2011AJ....142..202H

We present new maser emission from ¹⁴NH₃(9,6) in NGC 7538. Our observations include the known spectral features near v_LSR= -60 km/s and -57 km/s and several more features extending to -46 km/s. In three epochs of observation spanning two months we do not detect any variability in the ammonia masers, in contrast to the >10-fold variability observed in other ¹⁴NH₃(9,6) masers in the Galaxy over comparable timescales. We also present observations of water masers in all three epochs for which emission is observed over the velocity range -105 km/s < v_LSR< -4 km/s, including the highest velocity water emission yet observed from NGC 7538. Of the remarkable number of maser species in IRS 1, H₂ O and, now, ¹⁴NH₃ are the only masers known to exhibit emission outside of the velocity range -62 km/s < v_LSR< -51 km/s. However, we find no significant intensity or velocity correlations between the water emission and ammonia emission. We also present a non-detection in the most sensitive search to date toward any source for emission from the CC³²S and CC³⁴S molecules, indicating an age greater than ~10⁴ yr for IRS 1-3. We discuss these findings in the context of embedded stellar cores and recent models of the region.