On the origin of the system PSR B1757-24/SNR G5.4-1.2

A scenariofortheorigin ofthesystem PSR B 1757 24/supernovarem nant(SNR)G 5.4 1.2isproposed. Itissuggested thatboth objectsaretherem nantsofa supernova (SN)thatexploded within a pre-existing bubble blown-up by a runaway m assive star (the SN progenitor) during the nal(W olf-Rayet) phase ofits evolution. This suggestion im plies that (a) the SN blast centre was signi cantly o set from the geom etric centre ofthe wind-blown bubble (i.e.from the centre ofthe future SNR),(b)the bubble was surrounded by a m assive winddriven shell,and (c)the SN blast wave was drastically decelerated by the interaction with the shell.Therefore, onecan understand how therelatively young and low-velocity pulsarPSR B 1757 24 wasableto escapefrom the associated SNR G 5.4 1.2 and why theinferred vectorofpulsartransversevelocity doesnotpointaway from the geom etric centre ofthe SNR.A possible origin ofthe radio source G 5.27 0.9 (located between PSR B 1757 24 and the SNR G 5.4 1.2) is proposed.It is suggested that G 5.27 0.9 is a lobe ofa low M ach num ber (’ 1:7) jet ofgas out owing from the interior ofG 5.4 1.2 through the hole bored in the SNR’s shellby the escaping pulsar.Itisalso suggested thatthe non-therm alem ission ofthe com et-shaped pulsar wind nebula originates in the vicinity ofthe term ination shock and in the cylindric region ofsubsonically m oving shocked pulsar wind. The role ofm agnetized wind-driven shells (swept-up during the W olf-Rayetphase from the am bientinterstellar m edium with the regularm agnetic eld)in form ation ofelongated axisym m etric SNRsisdiscussed.