Dynamics of the superfine structure in the Orion KL jet

Abstract

We have studied the superfine structure of the active H2O maser region in Orion KL with an angular resolution of ≤ 0.3 × 0.7 mas. The high level of H2O maser emission from 1979-1988 was due to an accretion disk, which is divided into five groups of protoplanetary rings. The peak brightness temperatures of the structures was Tpeak = 1013-14 K. The region is located in the OMC-1 molecular cloud, VLSR ⋍ 7.74 km/s. The cloud amplifies by more than two orders of magnitude the emission from the structures, whose radial velocities are within the maser window ±0.3 km/s. Due to this, the velocity of the H2O super maser emission is constant. In the quiescent period of 1995 a 6 AU jet was discovered, PA = −32°, Tb ⋍ 1011K. In 1998 the jet's brightness temperature increased by more than 3 orders of magnitude. Initially the jet's position angle was PA = −45°, and then changed to PA = −38°. During the period of decreasing emission in 1999 the jet had changed its form and became a helix, that suggests the precession of the rotation axes. In the central part of the jet there is a compact bright source - “the ejector” - with Tejc = 1017 K.