A5006496948- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Astrophysical Phenomena and Observations
- High-pressure geophysics and materials
- Cosmology and Gravitation Theories
- Magnetic confinement fusion research
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Advanced Frequency and Time Standards
- Inertial Sensor and Navigation
- Atomic and Subatomic Physics Research
- Ionosphere and magnetosphere dynamics
- Seismic Imaging and Inversion Techniques
- Statistical Mechanics and Entropy
- Astronomical Observations and Instrumentation
- Particle physics theoretical and experimental studies
- Black Holes and Theoretical Physics
- Mechanical and Optical Resonators
- Astro and Planetary Science
- earthquake and tectonic studies
- Superconducting Materials and Applications
- Dark Matter and Cosmic Phenomena
ARC Centre of Excellence for Gravitational Wave Discovery
2020-2025
The University of Melbourne
2019-2025
Australian Research Council
2020-2023
Monash University
2017
ABSTRACT We report on a timing programme of 74 young pulsars that have been observed by the Parkes 64-m radio telescope over past decade. Using modern Bayesian techniques, we measured properties 124 glitches in 52 these pulsars, which are new. demonstrate glitch sample is complete to fractional increases spin frequency greater than $\Delta \nu ^{90{{\ \rm per\ cent}}}_{\mathrm{ g}}/\nu \approx 8.1 \times 10^{-9}$ . measure values braking index, n, 33 pulsars. In most their rotational...
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...
Abstract The stochastic gravitational wave background (SGWB) can be observed in the nanohertz band using a pulsar timing array (PTA). Here computationally efficient state-space framework is developed for analysing SGWB data, which strain at Earth tracked with non-linear Kalman filter and separated simultaneously from intrinsic, achromatic spin wandering. combined nested sampler to estimate parameters of model, calculate Bayes factor selecting between models without SGWB. procedure extends...
Abstract We report the radio and high-energy properties of a new outburst from radio-loud magnetar 1E 1547.0−5408. Following detection short burst source with Swift-BAT on 2022 April 7, observations by NICER detected an increased flux peaking at (6.0 ± 0.4) × 10 −11 erg s −1 cm −2 in soft X-ray band, falling to baseline level 1.7 over 17 day period. Joint spectroscopic measurements NuSTAR indicated no change hard nonthermal tail despite prominent increase X-rays. Observations wavelengths...
Low mass x-ray binaries are prime targets for continuous gravitational wave searches by ground-based interferometers. Results presented from a search five low-mass whose spin frequencies and orbital elements measured accurately pulsations: HETE J1900.1-2455, IGR $\mathrm{J}00291+5934$, SAX J1808.4-3658, XTE J0929-314, J1814-338. Data analysed Observing Run 2 of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). The algorithm uses hidden Markov model to track wandering,...
We pursue a novel strategy toward first detection of continuous gravitational waves from rapidly rotating deformed neutron stars. Computational power is focused on narrow region signal parameter space selected by strategically chosen benchmark. search data the second observing run LIGO Observatory with an optimized analysis graphics processing units. While no are detected, achieves sensitivity to wave strain ${h}_{0}=1.01\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}$ at 90%...
Isolated neutron stars are prime targets for continuous-wave (CW) searches by ground-based gravitational-wave interferometers. Results presented from a CW search targeting ten pulsars. The uses semicoherent algorithm, which combines the maximum-likelihood $\mathcal{F}$-statistic with hidden Markov model (HMM) to efficiently detect and track quasi-monochromatic signals wander randomly in frequency. targets, associated TeV sources detected High Energy Stereoscopic System (H.E.S.S.), chosen...
Radio pulsar glitches probe far-from-equilibrium processes involving stress accumulation and relaxation in neutron star interiors. Previous studies of glitch rates have focused on individual pulsars with as many recorded possible. In this work we analyze using all available data including objects that glitched never or once. We assume the rate follows a homogeneous Poisson process, therefore exclude which exhibit quasiperiodic glitching behavior. Calculating relevant Bayes factors shows...
A systematic, semi-automated search for pulsar glitches in the first UTMOST public data release is presented. The carried out using a hidden Markov model which incorporates both and timing noise into of assumed phase evolution pulsar. Glitches are detected through Bayesian selection between models with without present minimal human intervention. Nine among seven objects, all have been previously reported. No new were detected. Injection studies used to place 90\% frequentist upper limits on...
We present a comprehensive study of the rotational and emission properties PSR J0738$-$4042 using combination observations taken by Deep Space Network, Hartebeesthoek, Parkes (Murriyang) Molonglo observatories between 1972 2023. Our timing pulsar is motivated previously reported profile/spin-down events that occurred in September 2005 December 2015, which result an anomalously large braking index $n = 23300 \pm 1800$. Using Gaussian process regression framework, we develop continuous models...
Following up large numbers of candidates in continuous gravitational-wave searches presents a challenge, particularly regard to computational power and the time required manually scrutinize each candidates. It is important design test good follow-up procedures that are safe (i.e., minimize false dismissals) computationally efficient across many search configurations. We investigate two procedures, or ``vetoes,'' both which exploit Doppler modulation predicted astrophysical signals. In...
We calculate the baryon asymmetry of Universe in Z3-invariant Next-to-Minimal Supersymmetric Standard Model where interactions singlino provide necessary source charge and parity violation. Using closed time path formalism, we derive solve transport equations for cases singlet acquires a vacuum expectation value (VEV) before during electroweak phase transition. perform detailed scan to show how varies throughout relevant parameter space. Our results that case VEV transition typically...
A striking feature of the Vela pulsar (PSR J0835$-$4510) is that it undergoes sudden increases in its spin frequency, known as glitches, with a fractional amplitude on order $10^{-6}$ approximately every 900 days. Glitches smaller magnitudes are also to occur Vela. Their distribution both time and less well constrained but equally important for understanding physical process underpinning these events. In better understand small glitches Vela, an analysis high-cadence observations from Mount...
Continuous nanohertz gravitational waves from individual supermassive black hole binaries may be detectable with pulsar timing arrays. A novel search strategy is developed, wherein intrinsic achromatic spin wandering tracked simultaneously the modulation induced by a single wave source in pulse times of arrival. two-step inference procedure applied within state-space framework, such that Kalman filter, which then provides likelihood for nested sampling. The estimates static parameters...
We present a search for continuous gravitational-wave signals from an unidentified pulsar potentially powering HESS J1427-608, spatially unresolved TeV point source detected by the High Energy Stereoscopic System (HESS). The uses semicoherent algorithm, which combines maximum likelihood $\mathcal{F}$ statistic with hidden Markov model to efficiently detect and track quasimonochromatic that wander randomly in frequency. It data second observing run of Advanced Laser Interferometer...
Abstract Pulsar timing experiments typically generate a phase-connected solution from sequence of times arrival (TOAs) by absolute pulse numbering, i.e., fitting an integer number pulses between TOAs in order to minimize the residuals with respect parameterized phase model. In this observing mode, rotational glitches are discovered, when no-glitch model diverge after some epoch, and glitch parameters refined Bayesian follow-up. Here, we present alternative, complementary approach which...
ABSTRACT In certain pulsar timing experiments, where observations are scheduled approximately periodically (e.g. daily), models with significantly different frequencies (including but not limited to glitch frequency increments) return near-equivalent residuals. The average scheduling aperiodicity divided by the phase error due time-of-arrival uncertainties is a useful indicator when degeneracy important. Synthetic data used explore effect of this systematically. It found that phase-coherent...
ABSTRACT Continuous nanohertz gravitational waves from individual supermassive black hole binaries may be detectable with pulsar timing arrays. A novel search strategy is developed, wherein intrinsic achromatic spin wandering tracked simultaneously the modulation induced by a single wave source in pulse times of arrival. two-step inference procedure applied within state-space framework, such that Kalman filter, which then provides likelihood for nested sampling. The estimates static...
We present results of a follow-up search for continuous gravitational waves (CWs) associated with subthreshold candidates from the LIGO-Virgo-KAGRA (LVK) all-sky all-frequency (ASAF) directed radiometer analysis, using Advanced LIGO data third observing run (O3). Each ASAF candidate corresponds to $1/32\text{ }\text{ }\mathrm{Hz}$ frequency band and $\ensuremath{\sim}13\text{ }{\mathrm{deg}}^{2}$ sky pixel. Assuming they represent possible CW sources, we analyze all 515 semi-coherent,...
ABSTRACT The Molonglo Cross was first commissioned in 1965, as a transit radio (408 MHz) interferometer with the largest collecting area Southern hemisphere. In 1981, telescope redeveloped an Earth-rotation synthesis using only East–West arm (843 MHz), known Observatory Synthesis Telescope. While revitalized 2010s, (slightly larger) North–South (NS) arm, which consists of two co-linear paraboloid cylindrical reflectors spanning 2 × 778 m 12.7 m, had not been used for over 40 yr. Re-fitting...
ABSTRACT Pulsar timing arrays (PTA) can detect continuous nanohertz gravitational waves (GW) emitted by individual supermassive black hole binaries. The data analysis procedure be formulated within a time-domain, state-space framework, in which the radio observations are related to temporal sequence of latent states, namely intrinsic pulsar spin frequency. achromatic wandering frequency is tracked using Kalman filter concurrently with pulse modulation induced GW from single source. sum terms...
Pulsar timing arrays can detect continuous nanohertz gravitational waves emitted by individual supermassive black hole binaries. The data analysis procedure be formulated within a time-domain, state-space framework, in which the radio observations are related to temporal sequence of latent states, namely intrinsic pulsar spin frequency. achromatic wandering frequency is tracked using Kalman filter concurrently with pulse modulation induced wave from single source. sum terms proportional...
The $\mathcal{F}$-statistic is a detection statistic used widely in searches for continuous gravitational waves with terrestrial, long-baseline interferometers. A new implementation of the presented which accelerates existing "resampling" algorithm using graphics processing units (GPUs). runs between 10 and 100 times faster than on central without sacrificing numerical accuracy. utility GPU demonstrated pilot narrowband search four newly discovered millisecond pulsars globular cluster Omega...
We present a comprehensive study of the rotational and emission properties PSR J0738$-$4042 using combination observations taken by Deep Space Network, Hartebeesthoek, Parkes (Murriyang) Molonglo observatories between 1972 2023. Our timing pulsar is motivated previously reported profile/spin-down events that occurred in September 2005 December 2015, which result an anomalously large braking index $n = 23300 \pm 1800$. Using Gaussian process regression framework, we develop continuous models...