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21-08-2025
Summer project: investigating the mode changing behaviour of PSR J0904-4246
| Submitter: | Marta Cholewa |
| Description: | The single-pulse emission of pulsars exhibits a variety of behaviours, including drifting, nulling, and mode-switching. These phenomena probe the changes in the pulsar magnetosphere. However, many cannot be fully explained by simple emission models. Pulsar J0904-4246 exhibits mode-switching, whose emission pattern changes between two distinct modes. It has been monitored over five years using the highly sensitive MeerKAT telescope as part of the Thousand-Pulsar-Array (TPA) programme. From the collected about 13,000 single pulses, each pulse was classified as belonging to either the Weak or Bright mode, based on its intensity profile (middle panels). The Weak mode exhibits a double-peaked average profile with a stronger leading component (top left panel), whereas the Bright mode shows a triple-peaked profile dominated by the central component (top right panel). The modes differ not only in their average profile shapes and intensities but also in their polarimetric properties. By calculating the position angle (PA) of linear polarisation for individual pulses and constructing histograms, these differences are clearly seen (bottom two panels). Both modes show the characteristic S-shaped PA swing predicted by the rotating vector model, indicating that the underlying emission geometry is stable. However, the Bright mode additionally presents an orthogonal polarisation mode, 90 degrees offset from the usual S-shaped PA track (bottom right panel). The physical origin of OPMs is not fully understood, and it remains unclear why some pulsars exhibit this phenomenon. Beyond mode-switching, PSR J0904-4246 shows even more interesting behaviours, like drifting patterns and intensity periodicity in the Weak mode. These phenomena provide valuable insight into the structure and dynamics of the pulsar magnetosphere. |
| Copyright: | Marta Cholewa |
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