Hubble UV Legacy Library of Young Stars as Essential Standards ("ULLYSES")

The Hubble UV Legacy Library of Young Stars as Essential Standards ("ULLYSES") is a Director's Discretionary program devoting ~1,000 HST orbits to the production of an ultraviolet spectroscopic library of young high- and low-mass stars in the local universe. The ULLYSES program uniformly samples the fundamental astrophysical parameter space for each mass regime -- including spectral type, luminosity class, and metallicity for massive OB stars (in the Magellanic Clouds and two other lower-metallicity nearby galaxies) and the mass, and disk accretion rate for low-mass T Tauri stars (in eight young Galactic star forming regions). The data will be gathered over a three-year period, from Cycle 27 through Cycle 29 (2020-2022). The data products are combined from individual, extracted and calibrated spectra obtained with the COS and STIS instruments on-board HST. Products are made using both archival HST data and new HST observations obtained through the ULLYSES program.