Street Lights and Smoke Detectors: Stellar Early Warning Systems

Debra Wallace

Department of Physics and Astronomy,

Georgia State University

Hot massive stars guide our journey to explore the Universe in much the same way as street-lights illuminate a path to direct one's way on Earth. Observable at great distances due to their intrinsic brightness, their use as calibrators enables us to derive the morphology, chemical yields, Mass-Luminosity Relationship, Initial Mass Functions, and star-formation rates in regions of our own and nearby galaxies, extra-galactic Super Star-forming Clusters (SSCs), and star-forming regions of high red-shift, distant galaxies. Wolf-Rayet (WR) stars, as the last evolutionary phase of these massive stars, serve as the smoke-detectors of the supernovae to come. Only in these objects can one study the immediate precursor's of one of the Universe's most energetic explosive events.

As the cornerstone of so much research effort, the need to fully understand massive stars is crucial and requires study across the electromagnetic spectrum. I will discuss ongoing efforts to quantify these stars, their environments, and their evolution. In doing so, I will address my (and my collaborators) contributions to this effort via our ground-breaking work using the Hubble Space Telescope. We have resolved WR stars at unprecedented resolution using the Wide Field and Planetary Camera II, the Space Telescope Imaging Spectrograph, and the Fine Guidance Sensor 1R to discover and quantify previously unknown companions and clusters. These high resolution observations are essential to provide a true census of the number and astrophysical parameters of massive stars in confined environments where they often occur, and to understand the effects of nearby companions on massive star evolutionary paths.