From discovery to a population: benchmarking stripped stars and companions

The existence of “stripped stars” - stars that have lost their outer layers due to mass transfer in a binary system – has been expected for a long time because most massive stars live in close binary systems that will interact during their lifetime. Binary-stripped stars naturally explain the properties of stripped-envelope supernovae, are important sources of ionizing radiation that help explain the re-ionization of the Universe, and mark a crucial step in the formation of gravitational-wave sources. However, because of their small size and their hot radiation, they are often outshined by their binary companion in the optical and have remained elusive for a long time.

With the very recent discovery of hot stripped stars in the UV, and the serendipitous discovery of cooler stripped stars in the optical in the search for stars with black hole companions, we are now entering a new era. It is finally possible to learn about stripped stars as a population; the first objects discovered are only the tip of the iceberg. In this workshop, we are planning to bring together all the communities working on stripped stars from both observational and theoretical aspects to produce the first benchmark for these fascinating objects and their companions and to optimize strategies to reveal the rest of the iceberg. We are expecting to constrain theoretical models but also to evaluate the implications of their properties for binary mass transfer physics, the supernovae they produce, their ionization power, and for the formation of gravitational-wave sources.

The workshop will have four main goals:

Tip of the iceberg:
How much of the stripped star population remains hidden and how to find it? Optimizing strategies of existing and upcoming large-scale surveys 

From discovery to a population:
Quantifying biases and selection effects to infer a well-characterized population of stripped stars and their companion

Bridging theory with observation:
How do stripped-star binaries fit into the landscape of stellar evolution and crucial mass transfer processes? Identifying links to other populations (subdwarfs, X-ray binaries, supernovae, gravitational-wave sources), defining ways to yield much-needed constraints on models

Stripped stars across Cosmic History:
What is their contribution to the cosmic reionization and UV spectra of stellar populations? Evaluating the final fates of stripped stars, their connections to observed transients, and the role of environmental effects