Browsing School of Physics by Author "Shearer, Andrew"
Now showing items 1-18 of 18
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Circular polarization of synchrotron radiation in high magnetic fields
de Burca, Diarmaid; Shearer, Andrew (Oxford University Press, 2015-04-17)The general model for incoherent synchrotron radiation has long been known, with the first theory being published by Westfold in 1959 and continued by Westfold and Legg in 1968. When this model was first developed, it was ... -
Dark spot, Spiral waves and the SW Sex behaviour: it is all about UX Ursae Majoris
Shearer, Andrew (2010)We present an analysis of time-resolved, medium resolution optical spectroscopic observations of UX UMa in the blue (3920-5250 A) and red (6100-7200 A) wavelength ranges, that were obtained in April 1999 and March 2008 ... -
Discovery of a faint X-ray counterpart and of a parsec-long X-ray tail for the middle-aged, gamma-ray only pulsar PSR J0357+3205
Shearer, Andrew (2011)The Large Area Telescope (LAT) onboard the Fermi satellite opened a new era for pulsar astronomy, detecting gamma-ray pulsations from more than 60 pulsars, ~40% of which are not seen at radio wavelengths. One of the most ... -
Electron beam therapy at extended SSD: a Monte Carlo investigation of output fom a Siemens Oncor linear accelerator
Foley, Mark J.; O'Shea, T. P.; Downes, Patrick A.; Shearer, Andrew (2008)Electron-beam therapy is used to treat superficial tumors at a standard 100 cm source-to-surface distance (SSD). However, certain clinical situations require the use of an extended SSD. In the present study, Monte Carlo ... -
The Galway astronomical Stokes polarimeter: an all-Stokes optical polarimeter with ultra-high time resolution
Collins, Patrick; Kyne, Gillian; Lara, David; Redfern, Michael; Shearer, Andrew; Sheehan, Brendan (Springer Verlag, 2013-06-28)Many astronomical objects emit polarised light, which can give information both about their source mechanisms, and about (scattering) geometry in their source regions. To date (mostly) only the linearly polarised components ... -
GASP - Galway Astronomical Stokes Polarimeter
Shearer, Andrew (2009)The Galway Astronomical Stokes Polarimeter (GASP) is an ultra-high-speed, full Stokes, astronomical imaging polarimeter based upon a Division of Amplitude Polarimeter. It has been developed to resolve extremely rapid ... -
High Time Resolution Astrophysics in the Extremely Large Telescope Era : White Paper
Shearer, Andrew (2010)High Time Resolution Astrophysics (HTRA) concerns itself with observations on short scales normally defined as being lower than the conventional read-out time of a CCD. As such it is concerned with condensed objects such ... -
High-time Resolution Astrophysics and Pulsars
Shearer, Andrew (2008)The discovery of pulsars in 1968 heralded an era where the temporal characteristics of detectors had to be reassessed. Up to this point detector integration times would normally be measured in minutes rather seconds and ... -
An investigation of the Eigenvalue Calibration Method (ECM) using GASP for non-imaging and imaging detectors
Kyne, Gillian; Lara, David; Hallinan, Gregg; Redfern, Michael; Shearer, Andrew (Springer Verlag, 2016-02)Polarised light from astronomical targets can yield a wealth of information about their source radiation mechanisms, and about the geometry of the scattered light regions. Optical observations, of both the linear and ... -
Investigations of the magnetospheric plasma distribution in the vicinity of a pulsar - I Basic formulation
Shearer, Andrew (2008)The magnetospheric plasma distribution in the vicinity of a pulsar at various inclination angles is investigated using a new relativistic, parallel 3D Particle-In-Cell (PIC) code DYMPHNA3D. DYMPHNA3D uses a superposition ... -
Kinematics of the Broad Line Region in M81
Shearer, Andrew (2007)A new model is presented which explains the origin of the broad emission lines observed in the LINER/Seyfert nucleus of M81 in terms of a steady state spherically symmetric inflow, amounting to 1 x 10^-5 Msun/yr, which is ... -
Optical Observations of PSR J0205+6449
Shearer, Andrew (2008)PSR J0205+6449 is a X-ray and radio pulsar in supernova remnant 3C 58. We report on observations of the central region of 3C 58 using the 4.2-m William Herschel Telescope with the intention of identifying the optical ... -
Optical pulsations from the anomalous X-ray pulsar 1E 1048.1-5937
Shearer, Andrew (2009)We present high-speed optical photometry of the anomalous X-ray pulsar 1E 1048.1-5937 obtained with ULTRACAM on the 8.2-m Very Large Telescope in June 2007. We detect 1E 1048.1-5937 at a magnitude of i'=25.3+/-0.2, consistent ... -
Pulse variation of the optical emission of Crab pulsar
Shearer, Andrew (2007)The stability of the optical pulse of the Crab pulsar is analyzed based on the 1 $\mu$s resolution observations with the Russian 6-meter and William Hershel telescopes equipped with different photon-counting detectors. The ... -
A recent change in the optical and gamma ray polarization of the Crab nebula and pulsar
Moran, Paul; Kyne, Gillian; Redfern, R. M.; Shearer, Andrew (Oxford journals, 2015-12-31)We report on observations of the polarization of optical and γ-ray photons from the Crab nebula and pulsar system using the Galway Astronomical Stokes Polarimeter (GASP), the Hubble Space Telescope, Advanced Camera for ... -
A search for optical bursts from RRAT J1819-1458: II. Simultaneous ULTRACAM-Lovell Telescope observations
Shearer, Andrew (2011)The Rotating RAdio Transient (RRAT) J1819-1458 exhibits ~3 ms bursts in the radio every ~3 min, implying that it is visible for only ~1 per day. Assuming that the optical light behaves in a similar manner, long exposures ... -
The study of neutron star magnetospheres with LOFT
Shearer, Andrew (2015)The Large Observatory for X-ray Timing, LOFT, is designed to perform fast X-ray timing and spectroscopy with uniquely large throughput (Feroci et al. 2014). LOFT focuses on two fundamental questions of ESA’s Cosmic Vision ... -
VLT polarimetry observations of the middle-aged pulsar PSR B0656+14
Moran, Paul; Shearer, Andrew (EDP Sciences, 2015-11-02)Context. Optical polarisation measurements are key tests for different models of the pulsar magnetosphere. Furthermore, comparing the relative orientation of the phase-averaged linear polarisation direction and the pulsar ...