RUI: Dynamic Ultra-Compact Ionized Gas regions in the Star-Forming Region W49A: Continuing the Search for Flickering Sources

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The team will use the Karl G. Jansky Very Large Array (VLA) to search for time-variable sources associated with massive stars. Such flickering sources at radio wavelengths suggest that the stars accrete gas in fits and starts. This surprising behavior was predicted from simulations. The expected changes in the radio signals are too small to measure from year to year. But they are big enough to measure from decade to decade. The longevity of the VLA means that the predictions can now be tested. The team will compare their new VLA measurements with those from two decades ago. Recent technical upgrades to this NSF facility will also let the team study the motions of the accreted gas. Undergraduates from underrepresented groups will be heavily involved in the research. The PI and his undergraduates will produce educational posters for middle-school students. They will also lecture at public events at the local campus observatory. The observatory is the well-known center of a scaled model of our Solar System spread throughout Atlanta, Georgia.The team will use the VLA's exquisite spatial resolution and longevity to study W49A, a massive star-forming complex in our Galaxy. Their goals are to (1) search for variations in the size and flux density of its continuum sources of ionized (HII) gas; (2) test the predictions of the simulations; (3) characterize the properties of the spectral lines from the ionized gas; and (4) look for kinematic signatures of continuum flickering.