view Abstract Citations (84) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ultracompact structure in the HII region W 49N. Dreher, J. W. ; Johnston, K. J. ; Welch, W. J. ; Walker, R. C. Abstract The brightest region of W49N has been observed at 15 and 22 GHz, and the results are reported. The region consists of seven distinct components spread over about 0.8 pc. One is a limb-brightened shell with radius of about 10 to the 18th cm; the others are ultracompact components with radii less than 10 to the 17th cm and emission measures greater than 100,000 cm to the -6th pc. These components indicate the presence of a very young and luminous cluster of O4 and O9 stars. The H2O masers are found to be directly on the brightest parts of the largest component. The OH masers occur in two groups, one falling toward one of the ultracompact components at about 10 km/s, the other loosely distributed around the margin of the largest component. The presence of so many ultracompact components in this small region cannot be reconciled with the short life-times predicted for these components by current theory. Publication: The Astrophysical Journal Pub Date: August 1984 DOI: 10.1086/162348 Bibcode: 1984ApJ...283..632D Keywords: H Ii Regions; Interstellar Masers; Nebulae; Radio Sources (Astronomy); Cosmic Dust; Hydroxyl Emission; Star Clusters; Water Masers; Astrophysics full text sources ADS | data products SIMBAD (14)