  The recently discovered Galactic X-ray transient XTE J1752-223 entered its
first known outburst in 2010, emitting from the X-ray to the radio regimes. Its
general X-ray properties were consistent with those of a black hole candidate
in various spectral states, when ejection of jet components is expected. To
verify this, we carried out very long baseline interferometry (VLBI)
observations. The measurements were carried out with the European VLBI Network
(EVN) and the Very Long Baseline Array (VLBA) at four epochs in 2010 February.
The images at the first three epochs show a moving jet component that is
significantly decelerated by the last epoch, when a new jet component appears
that is likely to be associated with the receding jet side. The overall picture
is consistent with an initially mildly relativistic jet, interacting with the
interstellar medium or with swept-up material along the jet. The brightening of
the receding ejecta at the final epoch can be well explained by initial Doppler
deboosting of the emission in the decelerating jet.
