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

Abstract

‘‘The Duck’’ is a complicated nonthermal radio system, consisting of the energetic radio pulsar B1757� 24, its surrounding pulsar wind nebula G5.27Y0.90, and the adjacent supernova remnant (SNR) G5.4Y1.2. PSR B1757� 24 was originally claimed to be a young (� 15,000 yr) and extreme-velocity (k1500 km s � 1 ) pulsar, which had penetratedandemergedfromtheshelloftheassociatedSNRG5.4Y1.2;butrecentupperlimitsonthepulsar’smotion have raised serious difficulties with this interpretation. We here present 8.5 GHz interferometric observations of the nebula G5.27Y0.90 over a 12 yr baseline, doubling the time span of previous measurements. These data correspondingly allowus to halve theprevious upperlimit onthe nebula’swestward motion to14 masyr � 1 (5 � ), allowing a substantive reevaluation of this puzzling object. We rule out the possibility that the pulsar and SNR were formed from a common supernova explosion � 15,000 yr ago, as implied by the pulsar’s characteristic age, but conclude that an old (k70,000 yr) pulsar/SNR association, or a situation in which the pulsar and SNR are physically unrelated, are both still viable explanations. Subject headingg ISM: individual (G5.4Y1.2) — pulsars: individual (B1757� 24) — radio continuum: ISM — stars: neutron — supernova remnants