A Proper Motion for the Pulsar Wind Nebula G359.23-0.82, "the Mouse," Associated with the Energetic Radio Pulsar J1747-2958

TL;DR

This study measures the proper motion of the pulsar wind nebula 'the Mouse' and its pulsar, revealing their velocity, the interstellar medium density, and implications for pulsar age and evolution, challenging previous assumptions.

Contribution

First direct measurement of the proper motion of the Mouse nebula and its pulsar, providing new insights into their velocity, age, and the local interstellar environment.

Findings

Proper motion of 12.9±1.8 mas/yr for the nebula and pulsar.

Transverse velocity of approximately 306±43 km/s at 5 kpc.

Lower age limit of 163 kyr for the pulsar, exceeding its spin-down age.

Abstract

The "Mouse" (PWN G359.23-0.82) is a spectacular bow shock pulsar wind nebula, powered by the radio pulsar J1747-2958. The pulsar and its nebula are presumed to have a high space velocity, but their proper motions have not been directly measured. Here we present 8.5 GHz interferometric observations of the Mouse nebula with the Very Large Array, spanning a time baseline of 12 yr. We measure eastward proper motion for PWN G359.23-0.82 (and hence indirectly for PSR J1747-2958) of 12.9+/-1.8 mas/yr, which at an assumed distance of 5 kpc corresponds to a transverse space velocity of 306+/-43 km/s. Considering pressure balance at the apex of the bow shock, we calculate an in situ hydrogen number density of approximately 1.0(-0.2)(+0.4) cm^(-3) for the interstellar medium through which the system is traveling. A lower age limit for PSR J1747-2958 of 163(-20)(+28) kyr is calculated by considering its potential birth site. The large discrepancy with the pulsar's spin-down age of 25 kyr is possibly explained by surface dipole magnetic field growth on a timescale ~15 kyr, suggesting possible future evolution of PSR J1747-2958 to a different class of neutron star. We also argue that the adjacent supernova remnant G359.1-0.5 is not physically associated with the Mouse system but is rather an unrelated object along the line of sight.