The Square Kilometre Array (SKA): publications

Searching for substellar companions of young isolated neutron stars*

Astronomy & Astrophysics EDP Sciences 496:2 (2009) 533-545

Authors:

B Posselt, R Neuhäuser, F Haberl

Future investigations of GPS and CSS radio sources with LOFAR

Astronomische Nachrichten 330 (2009) 297-297

Authors:

IAG Snellen, HJA Röttgering, PD Barthel, PN Best, M Brüggen, JE Conway, MJ Jarvis, MD Lehnert, GK Miley, R Morganti

The complex polarization angles of radio pulsars: orthogonal jumps and interstellar scattering

ArXiv 0901.1826 (2009)

Abstract:

Despite some success in explaining the observed polarisation angle swing of radio pulsars within the geometric rotating vector model, many deviations from the expected S-like swing are observed. In this paper we provide a simple and credible explanation of these variations based on a combination of the rotating vector model, intrinsic orthogonally polarized propagation modes within the pulsar magnetosphere and the effects of interstellar scattering. We use simulations to explore the range of phenomena that may arise from this combination, and briefly discuss the possibilities of determining the parameters of scattering in an effort to understand the intrinsic pulsar polarization.

A digital broadband beamforming architecture for 2-PAD

Proceedings of Science 132 (2009) 273-277

Authors:

R Armstrong, J Hickish, KZ Adami, ME Jones

Abstract:

The development of densely-packed, all-digital aperture arrays is an important area of research required for the Square Kilometre Array (SKA) radio telescope. The design of real-time signal processing systems for digital aperture arrays is currently a central challenge in pathfinder projects worldwide. We describe an hierarchical, frequency-domain beamforming architecture for synthesising a sky beam from the wideband antenna feeds of digital aperture arrays. In particular this work describes a specific implementation of the beamforming architecture to the 2-Polarisation All-Digital (2-PAD) aperture array demonstrator.

AMI observations of northern supernova remnants at 14-18 GHz

Monthly Notices of the Royal Astronomical Society 396:1 (2009) 365-376

Authors:

N Hurley-Walker, AMM Scaife, DA Green, ML Davies, K Grainge, MP Hobson, ME Jones, T Kaneko, A Lasenby, G Pooley, RDE Saunders, PF Scott, D Titterington, E Waldram, JTL Zwart

Abstract:

We present observations between 14.2 and 17.9 GHz of 12 reported supernova remnants (SNRs) made with the Arcminute Microkelvin Imager Small Array (AMI SA). In conjunction with data from the literature at lower radio frequencies, we determine spectra of these objects. For well-studied SNRs (Cas A, Tycho's SNR, 3C 58 and the Crab Nebula), the results are in good agreement with spectra based on previous results. For the less well-studied remnants, the AMI SA observations provide higher-frequency radio observations than previously available, and better constrain their radio spectra. The AMI SA results confirm a spectral turnover at ≃11 GHz for the filled-centre remnant G74.9+1.2. We also see a possible steepening of the spectrum of the filled-centre remnant G54.1+0.3 within the AMI SA frequency band compared with lower frequencies. We confirm that G84.9+0.5, which had previously been identified as a SNR, is rather an H ii region and has a flat radio spectrum. © 2009 RAS.

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