Investigating Spectral Turnover in Pulsars: Analysis Below 350 MHz and Insights from the Gum Nebula

Yu, Ting

As the sample of pulsar searches grows， the spectral index， a crucial parameter in pulsar research， remains poorly understood in the low-frequency range (particularly below 350 MHz for SKA low frequencies)， especially regarding the phenomenon of spectral turnover. To address this， we conducted a preliminary analysis of pulsar spectra below 350 MHz. The spectral turnover in pulsars may result from absorption within the magnetosphere， loss of radiation mechanism efficiency， or interstellar effects， with possible mechanisms including synchrotron self-absorption (SSA)， free-free absorption (FFA)， or overlay effects. We also targeted pulsars in the Gum Nebula to investigate this turnover， including polarization information， to study the distribution of the interstellar medium (ISM). This research aims to clarify the absorption mechanisms behind the pulsar spectral turnover and the properties of the ionized ISM.