  A scenario for the origin of the system PSR B1757-24/supernova remnant (SNR)
G5.4-1.2 is proposed. It is suggested that both objects are the remnants of a
supernova (SN) that exploded within a pre-existing bubble blown-up by a runaway
massive star (the SN progenitor) during the final (Wolf-Rayet) phase of its
evolution. This suggestion implies that (a) the SN blast centre was
significantly offset from the geometric centre of the wind-blown bubble (i.e.
from the centre of the future SNR), (b) the bubble was surrounded by a massive
wind-driven shell, and (c) the SN blast wave was drastically decelerated by the
interaction with the shell. Therefore, one can understand how the relatively
young and low-velocity pulsar PSR B1757-24 was able to escape from the
associated SNR G5.4-1.2 and why the inferred vector of pulsar transverse
velocity does not point away from the geometric centre of the SNR. A possible
origin of the radio source G5.27-0.9 (located between PSR B1757-24 and the SNR
G5.4-1.2) is proposed. It is suggested that G5.27-0.9 is a lobe of a low Mach
number (\simeq 1.7) jet of gas outflowing from the interior of G5.4-1.2 through
the hole bored in the SNR's shell by the escaping pulsar. It is also suggested
that the non-thermal emission of the comet-shaped pulsar wind nebula originates
in the vicinity of the termination shock and in the cylindric region of
subsonically moving shocked pulsar wind. The role of magnetized wind-driven
shells (swept-up during the Wolf-Rayet phase from the ambient interstellar
medium with the regular magnetic field) in formation of elongated axisymmetric
SNRs is discussed.
