Oral Presentation

Frequency-Dependent Dispersion Measures in PSR B0329+54

Author(s): Shyam S. Sharma, Tetsuya Hashimoto, Tomotsugu Goto, Shotaro Yamasaki, and Simon C.-C. Ho

Presenter: Shyam Sunder (ASIAA, Taipei)

Multiple studies have investigated frequency-dependent dispersion measures (DMs) with variations above 10⁻³ pc cm⁻³ for PSR B0329+54 below 1 GHz. We present results from simultaneous wideband observations of PSR B0329+54 using the upgraded GMRT, covering 300–1460 MHz. Our analysis reveals a pulse feature that aligns consistently with the cold-plasma dispersion law, providing a unique DM across the entire band. In contrast, standard timing techniques like FFTFIT yield frequency-dependent DMs. We investigate the origin of this discrepancy and its link to the pulsar's emission geometry. Our results suggest that the radio emission originates from a compact region within 204 km, centered around 800 km above the neutron star surface—setting the tightest constraint on emission height for this pulsar and significantly improving upon previous dipolar field estimates. We will present these results and discuss their broader significance for understanding pulsars and their magnetic field geometry.