  We present the results of HST/STIS and WFPC2 observations of LkHa 233 and its
environment. LkHa233 is a Herbig Ae/Be star with a collimated bipolar jet. We
investigate optical forbidden lines along the LkHa 233 jet to determine
physical parameters of this jet (electron density n_e, hydrogen ionisation
fraction x_e, electron temperature T_e, and mass density n_H). The knowledge of
these parameters allows us a direct comparison of a jet from a Herbig star with
those from T Tauri stars. The WFPC2 images in broad-band filters clearly show a
dark lane caused either by a circumstellar disk or a dust torus. In the
blueshifted lobe, n_e is close to or above the critical density for [SII] lines
(2.5x10^4 cm^-3) in the first arcsecond and decreases with distance from the
source. The ionisation x_e~0.2-0.6 gently rises for the first 500 AU of the
flow and shows two re-ionisation events further away from the origin. The T_e
varies along the flow between 10^4 K and 3x10^4 K. The (radial) outflow
velocities are ~ 80-160 km s^(-1), and they appear to increase with distance
from the source. In the redshifted lobe, T_e, n_e, x_e, and n_H are all lower
than in the blueshifted lobe, but have the same order of magnitude. All these
derived parameters are just beyond or at the upper limits of those observed for
classical T Tauri star jets. This may indicate that the flows from the higher
mass Herbig stars are indeed scaled-up examples of the same phenomenon as in T
Tauri stars.
