshift z = 0.677. show that this event was active in its prompt phase for about 25000 s, making it the longest burst ever observed. This rare could have been detected up to ∼ 1.4 gamma-rays. Compared other long bursts (GRBs), 111209A is clear outlier energy-fluence duration plane. The high-energy emission shows no sign strong blackbody component, signature tidal disruption event, or supernova shock breakout....
The favoured progenitor model for short $\gamma$-ray bursts (SGRBs) is the merger of two neutron stars that triggers an explosion with a burst collimated $\gamma$-rays. Following initial prompt emission, some SGRBs exhibit plateau phase in their $X$-ray light curves indicates additional energy injection from central engine, believed to be rapidly rotating, highly magnetised star. collapse this `protomagnetar' black hole likely responsible steep decay flux observed at end plateau. In letter,...
Short gamma-ray bursts (SGRBs) observed by Swift potentially reveal the first insight into cataclysmic compact object mergers. To ultimately acquire a fundamental understanding of these events requires pan-spectral observations and knowledge their spatial distribution to differentiate between proposed progenitor populations. Up 2012 April, there are only some 30 per cent SGRBs with reasonably firm redshifts, this sample is highly biased limited sensitivity detect SGRBs. We account for...
This paper reports a comprehensive study on the gravitational wave (GW) background from compact binary coalescences. We consider in our calculations newly available observation-based neutron star and black hole mass distributions complete analytical waveforms that include post-Newtonian amplitude corrections. Our results show that: (i) effects cause small reduction GW signal; (ii) below 100 Hz depends primarily local coalescence rate $r_0$ average chirp is independent of distribution; (iii)...
Gravitational-wave (GW) detectors can contribute to the measurement of cosmological parameters and testing dark-energy sector alternatives $\Lambda$CDM, by using standard sirens. In this paper we focus on binary neutron stars with a counterpart detected through gamma-ray burst (GRB), both at second-generation network made advanced LIGO+advanced Virgo+LIGO India+Kagra, third-generation (3G) detectors, discussing in particular cases single Einstein Telescope (ET), ET plus two Cosmic Explorer...
ABSTRACT GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger Addicts) is a network of 25 telescopes different sizes, including both photometric and spectroscopic facilities. The aims coordinate follow-up observations gravitational-wave (GW) candidate alerts, especially those with large localization uncertainties, reduce delay between initial detection optical confirmation. In this paper, we detail GRANDMA’s observational performance during LIGO/Advanced Virgo Observing Run...
The All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) is designed to identify and characterize gamma rays from extreme explosions accelerators. main science themes include: supermassive black holes their connections neutrinos cosmic rays; binary neutron star mergers the relativistic jets they produce; ray particle acceleration sources including Galactic supernovae; continuous monitoring of other astrophysical events over full sky in this important energy range. AMEGO-X will...
The "ultra-long" gamma-ray burst GRB 111209A at redshift z = 0.677 is the longest ever observed thus far, with a rest frame prompt emission duration of ∼4 hr. In order to explain exceptional longevity, low-metallicity blue supergiant progenitor was invoked. this article we further constrain phenomenology and properties peculiar by performing multiband temporal spectral analysis both afterglow emission. We use proprietary publicly available data from Swift, Konus WIND, XMM-Newton, TAROT, as...
We estimate the stochastic gravitational wave (GW) background signal from field population of coalescing binary stellar mass black holes (BHs) throughout Universe. This study is motivated by recent observations BH-Wolf-Rayet star systems and new estimates in metallicity abundances forming galaxies that imply BH-BH are more common than previously assumed. Using analytical results inspiral-merger-ringdown waveforms for BH systems, we resulting GW signal. Assuming average quantities single...
We present the Global Rapid Advanced Network Devoted to Multi-messenger Addicts (GRANDMA). The network consists of 21 telescopes with both photometric and spectroscopic facilities. They are connected together thanks a dedicated infrastructure. aims at coordinating observations large sky position estimates transient events enhance their follow-up reduce delay between initial detection optical confirmation. GRANDMA program mainly focuses on gravitational-wave alerts find characterise...
The observational follow-up campaign of the gravitational wave (GW) multimessenger event GW170817/GRB170817A has shown that prompt gamma-rays are consistent with a relativistic structured jet observed from wide viewing angle ≳20°. We perform Bayesian inference using data early and late EM observations to determine profile GRB170817A assuming model. use geometric dependence on burst luminosity produce short-duration gamma-ray (sGRB) efficiency function redshift, which folded in binary neutron...
We investigate the prospects for joint low-latency gravitational wave (GW) detection and prompt electromagnetic (EM) follow-up observations of coalescing binary neutron stars (BNSs). For BNS mergers associated with short duration gamma-ray bursts (SGRBs), we first time evaluate feasibility rapid EM follow-ups to capture emission, early engine activity or reveal any potential by-products such as magnetars fast radio bursts. To achieve our goal, simulate a population BNSs using realistic...
Abstract Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced the presence of tides, which depend on star equation state. Neutron mergers are expected to often produce rapidly rotating remnant that emit gravitational waves. These will provide clues extremely hot post-merger environment. This signature in contains most 2–4 kHz frequency band, outside sensitive...
We employ realistic constraints on astrophysical and instrumental selection effects to model the Gamma-Ray Burst (GRB) redshift distribution using {\it Swift} triggered samples acquired from optical afterglows (OA) TOUGH survey. Models for Malmquist bias, desert, fraction of missing because host galaxy dust extinction, are used show how "true" GRB is distorted its presently observed biased distribution. also investigate another effect arising a correlation between $E_{{\rm iso}}$ $L_{{\rm...
We assess the detection prospects of a gravitational wave background associated with sub-luminous gamma-ray bursts (SL-GRBs). assume that central engines significant proportion these are provided by newly born magnetars and consider two plausible GW emission mechanisms. Firstly, deformation-induced triaxial from magnetar. Secondly, onset secular bar-mode instability, long lived plateau observed in X-ray afterglows many (Corsi & Meszaros 2009a). With regards to detectability, we find...
The upper limit on the energy density of a stochastic gravitational wave (GW) background obtained from two-year science run (S5) Laser Interferometer Gravitational-wave Observatory (LIGO) is used to constrain average GW production core collapse supernovae (ccSNe). We assume that ccSNe rate tracks star formation history universe and show depends only weakly assumed source spectrum. Using for $z\leq10$, we scale generic spectrum obtain an observation-based emission. mean emitted in GWs can be...
We compute the intrinsic isotropic peak luminosity function (LF) and formation rate of long gamma-ray bursts (LGRBs) using a novel approach. complement standard log\,$N$\,--\,log\,$P$ brightness distribution $V_{\mathrm{max}}$ estimations with two observation-time relations: redshift--observation-time relation (log\,$z$\,--\,log\,$T$) new luminosity--observation-time (log\,$L$\,--\,log\,$T$). show that this approach reduces degeneracies exist between LF distribution. To account for complex...
Intense flares that occur at late times relative to the prompt phase have been observed by $Swift$ satellite in X-ray afterglows of gamma-ray bursts (GRBs). Here, we present a detailed analysis on fall back accretion process explain intense flare very early afterglow light curves. To reproduce times, resort external shock engaging energy injections. By applying our model GRBs 080810, 081028 and 091029, show their curves can be reproduced well. We then apply ultra-long GRB 111209A, which is...
Abstract Multi-messenger astrophysics is becoming a major avenue to explore the Universe, with potential span vast range of redshifts. The growing synergies between different probes opening new frontiers, which promise profound insights into several aspects fundamental physics and cosmology. In this context, THESEUS will play central role during 2030s in detecting localizing electromagnetic counterparts gravitational wave neutrino sources that unprecedented sensitivity next generation...
We present calculations of the stochastic gravitational wave (GW) background resulting from neutron star birth throughout Universe. update previous by employing three GW waveforms Dimmelmeier, Font & Müller, based on models incorporating general relativistic effects for axisymmetric core collapse rotating massive stars. Source-rate evolution is accounted using a simulated formation rate model 'flat-Λ' cosmology given Hernquist Springel. show that only weakly dependent source-rate model....
Abstract The new 1 m f/4 fast-slew Zadko Telescope was installed in June 2008 about 70 km north of Perth, Western Australia. It is the only metre-class optical facility at this southern latitude between east coast Australia and South Africa, can rapidly image transients a longitude not monitored by other similar facilities. We report on first imaging tests pilot program minor planet searches, Target Opportunity observations triggered Swift satellite. In 12 months, 6 gamma-ray burst...
This paper describes the proposed AIGO detector for worldwide array of interferometric gravitational wave detectors.The first part summarizes benefits that provides to second gives a technical description detector, which will follow closely Advanced LIGO design.Possible variations in design are discussed.