1 research outputs found
Structure and Magnetic Fields in the Precessing Jet System SS 433 I. Multi-Frequency Imaging from 1998
The Very Large Array has been used at five frequencies to study the structure
and linear polarization of SS433 on scales as small as ~0.1" ~ 500 AU. Each jet
consists of a sharp, curving ridge-line at the leading edge, plus significant
trailing off-jet emission, showing that they are enveloped by diffuse
relativistic plasma. No kinematic model with constant jet speed fits our images
on all scales, but they are consistent with variations in jet speed of around
10% around the optical value. Our images show continuous jets with bright
components occurring simultaneously in the two jets roughly every 35 days. When
corrected for projection effects and Doppler boosting, the intensities of the
two jets are intrinsically very similar. Fractional linear polarization up to
20% is present along the ridge-lines, while the core is essentially
unpolarized. The rotation measures are consistent with a foreground screen with
RM ~ +110 radians per meter squared, plus a larger, asymmetrical contribution
close to the core. The apparent magnetic fields in the jets are roughly aligned
with the ridge-lines in most but not all of each jet. The jet is more highly
polarized between the components than in the components themselves, suggesting
that the mechanism that creates them compresses a tangled part of the magnetic
field into a partially-ordered transverse layer. The off-jet emission is
remarkably highly polarized, with m ~ 50% in places, suggesting large-scale
order of the magnetic field surrounding the jets. This polarized signal may
confuse the determination of magnetic field orientations in the jets
themselves. However, the images are consistent with a jet magnetic field that
is everywhere parallel to the helices.Comment: To appear in Ap.J. (27 pages, 12 figures