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Public Seminar of PhD Candidate: Birth, Evolution, and Environmental Interaction of Pulsars

Speaker

Mr. Zhihong SHI

Affiliation The University of Hong Kong
Date November 26, 2025 (Wednesday)
Time 3:00 p.m.
Venue Room 518A, 5/F, Chong Yuet Ming Physics Building, The University of Hong Kong

Abstract

Pulsars are rapidly rotating neutron stars that serve as powerful probes of extreme physics. To investigate how pulsars are born and evolve, I developed a population synthesis model that incorporates the latest developments in the field and the magneto-rotational evolution processes. Using large samples of radio pulsars from major surveys, the model is fitted with Markov Chain Monte Carlo methods and evaluated using high-dimensional statistical tests. The results favor an exponential magnetic-field decay model driven primarily by Ohmic dissipation, with a characteristic timescale of about 8 million years. This suggests that aging pulsars undergo significant magnetic-field decay.


I also explore how pulsars interact with their environments through bow-shock pulsar wind nebulae (BSPWNe), which form when a fast-moving pulsar creates a cometary, synchrotron-emitting structure in the interstellar medium. Using multi-wavelength observations from 16 telescopes on the Mouse, I identify a spectral break at ~3.5 GHz in the spectrum. Our modeling analysis shows that this break is not caused by synchrotron cooling or self-absorption but instead indicates a low-energy cutoff in the injected particle distribution. This supports a scenario where efficient acceleration only occurs for particles whose Larmor radius exceeds the shock width or the thickness of a magnetic reconnection layer.


Overall, the studies enhance our understanding of neutron star physics and the particle acceleration process in astrophysics.

 

Anyone interested is welcome to attend.