The Duck Redux: An Improved Proper‐Motion Upper Limit for the Pulsar B1757−24 near the Supernova Remnant G5.4–1.2

"The Duck" is a complicated non-thermal radio system, consisting of theenergetic radio pulsar B1757-24, its surrounding pulsar wind nebula G5.27-0.90and the adjacent supernova remnant (SNR) G5.4-1.2. PSR B1757-24 was originallyclaimed to be a young (~15 000 yr) and extreme velocity (>~1500 km/s) pulsarwhich had penetrated and emerged from the shell of the associated SNR G5.4-1.2,but recent upper limits on the pulsar's motion have raised serious difficultieswith this interpretation. We here present 8.5 GHz interferometric observationsof the nebula G5.27-0.90 over a 12-year baseline, doubling the time-span ofprevious measurements. These data correspondingly allow us to halve theprevious upper limit on the nebula's westward motion to 14 milliarcseconds/yr(5-sigma), allowing a substantive reevaluation of this puzzling object. We ruleout the possibility that the pulsar and SNR were formed from a common supernovaexplosion ~15 000 yrs ago as implied by the pulsar's characteristic age, butconclude that an old (>~70 000 yr) pulsar / SNR association, or a situation inwhich the pulsar and SNR are physically unrelated, are both still viableexplanations.