Large proper motions in the jet of the high-mass YSO cepheus a HW2

Abstract

Using high angular resolution ( 0B25–0B05) Very Large Array (VLA) observations made at 3.6 cm, 1.3 cm, and 7 mm during the period 1991–2004, we report the detection of large proper motions in the components of the radio continuum jet associated with the high-mass young stellar object (YSO) HW2 in the star-forming region Cepheus A. The relative proper motions observed for the two main components of the outflow, moving away from the central source in nearly opposite directions, are of the order of 140 mas yr 1, or 480 km s 1 at a distance of 725 pc. The proper motions observed in the northeast and southwest lobes are not completely antiparallel, and the central elongated source seems to be changing orientation.We discuss possible scenarios to account for these and other observed characteristics.We also report the detection of a 7 mm compact continuum condensation of emission near the center of the thermal radio continuum jet, which we propose as the location of the exciting star.