A5077641754- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- GNSS positioning and interference
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Particle Accelerators and Free-Electron Lasers
- Astrophysics and Star Formation Studies
- Neutrino Physics Research
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Dark Matter and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Semiconductor Lasers and Optical Devices
- Superconducting and THz Device Technology
- Astro and Planetary Science
- Laser-Plasma Interactions and Diagnostics
- Adaptive optics and wavefront sensing
- Optical Systems and Laser Technology
- Particle Detector Development and Performance
Commonwealth Scientific and Industrial Research Organisation
2016-2024
Astronomy and Space
2016-2024
SKA Observatory
2019
International Centre for Radio Astronomy Research
2009-2016
Curtin University
2009-2016
Australia Telescope National Facility
2016
University of California, Berkeley
2015
Jet Propulsion Laboratory
2015
Max Planck Innovation
2014
Max Planck Society
2014
The binary neutron star merger event GW170817 was detected through both electromagnetic radiation and gravitational waves. Its afterglow emission may have been produced by either a narrow relativistic jet or an isotropic outflow. High-spatial-resolution measurements of the source size displacement can discriminate between these scenarios. We present very-long-baseline interferometry observations, performed 207.4 days after using global network 32 radio telescopes. apparent is constrained to...
Abstract The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an unprecedented opportunity to investigate the transient sky at radio wavelengths. In this paper we present VAST, ASKAP survey for Variables and Slow Transients. VAST exploit wide-field capabilities of enable discovery investigation variable phenomena from local cosmological, including flare stars, intermittent pulsars, X-ray binaries, magnetars, extreme scattering events, interstellar scintillation, supernovae,...
Abstract Multiwavelength polarimetry and radio observations of Swift J1727.8–1613 at the beginning its recent 2023 outburst suggested presence a bright compact jet aligned in north–south direction, which could not be confirmed without high-angular-resolution images. Using Very Long Baseline Array Array, we imaged during hard/hard-intermediate state, revealing core large, two-sided, asymmetrical, resolved jet. The extends position angle −0.60° ± 0.07° east north. At 8.4 GHz, entire structure...
Coordinated ground‐based observations of Titan were performed around or during the Huygens atmospheric probe mission at on 14 January 2005, connecting momentary in situ by with synoptic coverage provided continuing programs. These consisted three different categories: (1) radio telescope tracking signal 2040 MHz, (2) atmosphere and surface Titan, (3) attempts to observe radiation emitted Probe entry into Titan's atmosphere. The was successfully acquired a network terrestrial telescopes,...
The detection of seven fast radio bursts (FRBs) has recently been reported. FRBs are short duration (∼1 ms), highly dispersed pulses from astronomical sources. physical interpretation for the remains unclear but is thought to involve compact objects at cosmological distance. It suggested that a fraction could be physically associated with gamma-ray (GRBs). Recent observations GRBs have reported two using 12 m telescope 1.4 GHz. Motivated by this result, we performed systematic and sensitive...
Extreme scattering events (ESEs) are distinctive fluctuations in the brightness of astronomical radio sources caused by occulting plasma lenses interstellar medium. The inferred pressures ~10(3) times ambient pressure, challenging our understanding gas conditions Milky Way. Using a new survey technique, we discovered an ESE while it was progress. Here report and optical follow-up observations. Modeling data demonstrates that lensing structure is density enhancement lens diverging, ruling out...
We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part Nearby AGN Key Science Program, source was observed in Feb 2014 at with 21 ground stations, reaching projected $(u,v)$-spacings up to $\sim11\,$G$\lambda$. The experiment complemented snapshot RadioAstron data obtained during 2013--2016 Survey Program. Their longest baselines extend $\sim25\,$G$\lambda$. For all these measurements, fringes are...
There is growing evidence of relativistic jets in radio-loud narrow-line Seyfert 1 (RL-NLS1) galaxies. We constrain the observational properties radio emission first RL-NLS1 galaxy ever detected gamma-rays, PMN J0948+0022, i.e., its flux density and structure total intensity polarization, compactness, variability. performed three real-time e-VLBI observations J0948+0022 at 22 GHz, using a global array including telescopes Europe, East Asia, Australia. These are science carried out with...
Wereportthefirstmulti-epochmilliarcsecondresolutionimagingofthe6.7-GHzclassIImethanolmaseremissionassociated with the high-mass protocluster system NGC6334I. The observations cover 4 epochs over a 10-year period between March 2010 and 2020. We confirm emergence of number new regions 6.7-GHz methanol maser emission in molecular gas surrounding NGC6334-MM1, which lies north previously known class II sites are associated NGC6334-MM3 -MM2. is located close to strongest (sub)millimetre source...
We present the discovery of radio afterglow most distant ultra-long gamma-ray burst (GRB) detected to date, GRB~220627A at redshift $z=3.084$. Its prompt light curve shows a double-pulse profile, with pulses separated by period quiescence lasting ${\sim} 15\,$min, leading early speculation it could be strongly gravitationally lensed GRB. However, our analysis $\textit{Fermi}$/GBM spectra taken during time intervals both show clear differences in their spectral energy distributions,...
We have conducted the first parallax and proper motion measurements of 6.7 GHz methanol maser emission using Australian Long Baseline Array (LBA). The G339.884$-$1.259 measured from five epochs observations is 0.48$\pm $0.08 mas, corresponding to a distance $2.1^{+0.4}_{-0.3}$ kpc, placing it in Scutum spiral arm. This consistent (within combined uncertainty) with kinematic estimate for this source at 2.5$\pm $0.5 kpc latest Solar Galactic rotation parameters. find Lyman continuum photon...
Abstract We report the first observation of nearby giant radio galaxy NGC 315 using a global very long baseline interferometry (VLBI) array consisting 22 antennas located across five continents, including high-sensitivity stations, at GHz. Utilizing extensive u v -coverage provided by array, coupled with application recently developed superresolution imaging technique based on regularized maximum-likelihood method, we were able to transversely resolve jet parsec scales for time. Previously...
We report on the first high frequency VLBI observations of nearby broad absorption line quasar (BALQSO), Mrk 231. Three epochs were achieved at 15 GHz and 22 GHz, two these included 43 as well. The nuclear radio source is resolved a compact double. core component experienced strong flare in which flux density increased by $> 150%$ (45 mJy) three months. Theoretical models imply that emission likely enhanced very Doppler boosting highly relativistic ejecta with kinetic energy flux, $Q \sim 3...
We present the results of a survey for intervening 21cm HI absorption in sample 10 nearby, gas-rich galaxies selected from Parkes All-Sky Survey (HIPASS). This follows six HIPASS searched previous work and completes our full sample. In this paper we along 17 sightlines with impact parameters between 6 46 kpc, making one new detection. also obtained simultaneous emission-line data, allowing us to directly relate absorption-line detection rate distribution. From find majority non-detections...
We investigate the origin of parsec-scale radio emission from changing-look active galactic nucleus (AGN) Mrk 590, and examine whether power has faded concurrently with dramatic decrease in accretion rates observed between 1990s present. detect a compact core at 1.6 GHz 8.4 using new Very Long Baseline Array observations, finding no significant extended, jet-like features down to $\sim$1 pc scales. The flat spectral index ($α_{1.6}^{8.4} = 0.03$) high brightness temperature ($T_{\rm b} \sim...
We have made measurements to determine the parallax and proper motion of three 6.7-GHz methanol masers G305.200$+$0.019, G305.202$+$0.208 G305.208$+$0.206. The combined is found be 0.25$\pm $0.05 mas, corresponding a distance 4.1$^{+1.2}_{-0.7}$ kpc. This places G305.2 star formation region in Carina-Sagittarius spiral arm. inclusion increases Galactic azimuth range sources this arm by 40$^\circ $ from Sato et al., allowing us pitch angle with greater confidence $\psi = 19.0 \pm 2.6^\circ $....
We use data on extreme radio scintillation to demonstrate that this phenomenon is associated with hot stars in the solar neighbourhood. The ionized gas responsible for scattering found at distances up 1.75pc from host star, and average must comprise 1.E5 distinct structures per star. detect azimuthal velocities of plasma, relative 9.7 km/s, consistent warm expanding sound speed. circumstellar plasma we infer are similar several respects cometary knots seen Helix, other planetary nebulae....
Adding VLBI capability to the SKA arrays will greatly broaden science of SKA, and is feasible within current specifications.SKA-VLBI can be initially implemented by providing phased-array outputs for SKA1-MID SKA1-SUR using these extremely sensitive stations with other radio telescopes, in SKA2 realising a distributed configuration baselines up thousands km, merging it existing networks.The motivation possible realization SKA-VLBI described this paper.
The AUSTRAL observing program was started in 2011, performing geodetic and astrometric very long baseline interferometry (VLBI) sessions using the new Australian AuScope VLBI antennas at Hobart, Katherine, Yarragadee, with contribution from Warkworth (New Zealand) 12 m Hartebeesthoek (South Africa) 15 to make a southern hemisphere array of telescopes similar design capability. Designed style next-generation system, these small fast allow for way observing, comprising higher data rates more...
We report the first observation of nearby giant radio galaxy NGC 315 using a global VLBI array consisting 22 antennas located across five continents, including high-sensitivity stations, at GHz. Utilizing extensive $(u,v)$-coverage provided by array, coupled with application recently developed super-resolution imaging technique based on regularized maximum likelihood method, we were able to transversely resolve jet parsec scales for time. Previously known its central ridge-brightened...
We present the highest resolution, wide-field radio survey of a nearby face-on star-forming galaxy to date. The multiphase centre technique is used entire disc M51 (77 arcmin2) at maximum resolution 5 mas on single 8 h pointing with European Very Long Baseline Interferometry (VLBI) Network 18 cm. In total, 7 billion pixels were imaged using 192 phase centres that resulted in detection six sources: Seyfert nucleus, supernova SN 2011dh, and four background AGNs. Using wealth archival data...
Compact radio sources sometimes exhibit intervals of large, rapid changes in their flux-density, due to lensing by interstellar plasma crossing the line-of-sight. A novel survey program has made it possible discover these "Extreme Scattering Events" (ESEs) real time, resulting a high-quality dynamic spectrum an ESE observed PKS 1939-315. Here we present method for determining column-density profile lens, given only lensed source, under assumption that lens is either axisymmetric or totally...