New Maser Emission from Nonmetastable Ammonia in NGC 7538. III.
  Detection of the (10,6) Transition and a Velocity Gradient
  We present the first astronomical detection of the 14NH3 (J,K) = (10,6) line:
nonthermal emission at several velocities in the Galactic star-forming region
NGC 7538. Using the VLA we have imaged the (10,6) and (9,6) ammonia masers at
several positions within NGC 7538 IRS 1. The individual sources have angular
sizes < 0.1 arcseconds corresponding to brightness temperatures T_B > 1E6 K. We
apply the pumping model of Brown & Cragg, confirming the conjecture that
multiple ortho-ammonia masers can occur with the same value of K. The positions
and velocities of the (10,6) and (9,6) masers are modeled as motion in a
possible disk or torus and are discussed in the context of recent models of the
region.
