S. Johnston
A5045533942- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Astrophysical Phenomena and Observations
- High-pressure geophysics and materials
- Stellar, planetary, and galactic studies
- Neutrino Physics Research
- Advanced Frequency and Time Standards
- Dark Matter and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Geophysics and Sensor Technology
- Superconducting Materials and Applications
- Atomic and Subatomic Physics Research
- Particle physics theoretical and experimental studies
- GNSS positioning and interference
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Genetic and phenotypic traits in livestock
- Galaxies: Formation, Evolution, Phenomena
- Sperm and Testicular Function
- Reproductive Physiology in Livestock
Australia Telescope National Facility
2016-2025
Commonwealth Scientific and Industrial Research Organisation
2016-2025
The University of Queensland
2007-2025
Durham University
2025
Reitaku University
2025
Astronomy and Space
2015-2024
University of Massachusetts Amherst
2014-2022
Argonne National Laboratory
2018-2021
Agriculture and Food
2011-2021
ARC Centre of Excellence for All-sky Astrophysics
2020
Searches for transient astrophysical sources often reveal unexpected classes of objects that are useful physical laboratories. In a recent survey pulsars and fast transients we have uncovered four millisecond-duration radio all more than 40{\deg} from the Galactic plane. The bursts' properties indicate they celestial rather terrestrial origin. Host galaxy intergalactic medium models suggest cosmological redshifts 0.5 to 1, distances up 3 gigaparsecs. No temporally coincident x- or gamma-ray...
We report the first measurement of parity-violating asymmetry APV in elastic scattering polarized electrons from Pb208. is sensitive to radius neutron distribution (Rn). The result APV=0.656±0.060(stat)±0.014(syst) ppm corresponds a difference between radii and proton distributions Rn−Rp=0.33−0.18+0.16 fm provides electroweak observation skin which expected heavy, neutron-rich nucleus.Received 12 January 2012DOI:https://doi.org/10.1103/PhysRevLett.108.112502© 2012 American Physical Society
We report a precision measurement of the parity-violating asymmetry $A_{PV}$ in elastic scattering longitudinally polarized electrons from $^{208}$Pb. measure $A_{PV}=550\pm 16 {\rm (stat)}\pm 8\ (syst)}$ parts per billion, leading to an extraction neutral weak form factor $F_W(Q^2 = 0.00616\ GeV}^2) 0.368 \pm 0.013$. Combined with our previous measurement, extracted neutron skin thickness is $R_n-R_p=0.283 0.071$~fm. The result also yields first significant direct interior density...
The dramatic increase in the number of known gamma-ray pulsars since launch Fermi Gamma-ray Space Telescope (formerly GLAST) offers first opportunity to study a sizable population these high-energy objects. This catalog summarizes 46 high-confidence pulsed detections using six months data taken by Large Area (LAT), Fermi's main instrument. Sixteen previously unknown were discovered searching for signals at positions bright sources seen with LAT, or objects suspected be neutron stars based on...
Here we describe the Compact Array Broadband Backend (CABB) and present first results obtained with upgraded Australia Telescope (ATCA). The 16-fold increase in observing bandwidth, from 2 x 128 MHz to 2048 MHz, high bit sampling, addition of 16 zoom windows (each divided into a further channels) provide major improvements for all ATCA observations. benefits new system are: (1) hugely increased radio continuum polarization sensitivity as well image fidelity, (2) substantially improved...
Fast radio bursts (FRBs) are one of the most tantalizing mysteries sky; their progenitors and origins remain unknown until now no rapid multiwavelength follow-up an FRB has been possible. New instrumentation decreased time between observation discovery from years to seconds, enables polarimetry be performed on FRBs for first time. We have discovered (FRB 140514) in real-time 14 May, 2014 at 17:14:11.06 UTC Parkes telescope triggered other wavelengths within hours event. 140514 was found with...
Abstract The detection of five new fast radio bursts (FRBs) found in the 1.4-GHz High Time Resolution Universe high-latitude survey at Parkes, is presented. rate implied 7$^{+5}_{-3}\times 10^3$ (95 per cent) FRBs sky−1 d−1 above a fluence 0.13 Jy ms for an FRB 0.128 duration to 1.5 16 duration. One these has two-component profile, which each component similar known population single and two components are separated by 2.4 ± 0.4 ms. All appear be unresolved following deconvolution with...
Results from a search for neutrinoless double-beta decay (0νββ) of ^{136}Xe are presented using the first year data taken with upgraded EXO-200 detector. Relative to previous searches by EXO-200, energy resolution detector has been improved σ/E=1.23%, electric field in drift region raised 50%, and system suppress radon volume between cryostat lead shielding implemented. In addition, analysis techniques that improve topological discrimination 0νββ background events have developed....
In this paper we describe the system design and capabilities of Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope at conclusion its construction project commencement science operations. ASKAP is one first telescopes to deploy phased array feed (PAF) technology on a large scale, giving it an instantaneous field view that covers 31 square degrees 800 MHz. As two-dimensional 36x12m antennas, with baselines ranging from 22m 6km, also has excellent snapshot imaging capability...
Fast radio bursts (FRBs) are millisecond-duration events thought to originate beyond the Milky Way galaxy. Uncertainty surrounding burst sources, and their propagation through intervening plasma, has limited use as cosmological probes. We report on a mildly dispersed (dispersion measure 266.5+-0.1 pc cm^-3), exceptionally intense (120+-30 Jy), linearly polarized, scintillating (FRB 150807) that we directly localize 9 arcmin^2. Based low Faraday rotation (12.0+-0.7 rad m^-2), infer negligible...
We report a precise measurement of the parity-violating (PV) asymmetry A_{PV} in elastic scattering longitudinally polarized electrons from ^{48}Ca. measure A_{PV}=2668±106(stat)±40(syst) parts per billion, leading to an extraction neutral weak form factor F_{W}(q=0.8733 fm^{-1})=0.1304±0.0052(stat)±0.0020(syst) and charge minus F_{ch}-F_{W}=0.0277±0.0055. The resulting neutron skin thickness R_{n}-R_{p}=0.121±0.026(exp)±0.024(model) fm is relatively thin yet consistent with many model...
We present a study of the spectral properties 441 pulsars observed with Parkes radio telescope near centre frequencies 728, 1382 and 3100 MHz. The observations at 728 MHz were conducted simultaneously using dual-band 10-50cm receiver. These high-sensitivity, multi-frequency provide systematic uniform sample pulsar flux densities. combine our measurements data from literature in order to derive these pulsars. Using techniques robust regression information theory we classify spectra an...
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....
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 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...
We report the discovery of very-high-energy (VHE) γ-ray emission binary system PSR B1259-63/SS 2883 a radio pulsar orbiting massive, luminous Be star in highly eccentric orbit.The observations around 2004 periastron passage were performed with four 13 m Cherenkov telescopes HESS experiment, recently installed Namibia and full operation since December 2003.Between February June 2004, signal from was detected total significance above 13σ.The flux found to vary significantly on timescales days...
view Abstract Citations (349) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS PSR 1259-63: A Binary Radio Pulsar with a Be Star Companion Johnston, Simon ; Manchester, R. N. Lyne, A. G. Bailes, M. Kaspi, V. Qiao, Guojun D'Amico, The discovery of the first known radio pulsar massive, nondegenerate companion is reported. 1259-63, found during large-scale high-frequency survey southern Galactic plane, has period 47 ms and pulse profile similar to...
Abstract The future of centimetre and metre-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by consortium 17 countries that will be 50 times more sensitive than any existing radio facility. Most key science for SKA addressed through large-area imaging Universe at frequencies from few hundred MHz to GHz. Australian Pathfinder (ASKAP) is technology demonstrator aimed in mid-frequency range, achieves instantaneous wide-area deployment phased-array feed...
We report on gamma-ray observations of the Crab Pulsar and Nebula using 8 months survey data with Fermi Large Area Telescope (LAT). The high quality light curve obtained ephemeris provided by Nancay Jodrell Bank radio telescopes shows two main peaks stable in phase energy. first peak leads pulse (281 \pm 12 21) mus, giving new constraints production site non-thermal emission pulsar magnetospheres. improved sensitivity unprecedented statistics afforded LAT enable precise measurement spectral...
The Australia SKA Pathfinder (ASKAP) is a new telescope under development as world-class high-dynamic-range wide-field-of-view survey instrument. It will utilize focal plane phased array feeds on the 36 12-m antennas that compose array. large amounts of data present huge computing challenge, and ASKAP store products in an archive after near real-time pipeline processing. This powerful instrument be deployed at radio-quiet observatory, Murchison Radio-astronomy Observatory midwest region...