A5045145820- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Magnetic confinement fusion research
- Geophysics and Gravity Measurements
- Superconducting Materials and Applications
- Geomagnetism and Paleomagnetism Studies
- Atomic and Molecular Physics
- Ionosphere and magnetosphere dynamics
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Particle Accelerators and Free-Electron Lasers
- Radio Astronomy Observations and Technology
- Dark Matter and Cosmic Phenomena
- Characterization and Applications of Magnetic Nanoparticles
- Geological and Geochemical Analysis
- Particle accelerators and beam dynamics
- Earthquake Detection and Analysis
Australian National University
2016-2025
Australian Mathematical Sciences Institute
2016-2025
La Trobe University
2020-2024
Macquarie University
2020-2024
Kinokuniya
2020-2024
Monash University
2010-2024
Marymount University
2020-2024
Curtin University
2019-2023
International Centre for Radio Astronomy Research
2019-2023
The University of Queensland
2021-2022
The MiMeS (Magnetism in Massive Stars) project is a large-scale, high-resolution, sensitive spectropolarimetric investigation of the magnetic properties O- and early B-type stars. Initiated 2008 completed 2013, was supported by three Large Program allocations, as well various programmes initiated independent principal investigators, archival resources. Ultimately, over 4800 circularly polarized spectra 560 O B stars were collected with instruments ESPaDOnS (Echelle SpectroPolarimetric Device...
Since the discovery of first isolated magnetic white dwarf (MWD) Grw +70°8047 nearly 60 years ago, number stars belonging to this class has grown steadily. There are now some 65 dwarfs classified as magnetic, and a roughly equal MWDs found in close interacting binaries known cataclysmic variables (MCVs). The comprise ∼5% all WDs, while MCVs ∼25% CVs. fields range from ∼ 3 × 104–109 G former group with distribution peaking at 1.6 107 G, 107–3 108 latter group. space density is estimated be...
We study the statistics of 61 measured masses neutron stars (NSs) in binary pulsar systems, including 18 double NS (DNS) 26 radio pulsars (10 our Galaxy) with white dwarf (WD) companions, 3 NSs main-sequence 13 X-ray binaries, and one undetermined system. derive a mean value M = 1.46 ± 0.30 M⊙. When 46 spin periods are divided into two groups at 20 milliseconds, i.e., millisecond (MSP) group others, we find that their mass averages are, respectively, 1.57 0.35 M⊙ 1.37 0.23 In framework...
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...
White dwarfs with surface magnetic fields in excess of $1 $MG are found as isolated single stars and relatively more often cataclysmic variables. Some 1,253 white a detached low-mass main-sequence companion identified the Sloan Digital Sky Survey but none these is observed to show evidence for Zeeman splitting hydrogen lines associated field 1MG. If such high on result from evolution star then there should be same fraction among this SDSS binary sample stars. Thus we deduce that origin must...
Abstract We consider the incidence of magnetism in main-sequence stars with mainly radiative envelopes. propose that small fraction, which increases mass, are magnetic can be explained if towards end formation process, after have developed a substantial envelope, correspondingly fraction merge. Such late mergers would produce brief period strong differential rotation and give rise to large-scale fields also account for lack close binaries among these stars.
We explore the hypothesis that magnetic fields of neutron stars are fossil origin. For parametrised models distribution flux on Main Sequence and birth spin period stars, we calculate expected properties isolated radio pulsars in Galaxy using as our starting point initial mass function star formation rate a galacto-centric radius. then use 1374 MHz Parkes Multi-Beam Survey to constrain parameters model deduce required main sequence. find agreement with observations for corresponds supernova...
Observations of magnetic A, B and O stars show that the poloidal flux per unit mass Φp/M appears to have an upper bound approximately 10−6.5 G cm2 g−1. A similar total is found for white dwarfs even though highest field strengths at their surfaces are much larger. For stars, there also be a well-defined lower below which incidence magnetism declines rapidly. According recent hypotheses, both groups may result from merging owe strong fields generated by dynamo mechanism as they merge. We...
Subluminous Type Ia supernovae, such as the Iax class prototype SN 2002cx, are described by a variety of models failed detonation and partial deflagration an accreting carbon-oxygen white dwarf star, or explosion accreting, hybrid carbon-oxygen-neon core. These predict that bound remnants survive events with, according to some simulations, high kick velocity. We report discovery proper motion, low-mass (LP 40-365) travels at velocity greater than Galactic escape whose peculiar atmosphere is...
We investigate evolutionary pathways leading to neutron star formation through the collapse of oxygen-neon white dwarf (ONe WD) stars in interacting binaries. consider (1) non-dynamical mass transfer where an ONe WD approaches Chandrasekhar accretion-induced (AIC) and (2) dynamical timescale merger-induced (MIC) between another WD. present rates, delay times, progenitor properties for two different treatments common envelope evolution. show that AIC are formed via many channels most dominant...
Spectropolarimetric observations of the extreme-ultraviolet (EUV) source and high-field magnetic white dwarf EUVE J0317—855 ( = RE J0317—853) in wavelength range 4200–7200 Å reveal a strongly structured circular polarization spectrum with peak 8 per cent. The strongest features are attributed to Hα 2s0-3p1, 2s0-3p0 Hβ 2s0-4f-1, 2s0-4f0 2s0-4p1 field 100–300 MG. phase-averaged data modelled using centred off-centred dipole structures, reasonable fit was obtained for strength Bd 450 MG...
Magnetic white dwarfs with fields in excess of ∼106 G (the high field magnetic dwarfs; HFMWDs) constitute about ∼10 per cent all and show a mass distribution mean ∼0.93 M⊙ compared to ∼0.56 for dwarfs. We investigate two possible explanations these observations. First, that the initial–final relationship (IFMR) is influenced by presence observed HFMWDs originate from stars on main sequence are recognized as chemically peculiar A B stars). Secondly, IFMR essentially unaffected field, have...
Recent studies of white dwarfs in open clusters have provided new constraints on the initial—final mass relationship (IFMR) for main-sequence stars with masses range 2.5–6.5 M⊙. We re-evaluate ensemble data that determines IFMR and argue can be characterized by a mean about which there is an intrinsic scatter. investigate consequences observed distribution field using population synthesis calculations. show while linear predicts reasonable agreement recent results from Palomar—Green survey,...
A magnetic dynamo driven by differential rotation generated when stars merge can explain strong fields in certain classes of stars, including the high field white dwarfs (HFMWDs). In their case site has been variously proposed to be within a common envelope, massive hot outer regions merged degenerate core or an accretion disc formed tidally disrupted companion that is subsequently incorporated into core. We synthesize population binary systems investigate stellar merging hypothesis for...
Recent spectropolarimetric observations of Ap and Bp stars with improved sensitivity have suggested that most are magnetic dipolar fields at least a few hundred gauss. These new estimates suggest the range fluxes found for majority white dwarfs is similar to main-sequence Ap–Bp stars, thus strengthening empirical evidence an evolutionary link between magnetism on main sequence in dwarfs. We draw parallels neutron argue observed isolated (Bp∼ 1011–1015 G) could also be explained if their...
The Sloan Digital Sky Survey has already more than doubled the sample of white dwarfs with spectral classifications, subset detached M dwarf companions, and magnetic dwarfs. In course assessing these new discoveries, we have noticed a curious, unexpected property total lists plus main-sequence binaries: there appears to be virtually zero overlap between two samples! No confirmed yet been found in such pairing star. same statement can made for samples dwarf–M pairs wide, common proper motion...
It has generally been assumed that neutron stars (NSs) become millisecond pulsars (MSPs) originated in a core–collapse supernova. The possibility of formation by accretion-induced collapse (AIC) an oxygen/neon white dwarf (WD) largely ignored or considered negligible. Here, we demonstrate population synthesis calculations with generic assumptions yield birthrates binary MSPs via AIC are comparable to and can exceed those for core collapse. Allowing both modes NS formation, estimate orbital...
We report the discovery of a new, polluted, magnetic white dwarf in Luyten survey high-proper motion stars. High-dispersion spectra NLTT 7547 reveal complex heavy element line spectrum cool (~5 200 K) hydrogen-dominated atmosphere showing effect surface averaged field 163 kG, consistent with 240 kG centred dipole, although actual structure remains uncertain. The abundance pattern shows accreted material distinct magnesium-rich flavour. Combined earlier identifications, this supports...
ABSTRACT We have investigated the origin of a sub-class carbon-polluted white dwarfs (DQ) originally identified as “hot DQ” dwarfs. These objects are relatively hot ($10\, 000\lesssim T_{\rm eff}\lesssim 25\, 000$ K), markedly higher carbon abundance (C-enriched), more massive (M ≳ 0.8 M⊙) than ordinary DQs ∼ 0.6 M⊙), and display high space velocities. Hence, despite their young appearance kinematic properties those an old dwarf population. The way out this dilemma is to assume that they...
Observations of main-sequence stars conducted over the last several decades have clearly shown that something like 50 per cent spectral types G and F occur in multiple systems. For earlier types, incidence multiplicity is even higher. Thus, a volume-limited sample white dwarfs should reflect percentage binarity observed to late B which are their progenitors. However, study local (20 pc from Sun) by Holberg has dwarf probability only ∼32 occurring binary system, stark contrast observations...