S Per 1.3 cm Water Masers MERLIN
The water masers are found between 50 and 190 AU from the star. They
form about 100 clumps thought to correspond to individual masing
clouds. The unbeamed size of these clouds, 15 - 20 AU, has never been
measured before. They are distributed in a spherical shell; the
ring-like appearance is caused by tangential beaming showing the
stellar wind in this region is undergoing acceleration due to
radiation pressure on dust grains.
Richards, Cohen(Manchester) and Yates(Herts)
S Per 18 cm OH Masers EVN
In contrast to the water masers the OH masers are brightest at extreme
velocities but close to the line of sight to the star; note that the
faint striations are instrumental effects. A fainter surrounding ring
is clearly resolved for the first time by these VLBI
observations. This shows that the OH masers spatially overlap the
water maser regions, further evidence for the clumpy nature of the
outflow. Preliminary analysis of Zeeman splitting of the OH lines
suggests a magnetic field between -450 and 180 nT at various locations
in the OH shell between 80 and 180 AU from the star.
Masheder (Bristol/JIVE), van Langevelde (JIVE) Richards and Cohen
(Manchester), Greenhill (CfA, Harvard-Smithsonian) and Gray (Bristol)
WR147 6 cm MERLIN
MERLIN images of the X-ray luminous Wolf-Rayet system WR147 reveal
thermal radio emission coincident with the WN8 star and associated
with its stellar wind. The images also show non--thermal emission
along the binary axis and close to the companion B star,
about arcsec to the north, detected by both UKIRT and the the HST. The
shape of the thermal source around the WN8 star shows that its stellar
wind is not spherically symmetric. The non-thermal source is direct
evidence for a colliding-wind origin for the emission, with the B
star being just luminous enough to provide a wind of sufficient
strength.
Williams (ROE) et al. 1997, MNRAS, 289, 10
S140 IRS1 6 cm MERLIN
A MERLIN 6cm map of the thermal emission from the ionized wind of the
massive young stellar object S 140 IRS 1; the resolution is 0.1
arcsec. The wind is highly elongated with dimensions of 400x100
AU. The major axis of the wind is actually perpendicular to the
outflow from this object as observed via a bipolar CO outflow and
near-IR light reflected from the walls of the blue-shifted outflow
lobe. This is the best example yet of equatorial mass loss from
luminous YSOs which may be due to the presence of an accretion disk
feeding the wind or flattening of the wind due to rapid rotation of
the young star.
Hoare (Leeds) and co-workers