2024 Theses Doctoral

# Global Kinetic Modeling of the Intrabinary Shock in Spider Pulsars

Spider pulsars are compact binary systems consisting of a millisecond pulsar and a low-mass companion. Their X-ray emission, modulated on the orbital period, is interpreted as synchrotron radiation from high-energy electrons accelerated at the intrabinary shock.

In this dissertation, we conduct global two-dimensional particle-in-cell simulations of the intrabinary shock, assuming the shock wraps around the companion star. When the pulsar spin axis is nearly aligned with the orbital angular momentum, the magnetic energy of the relativistic pulsar wind, composed of magnetic stripes of alternating field polarity, efficiently converts to particle energy at the intrabinary shock via shock-driven reconnection. The highest energy particles accelerated by reconnection can stream ahead of the shock and be further accelerated by the upstream motional electric field. In the downstream, further energization is governed by stochastic interactions with the plasmoids or magnetic islands generated by reconnection.

Our results show that the synchrotron spectrum is nearly flat, 𝐹_𝜈 ∝, and the light curve displays two peaks just before and after the pulsar eclipse (superior conjunction), separated in phase by approximately 0.8 rad, with the peak flux exceeding that at inferior conjunction by a factor of ten. Additionally, we consider radiative losses in the form of synchrotron cooling using the reduced Landau-Lifshitz model. We examine three cooled scenarios, with a synchrotron burnoff limit (𝜰_rad) of 120, 60, and 30, comparing these simulations to an uncooled case to understand the impact of radiative losses on particle acceleration and emission.

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## More About This Work

- Academic Units
- Astronomy
- Thesis Advisors
- Sironi, Lorenzo
- Degree
- Ph.D., Columbia University
- Published Here
- September 18, 2024