A5052077765- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- High-pressure geophysics and materials
- Magnetic confinement fusion research
- Geophysics and Gravity Measurements
- Superconducting Materials and Applications
- Geomagnetism and Paleomagnetism Studies
- Mechanics and Biomechanics Studies
- Space Science and Extraterrestrial Life
- Spectroscopy and Laser Applications
- Adaptive optics and wavefront sensing
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Atmospheric Ozone and Climate
- Ionosphere and magnetosphere dynamics
- Molecular Spectroscopy and Structure
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
Australian National University
2014-2024
Australian Mathematical Sciences Institute
2013-2024
University of Ruhuna
2018-2021
Institute of Astronomy
1971-2010
University of Arizona
1991-2010
Monash University
2007-2010
Infusion (South Africa)
2004
University of Illinois Urbana-Champaign
2002
Royal Observatory
1979-2000
Australia and New Zealand Melanoma Trials Group
1999
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...
view Abstract Citations (332) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Asteroseismology of the DOV Star PG 1159-035 with Whole Earth Telescope Winget, D. E. ; Nather, R. Clemens, J. C. Provencal, Kleinman, S. Bradley, P. A. Wood, M. Claver, F. Frueh, L. Grauer, Hine, B. Hansen, Fontaine, G. Achilleos, N. Wickramasinghe, T. Marar, K. Seetha, Ashoka, O'Donoghue, Warner, Kurtz, W. Buckley, Brickhill, Vauclair, Dolez, Chevreton, Barstow,...
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...
We have conducted a survey of 61 southern white dwarfs searching for magnetic fields using Zeeman spectropolarimetry. Our objective is to obtain field distribution these objects and, in particular, find with weak fields. found one possible candidate (WD 0310-688) that may -6.1+/-2.2 kG. Next, we determine the fraction and Solar neighborhood, investigate probability finding more based on current incidence magnetism within 20 pc Sun. also analyzed spectra effective temperatures surface gravities.
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...
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...
The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations pulsating dwarfs, we can measure their internal structures compositions, critical to understanding post main sequence evolution, along with cooling rates, allowing us calibrate ages directly. most important set dwarf variables oldest pulsators, cool DAVs, which have not previously been explored through asteroseismology due complexity instability. a time-series photometry...
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...
A propagation algorithm based on finite elements and a difference discretisation of the scalar wave equation is investigated as an alternative to beam method. The new approach overcomes assumption low contrast media in BPM allows arbitrary input fields strongly guiding structures.
We present calculations of cyclotron and free–free emission for a wide range values the electron temperature (Te), frequency (ω/ωc), viewing angle with respect to magnetic field (θ) size parameter (Λ) both constant models incorporating structure (shock front models). It is argued that observed optical properties AM Herculis-type systems are inconsistent low-temperature (Te<5 keV) regions but in general agreement predictions from high-temperature models. The low Λ deduced same order magnitude...
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...
AM Her variables – synchronized magnetic cataclysmic (CVs) exhibit a different period distribution from other CVs across the gap. We show that non-AM systems may infiltrate longer-period end of gap if they are metal-deficient, but position and width in orbital otherwise insensitive to binary parameters (except for normalization braking rate). In binaries, is reduced as wind secondary star be trapped within magnetosphere white dwarf primary. This fills its short-period dipole moment...
We present calculations of the intensity and polarization cyclotron radiation from constant temperature magnetic accretion columns. The results are in agreement with general observed properties AM Herculis type systems. linear pulse is caused primarily by Faraday mixing characteristic high harmonic number (n ≳ 5). rate change position angle during gives a direct measure between line sight rotation axis white dwarf for synchronous orbit. predicted continuum energy distributions due to have...
Circinus X-l (3U 1516 – 56) has a radio counterpart which, at high frequencies, shows flares with the same 16.6-day periodicity as X-ray intensity. In each cycle flare occurs shortly after intensity drop-off which defines modulation.