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A number of ultracompact H II regions in Galactic star forming environmentshave been observed to vary significantly in radio flux density on timescales of10-20 years. Theory predicted that such variations should occur when theaccretion flow that feeds a young massive star becomes unstable and clumpy. Wehave targeted the massive star-forming region W49A with the Karl G. Jansky VeryLarge Array (VLA) for observations at 3.6 cm with the B-configuration at 0.8''resolution, to compare to nearly identical observations taken almost 21 yearsearlier (February 2015 and August 1994). Most of the sources in the crowdedfield of ultracompact and hypercompact H II regions exhibit no significantchanges over this time period. However, one source, W49A/G2, decreased by 20%in peak intensity (from 71+/-4 mJy/beam to 57+/-3 mJy/beam), and 40% inintegrated flux (from 0.109+/-0.011 Jy to 0.067+/-0.007 Jy), where we cite 5sigma errors in peak intensity, and 10% errors in integrated flux. We presentthe radio images of the W49A region at the two epochs, the difference imagethat indicates the location of the flux density decrease, and discussexplanations for the flux density decrease near the position of W49A/G2.

Flux Density Variations at 3.6 cm in the Massive Star-Forming Region W49A