M. E. Lower
A5083492013- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Astronomical Observations and Instrumentation
- Atomic and Subatomic Physics Research
- Stellar, planetary, and galactic studies
- Magnetic confinement fusion research
- GNSS positioning and interference
- Superconducting Materials and Applications
- Geophysics and Sensor Technology
- High-pressure geophysics and materials
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Nuclear Physics and Applications
- Advanced Frequency and Time Standards
- Medical Imaging Techniques and Applications
- Inertial Sensor and Navigation
- Seismic Waves and Analysis
- Astro and Planetary Science
- Gyrotron and Vacuum Electronics Research
- Black Holes and Theoretical Physics
Swinburne University of Technology
2018-2025
Commonwealth Scientific and Industrial Research Organisation
2019-2025
Australia Telescope National Facility
2019-2025
ARC Centre of Excellence for All-sky Astrophysics
2024
Astronomy and Space
2019-2023
ARC Centre of Excellence for Gravitational Wave Discovery
2018-2022
Astronomy Australia
2022
Australian Research Council
2020
Monash University
2018-2019
Bayesian parameter estimation is fast becoming the language of gravitational-wave astronomy. It method by which data used to infer sources' astrophysical properties. We introduce a user-friendly inference library for astronomy, Bilby. This python code provides expert-level infrastructure with straightforward syntax and tools that facilitate use beginners. allows users perform accurate reliable on both real, freely-available from LIGO/Virgo, simulated data. provide suite examples analysis...
Abstract Pulsar timing arrays aim to detect nanohertz-frequency gravitational waves (GWs). A background of GWs modulates pulsar arrival times and manifests as a stochastic process, common all pulsars, with signature spatial correlation. Here we describe search for an isotropic gravitational-wave (GWB) using observations 30 millisecond pulsars from the third data release Parkes Timing Array (PPTA), which spans 18 yr. Using current Bayesian inference techniques recover characterize...
ABSTRACT Gravitational waves provide a unique tool for observational astronomy. While the first LIGO–Virgo catalogue of gravitational-wave transients (GWTC-1) contains 11 signals from black hole and neutron star binaries, number observations is increasing rapidly as detector sensitivity improves. To extract information observed signals, it imperative to have fast, flexible, scalable inference techniques. In previous paper, we introduced bilby: modular user-friendly Bayesian library adapted...
Abstract We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. is a high-gain ( ${\sim}2.8\,\mbox{K Jy}^{-1}$ ) low-system temperature ${\sim}18\,\mbox{K at }20\,\mbox{cm}$ array that currently operates 580–1 670 MHz can produce tied-array beams suitable observations. This paper presents MeerTime Large Survey Project commissioning with PTUSE. Highlights include...
Abstract We present the third data release from Parkes Pulsar Timing Array (PPTA) project. The contains observations of 32 pulsars obtained using 64-m ‘Murriyang’ radio telescope. span is up to 18 yr with a typical cadence 3 weeks. This formed by combining an updated version our second $\sim$ more recent primarily ultra-wide-bandwidth receiver system that operates between 704 and 4032 MHz. provide calibrated pulse profiles, flux density dynamic spectra, times arrival, initial pulsar timing...
The noise in millisecond pulsar (MSP) timing data can include contributions from observing instruments, the interstellar medium, solar wind, system ephemeris errors, and pulsars themselves. environment must be accurately characterized order to form null hypothesis which signal models compared, including signature induced by nanohertz-frequency gravitational waves (GWs). Here we describe developed for each of MSPs Parkes Pulsar Timing Array (PPTA) third release, have been used as basis a...
Abstract We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on Fermi Gamma-ray Space Telescope. Another 33 millisecond (MSPs) discovered deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems colocated with also harbor gamma-ray MSPs. This catalog thus reports roughly 340 and candidates, 10% all known pulsars, compared to ≤11 before Fermi. Half...
Abstract We describe 14 yr of public data from the Parkes Pulsar Timing Array (PPTA), an ongoing project that is producing precise measurements pulse times arrival 26 millisecond pulsars using 64-m radio telescope with a cadence approximately 3 weeks in three observing bands. A comprehensive description pulsar systems employed at since 2004 provided, including calibration methodology and analysis stability system components. attempt to provide full accounting reduction raw measured Stokes...
When binary black holes form in the field, it is expected that their orbits typically circularize before coalescence. In galactic nuclei and globular clusters, can dynamically. Recent results suggest $\ensuremath{\approx}5%$ of mergers clusters result from three-body interactions. These interactions are to induce significant orbital eccentricity $\ensuremath{\gtrsim}0.1$ when they enter Advanced LIGO Virgo band at a gravitational-wave frequency 10 Hz. Measurements hole therefore provide...
ABSTRACT The mechanism that produces fast radio burst (FRB) emission is poorly understood. Targeted monitoring of repeating FRB sources provides the opportunity to fully characterize properties in a manner impossible with one-off bursts. Here, we report observations source 20201124A, Australian Square Kilometre Array Pathfinder (ASKAP) and ultra-wideband low (UWL) receiver at Parkes 64-m telescope (Murriyang). entered period emitting bright bursts during early 2021 April. We have detected 16...
Long-period radio transients are an emerging class of extreme astrophysical events which only three known. These objects emit highly polarised, coherent pulses typically a few tens seconds duration and minutes to hour-long periods. While magnetic white dwarfs magnetars, either isolated or in binary systems, have been invoked explain these objects, consensus has not emerged. Here we report on the discovery ASKAP J193505.1+214841.0 (henceforth ASKAPJ1935+2148) with period 53.8 exhibiting...
While pulsars possess exceptional rotational stability, large scale timing studies have revealed at least two distinct types of irregularities in their rotation: red noise and glitches. Using modern Bayesian techniques, we investigated the properties 300 bright southern-sky radio that been observed over 1.0-4.8 years by upgraded Molonglo Observatory Synthesis Telescope (MOST). We reanalysed spin spin-down changes associated with nine previously reported pulsar glitches, report discovery...
We detail a new fast radio burst (FRB) survey with the Molonglo Radio Telescope, in which six FRBs were detected between June 2017 and December 2018. By using real-time FRB detection system, we captured raw voltages for five of events, allowed coherent dedispersion very high time resolution (10.24 $\mu$s) studies bursts. Five show temporal broadening consistent interstellar and/or intergalactic scattering, scattering timescales ranging from 0.16 to 29.1 ms. One burst, FRB181017, shows...
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 Radio emission from magnetars provides a unique probe of the relativistic, magnetized plasma within near-field environment these ultra-magnetic neutron stars. The transmitted waves can undergo birefringent and dispersive propagation effects that result in frequency-dependent conversions linear to circularly polarized radiation vice versa, thus necessitating classification when relating measured polarization intrinsic properties star fast radio burst sites. We report detection such...
Abstract The soft-gamma repeater Swift J1818.0−1607 is only the fifth magnetar found to exhibit pulsed radio emission. Using Ultra-Wideband Low receiver system of Parkes telescope, we conducted a 3 hr observation J1818.0−1607. Folding data at rotation period P = 1.363 s, obtained wideband polarization profiles and flux density measurements covering frequencies between 704 4032 MHz. After measuring, then correcting for pulsar’s measure 1442.0 ± 0.2 rad m −2 , find profile 80% 100% linearly...
We describe the ongoing Relativistic Binary programme (RelBin), a part of MeerTime large survey project with MeerKAT radio telescope. RelBin is primarily focused on observations relativistic effects in binary pulsars to enable measurements neutron star masses and tests theories gravity. selected 25 as an initial high priority list targets based their characteristics observational history other telescopes. In this paper, we provide outline programme, present polarisation calibrated pulse...
Abstract The Galactic center is host to a population of extraordinary radio filaments, thin linear structures that trace out magnetic field lines running perpendicular the plane. Using Murriyang, 64 m Parkes telescope, we conducted search for pulsars centered on position compact source in filament G359.0−0.2. We discovered millisecond pulsar (MSP), PSR J1744−2946, with period P = 8.4 ms, bound 4.8 hr circular orbit around an M c > 0.05 ⊙ companion. dispersion measure 673.7 ± 0.1 pc cm −3...
Abstract A nanohertz-frequency stochastic gravitational-wave background can potentially be detected through the precise timing of an array millisecond pulsars. This produces low-frequency noise in pulse arrival times that would have a characteristic spectrum common to all pulsars and well-defined spatial correlation. Recently North American Nanohertz Observatory for Gravitational Waves collaboration (NANOGrav) found evidence common-spectrum component their 12.5 yr data set. Here we report on...
ABSTRACT Magnetars are a promising candidate for the origin of fast radio bursts (FRBs). The detection an extremely luminous burst from Galactic magnetar SGR J1935+2154 on 2020 April 28 added credence to this hypothesis. We report simultaneous and non-simultaneous observing campaigns using Arecibo, Effelsberg, LOFAR, MeerKAT, MK2, Northern Cross telescopes MeerLICHT optical telescope in days months after event. did not detect any significant single pulses down fluence limits between 25 mJy...
ABSTRACT The radio polarization properties of the pulsar population are only superficially captured by conventional picture emission. We study broadband 271 young pulsars, focusing particularly on circular polarization, using high-quality observations made with Ultra-Wideband Low receiver Murriyang, Parkes telescope. seek to encapsulate behaviour a scale defining broad categories for frequency- and phase-dependent evolution, studying co-occurrences these categorizations comparing them...
We present the third data release from Parkes Pulsar Timing Array (PPTA) project. The contains observations of 32 pulsars obtained using 64-m "Murriyang" radio telescope. span is up to 18 years with a typical cadence 3 weeks. This formed by combining an updated version our second $\sim 3$ more recent primarily ultra-wide-bandwidth receiver system that operates between 704 and 4032 MHz. provide calibrated pulse profiles, flux-density dynamic spectra, times arrival, initial pulsar timing...
The study of impulsive astrophysical radio emission makes it possible to probe the intervening plasma between source and Earth. In cold electron-ion plasmas, circular propagating wave modes primarily alter linear polarization plane that scales with inverse-square frequency. relativistic are elliptically polarized, is convert linearly polarized into vice versa. Fast bursts (FRBs) enable not only intergalactic medium but potentially extreme magneto-ionic in which these intense pulses produced....
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...