Scintillating insights into PSR~J0737$-$3039A and the interstellar plasma of the Gum Nebula from MeerKAT

TL;DR

This study uses 18 months of MeerKAT observations of PSR J0737-3039A/B to analyze scintillation patterns, revealing properties of the interstellar medium and orbital geometry, and estimating the Gum Nebula's characteristics.

Contribution

It provides a detailed scintillation analysis linking plasma scattering properties to the nebula's structure and the pulsar system's orbital orientation, with implications for understanding the interstellar medium.

Findings

Scattering screen at ~360 pc near Gum Nebula

Nebula expansion velocity estimated at 35 km/s

Orbital inclination constrained to >90°

Abstract

The double pulsar system PSR~J0737$-$3039A/B has enabled some of the most precise tests of strong-field gravity to date. Here, we present a scintillation analysis of the system based on an 18-month observation campaign with the MeerKAT radio telescope. We characterise this interference pattern to infer properties of scattering plasma and the orbital geometry of the system. Our preferred model supports a scattering screen located at a distance of $D_s = 360^{+30}_{-40}$ pc. This moderately anisotropic screen of ionized gas (axial ratio $A_R = 2.4 \pm 0.2$) lies near the edge of the Gum Nebula, which is believed to be a supernova remnant (SNR) or an \HII\, region. We estimate the expansion velocity of the nebula to be $V_{\textrm{s}} = 35 \pm 5$ km s$^{-1}$, implying a SNR age of $t \approx 1$ Myr. We also constrain the orbital orientation and inclination sense of the double pulsar to be $\Omega = 40^{\circ} \pm 3^{\circ}$ and $i > 90^{\circ}$, respectively. Assuming standard scattering geometry, our model yields a distance estimate consistent with the parallax-derived value of $D = 770 \pm 70$ pc from very long baseline interferometry. We conclude by discussing how future models of pulsar scintillation can enhance our understanding of the IISM and the properties of pulsars embedded within or lying behind such intervening structures.