6–10 Jul 2026
University of the Western Cape
Africa/Johannesburg timezone
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Constraining Spider Pulsar Binary Plasma Properties Through Radio Eclipses

8 Jul 2026, 16:20
1h 20m
Great Hall ( University of the Western Cape)

Great Hall

University of the Western Cape

Poster Presentation Track D - Astrophysics & Space Science Poster Session 2

Speaker

Thulo Letsele

Description

In spider pulsar binaries, the energetic pulsar wind ablates the companion star, producing dense intrabinary plasma that leads to radio eclipses and complex propagation effects impacting the observed pulsar signal. Previous studies have shown that the properties of these eclipses can constrain the geometry and dynamics of the intrabinary shock formed by the interaction between the pulsar wind and the companion outflow (e.g., Wadiasingh et al. 2017). In this work, we analyse frequency-dependent radio eclipses in selected spider pulsar binaries using multi-frequency radio observations. The structured intrabinary plasma can refract and focus the pulsar radiation, producing observable signatures such as dispersive delays, flux variations, changes in polarisation properties, and changes in eclipse morphology near ingress and egress. We interpret these propagation effects using simplified theoretical models of the intrabinary plasma environment, linking the observed frequency-dependent behaviour to the density distribution and geometry of the shocked plasma surrounding the companion. By combining eclipse morphology, polarisation changes, and dynamic spectral behaviour across multiple observing frequencies with theoretical modelling of plasma propagation effects, we constrain the structure and physical conditions of the intrabinary plasma. These results provide insights into the density distribution and geometry of the pulsar–companion interaction region and contribute to a better understanding of mass loss from the companion and the interaction of pulsar winds with their binary environment.

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Author

Co-authors

Christo Venter (North-West University) Dr Debabrata Deb (Centre for Space Research, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa) Dr Jaikhomba Singha (High Energy Physics, Cosmology & Astrophysics Theory (HEPCAT) Group, Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town 7700, South Africa) Dr Marisa Geyer (High Energy Physics, Cosmology & Astrophysics Theory (HEPCAT) Group, Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town 7700, South Africa) Dr Zorawar Wadiasingh (Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA)

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