A5107984535- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Neutrino Physics Research
- Geophysics and Gravity Measurements
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Particle Accelerators and Free-Electron Lasers
- Magnetic confinement fusion research
- Astronomy and Astrophysical Research
- GNSS positioning and interference
- Mechanics and Biomechanics Studies
- Atomic and Subatomic Physics Research
- Gyrotron and Vacuum Electronics Research
- International Science and Diplomacy
- Advanced Measurement and Metrology Techniques
- Ionosphere and magnetosphere dynamics
- Radio Wave Propagation Studies
- Cosmology and Gravitation Theories
- Adaptive optics and wavefront sensing
- Advanced Frequency and Time Standards
University of Tasmania
2009-2023
National Radio Astronomy Observatory
2019-2023
New Mexico Institute of Mining and Technology
2023
Joint Institute for VLBI ERIC
2017-2020
University of Concepción
2013-2020
Arizona Optical Systems (United States)
2019
Australia Telescope National Facility
2011
Commonwealth Scientific and Industrial Research Organisation
2011
Astronomy and Space
2011
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...
Centaurus A is the closest radio-loud active galaxy. Very Long Baseline Interferometry (VLBI) enables us to study jet-counterjet system on milliarcsecond (mas) scales, providing essential information for jet emission and propagation models. We evolution of central parsec structure Cen over 3.5 years. The proper motion analysis individual components allows constrain formation test proposed correlation increased high energy flux with ejection events. an exceptional laboratory such detailed as...
The Fermi Gamma-Ray Space Telescope has been detecting a wealth of sources where the multiwavelength counterpart is either inconclusive or missing altogether. We present combination factors that can be used to identify counterparts these unassociated sources. This approach was select and investigate seven bright, high-latitude with radio, UV, X-ray, γ-ray observations. As result, four are candidates active galactic nuclei, one pulsar, while two do not fit easily into known categories latter...
The IceCube Collaboration has announced the discovery of a neutrino flux in excess atmospheric background. Owing to steeply falling background spectrum, events at PeV energies most likely have an extraterrestrial origin. We present multiwavelength properties six radio-brightest blazars that are positionally coincident with these using contemporaneous data TANAMI blazar sample, including high-resolution images and spectral energy distributions. Assuming X-ray γ-ray emission originates...
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...
We investigate the nature and classification of PMNJ1603-4904, a bright radio source close to Galactic plane, which is associated with one brightest hard-spectrum gamma-ray sources detected by Fermi/LAT. It has previously been classified as low-peaked BL Lac object based on its broadband emission absence optical lines. Optical measurements, however, suffer strongly from extinction pronounced short-time variability over years monitoring unusual for blazar. are combining new archival...
Context. Simultaneous broadband spectral and temporal studies of blazars are an important tool for investigating active galactic nuclei (AGN) jet physics.
PKS2142-75 (a.k.a. 2FGL J2147.4-7534) is a flat-spectrum radio quasar that was observed quasi-simultaneously by suite of instruments across the elec- tromagnetic spectrum during two flaring states in April 2010 and August 2011 as well quiescent state December through January 2012. The results these campaigns model spectral energy distributions (SEDs) from active are presented. SED parameters PKS 2142-75 indicate flares source created unique physical conditions. studies flat quasars beginning...
Using high-resolution radio imaging with VLBI techniques, the TANAMI program has been observing parsec-scale jets of southern (declination south -30{\deg}) gamma-ray bright AGN simultaneously Fermi/LAT monitoring their emission. We present and properties sources based on one year contemporaneous data. A large fraction (72%) sample can be associated for this time range. Association rates differ different optical classes all BL Lacs, 76% quasars just 17% galaxies detected by LAT. Upper limits...
We present new Karl G. Jansky Very Large Array (JVLA) and Long Baseline (VLBA) observations that traced the H I in central region of 3C 84 (Perseus A). This radio source is hosted by bright cluster galaxy NGC 1275 centre iconic Perseus cluster. With JVLA, we detected very broad (FWHM ∼500 km s −1 ) absorption at arcsecond resolution (∼300 pc) centred systemic velocity against continuum, suggesting gas close to supermassive black hole (SMBH). However, did not detect any higher-resolution VLBA...
This paper reports observations of a 22 GHz water maser `superburst' in the G25.65+1.05 massive star forming region, conducted response to an alert from Maser Monitoring Organisation (M2O). Very long baseline interferometry (VLBI) using European VLBI Network (EVN) recorded flux density $1.2 \times 10^{4}$ Jy. The superburst was investigated spectral, structural and temporal domains its cause determined be increase path length generated by superposition multiple emitting regions aligning line...
We have studied the archetypal Gigahertz Peaked Spectrum radio galaxy, PKS 1934 − 638, using Australian Long Baseline Array augmented with two new telescopes that greatly improve angular resolution of array. These very long baseline interferometry observations represent first scientific results from a antenna in New Zealand and SKA Pathfinder. A compact double source, 638 has been monitored over period 40 years observation described here provides latest datum, eight after previous...
The binary system AR Sco contains an M star and the only known radio-pulsing white dwarf. shows emission from radio to X-rays, likely dominated by synchrotron radiation. mechanism that produces most of this remains unclear. Two competing scenarios have been proposed: Collimated outflows, direct interaction between magnetospheres dwarf star. two proposed can be tested via very long baseline interferometric observations. We conducted a observation with Australian Long Baseline Array (LBA) on...
The flat spectrum radio quasar (FSRQ) PKS 2123-463 was associated in the First Fermi-LAT source catalog with gamma-ray 1FGL J2126.1-4603, but when considering full first two years of Fermi observations, no at a position consistent this FSRQ detected, and thus not reported Second catalog. On 2011 December 14 positionally detected flaring activity by Fermi-LAT. This triggered radio-to-X-ray observations Swift, GROND, ATCA, Ceduna, KAT-7 observatories. Results localization over 41 months...
Rapid variability in the radio flux density of BL Lac object PKS B1144−379 has been observed at four frequencies, ranging from 1.5 to 15 GHz, with Very Large Array and University Tasmania's Ceduna antenna. Intrinsic line-of-sight effects were examined as possible causes this variability, interstellar scintillation best explaining frequency dependence timescales modulation indices. This is consistent a compact source 20–40 μas or 0.15–0.3 pc size. The inferred brightness temperature for...
Context. Blazars are a subset of active galactic nuclei (AGN) with jets that oriented along our line sight. Variability and spectral energy distribution (SED) studies crucial tools for understanding the physical processes responsible observed AGN emission. Aims. We report peculiar behaviour in bright gamma-ray blazar PKS 1424-418 use its strong variability to reveal information about particle acceleration interactions jet. Methods. Correlation analysis extensive optical coverage by ATOM...
Centaurus A (Cen A) is a bright radio source associated with the nearby galaxy NGC 5128 where high-resolution observations can probe jet at scales of less than light-day. The South Pole Telescope (SPT) and Atacama Pathfinder Experiment (APEX) performed single-baseline very-long-baseline interferometry (VLBI) observation Cen in January 2015 as part VLBI receiver deployment for SPT. We measure correlated flux density wavelength 1.4 mm on $\sim$7000 km (5 G$\lambda$) baseline. Ascribing this to...
TANAMI is a multiwavelength program monitoring active galactic nuclei (AGN) south of -30deg declination including high-resolution Very Long Baseline Interferometry (VLBI) imaging, radio, optical/UV, X-ray and gamma-ray studies. We have previously published first-epoch 8.4GHz VLBI images the parsec-scale structure initial sample. In this paper, we present 39 additional sources. The full sample comprises most radio- brightest AGN in southern quarter sky, overlapping with region from which...
Context. Frequent, simultaneous observations across the electromagnetic spectrum are essential to study of a range astrophysical phenomena including Active Galactic Nuclei. A key tool such studies is ability observe an object when it flares i.e. exhibits rapid and significant increase in its flux density. Aims. We describe specific observational procedures calibration techniques that have been developed tested create single baseline radio interferometer can rapidly flaring object. This only...
Abstract The rapid variability of X-ray binaries (XRBs) produces a wide range states that are linked to activity across the electromagnetic spectrum. It is particularly challenging study sample sources large enough include all types in their various states, and cover full frequencies show flux density variations. Simultaneous observations with many telescopes necessary. In this project, we monitor 48 XRBs seven spectrum from 5 × 10 9 19 Hz, including ground-based radio, IR, optical...