ULLYSES Sets Sail: Massive Star Spectroscopy with the HST and the ESO VLT

This Lorentz Center Workshop is devoted to massive star spectroscopy. The workshop will consolidate the community and maximize the scientific output of two unprecedented large complementary observing campaigns being conducted by the Hubble Space Telescope (HST) and the ESO Very Large Telescope (VLT) in 2020-22.

With 30 years in space, the HST is a living astronomical legend. Presently, this is the only telescope which can measure high-resolution ultra-violet (UV) spectra of astronomical objects, such as massive stars. Currently, the HST is assembling a public Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES)} which includes the UV spectra of $> 250$ massive stars in the nearby galaxies. ULLYSES is the single largest program ever implemented by the HST. This is a truly revolutionary development in massive star astrophysics and a true appreciation of its significance for astronomy in general.

The UV spectroscopy can fully unravel its potential only when it is supported by the spectroscopy in optical . The optical spectra of all ULLYSES massive star targets are measured by the ESO Very Large Telescope (VLT) X-Shooter spectrograph. The respectful and fruitful collaboration of various international research teams on exploitation of these unprecedented data-sets is conducted by the ``XShootU'' collaboration.

The key science goals of the workshop, are:

I. to review the current state of the art in the field by sharing scientific insights and know-how in stellar spectroscopy;

II. to benchmark the main data analysis tools and codes; deliberate the development of the next generation codes;

III. to coordinate the future supporting observational campaigns;

IV. to ensure the cross-generation of links in spectroscopy and to attract young scientists and PhD students.

Due to the Covid-19 pandemic, only three online sessions will take place on Monday 13 December, Wednesday 15 December and Friday 16 December. All three sessions will take place in the afternoon CET.