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Modal sequencing and dynamic emission properties of an 8-h Giant Metrewave Radio Telescope observation of pulsar B1822−09

Authors

  • Crystal Latham,

    Corresponding author
    • Physics Department, University of Vermont, Burlington, VT, USA
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  • Dipanjan Mitra,

    Corresponding author
    1. National Centre for Radio Astrophysics, Ganeshkhind, Pune, India
    • Physics Department, University of Vermont, Burlington, VT, USA
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  • Joanna Rankin

    Corresponding author
    1. Sterrenkundig Instituut ‘Anton Pannekoek’, University of Amsterdam, GE Amsterdam, the Netherlands
    • Physics Department, University of Vermont, Burlington, VT, USA
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E-mail: crystal.latham@uvm.edu (CL); dmitra@ncra.tifr.res.in (DM); joanna.rankin@uvm.edu (JR)

ABSTRACT

The research presented here examines an 8-h observation of pulsar B1822−09, taken by the Giant Metrewave Radio Telescope. B1822−09 has been known to exhibit two stable emission modes, the B-mode, where the precursor (PC) ‘turns-on’, and the Q-mode, which is defined by interpulse (IP) emission. The results of our analysis, of this extremely long observation, have shown that B1822−09 exhibits at least three other emission behaviours that have not been seen before in other similar pulsars or in other observations of B1822−09. These three behaviours can be described as Q-mode emission with PC emission, B-mode emission with IP emission and instances where both the PC and IP are ‘on’ when transitioning from one mode to the other. The pulse structure has been found to be more complex than previously thought. The main pulse (MP) has an inner cone/core triple (T) configuration together with a central sightline traverse. The IP is a 15°-wide region that along with the MP originate from an open dipolar field. The PC emission comes from a still unknown source. We argue that the PC emission arises within the same region as the MP, but likely comes from higher in the magnetosphere. The Q-mode has a very clear fluctuation that occurs in both the MP and IP at 46.6-P1 which is associated with drifting subpulses. Furthermore, we have found that the B-mode, which has previously never shown any detectable modulations at this radio frequency, has a very weak feature at 70-P1. Coincidently we find the ratio of the B-mode ‘P3’ of 70-P1 to its Q-mode counterpart of 46.6-P1 is very nearly 3/2, which seems to imply a carousel of three MP ‘sparks’ in the Q-mode and two sparks in the B-mode. The circulation times of the two modes have been found to be virtually equal at 140-P1, which allows for this interpretation of the fluctuation features as ‘sparks’. Overall, our analyses strongly suggest that mode changes allow information transfer between the two magnetic polar regions and contribute to global magnetospheric changes.

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