Low-frequency spectra and scattering of pulsars towards the Gum Nebula with the MWA
Year: 2026
Type: article
Abstract: The Gum Nebula is a nearby ionised complex with sight-line-dependent pulsar propagation. We test whether a smooth ionised structure can explain spectral turnovers and pulse broadening towards the Gum Nebula, or whether smaller-scale material is required. We analysed Murchison Widefield Array Voltage Capture System observations of six pulsars over 80--240,MHz, measuring source-dependent sub-band flux densities and combining them with literature data. We fitted power-law, free--free absorption (FFA), and turnover-constrained broken-power-law (BPL) spectra using propagated uncertainties and fractional-error-floor tests. Scattering timescales were measured by forward modelling folded profiles; PSR J0820-4114 and the Vela pulsar were fitted jointly across frequency to separate smooth intrinsic profile evolution from propagation broadening. -6 $ for T_ ̊m e =3 --10^4,K, far above the smooth-shell expectation. PSRs J0737-3039A and J0837-4135 are consistent with τ_ 3 ̊m sc -4 , while PSR J0742-2822 gives α_ ̊m sc =-3.07 =-1.59 ≃-2.74. Neither Galactic electron-density model reproduces both the independent distances and the low-frequency scattering uniformly. and the joint two-component analysis of PSR J0820-4114 gives α_ ̊m sc The Vela pulsar is described by an effective thick-screen model with $α_ ̊m sc The data favour a structured Gum--Vela magneto-ionic environment in which neighbouring sight lines intersect different absorbing and scattering structures; the two effects need not arise in the same plasma component.
Source: Astronomy and Astrophysics
Authors: Ting Yu, Zhifu Gao, Zhongli Zhang, Weicong Jing
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7221800713