Journal Article

Dynamic emission properties of pulsars B0943+10 and B1822–09 – I. Comparison, and the discovery of a ‘Q’-mode precursor

Isaac Backus, Dipanjan Mitra and Joanna M. Rankin

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 404, issue 1, pages 30-41
Published in print May 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2009.16102.x
Dynamic emission properties of pulsars B0943+10 and B1822–09 – I. Comparison, and the discovery of a ‘Q’-mode precursor

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This paper reports new observations of pulsars B0943+10 and B1822−09 carried out with the Arecibo Observatory and the Giant Metrewave Radio Telescope, respectively. Both stars exhibit two stable emission modes. We report the discovery in B0943+10 of a highly linearly polarized ‘precursor’ (PC) component that occurs primarily in only one mode. This emission feature closely resembles B1822−09's PC which also occurs brightly in only one mode. B0943+10's other mode is well known for its highly regular drifting subpulses that are apparently produced by a rotating ‘carousel’ system of 20 ‘beamlets.’ Similarly, B1822−09 exhibits subpulse-modulation behaviour only in the mode where its PC is absent. We survey our 18 h of B0943+10 observations and find that the ‘sideband’-modulation features, from which the carousel-rotation time can be directly determined, occur rarely – less than 5 per cent of the time – but always indicating 20 ‘beamlets’. We present an analysis of B1822−09's modal modulation characteristics at 325 MHz and compare them in detail with B0943+10. The pulsar never seems to null, and we find a 43-rotation-period P3 feature in the star's ‘Q’ mode that modulates the interpulse (IP) as well as the conal features in the main pulse (MP). We conclude that B1822−09 must have a nearly orthogonal geometry and that its carousel circulation time is long compared to the modal subsequences available in our observations, and the MP/IP separation is almost exactly 180°. We conclude the PCs for both stars are incompatible with core–cone emission. We assess the interesting suggestion by Dyks et al. that downward-going radiation produces B1822−09's PC emission.

Keywords: MHD; plasmas; polarization; pulsars: general; pulsars: individual: B0943+10; pulsars: individual: B1822−09

Journal Article.  9041 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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