The Renaissance of Stellar Black-Hole Detections in The Local Group

Stellar-mass Black holes provide a crucial component in our understanding of massive stars, gravitational-wave events, and stellar clusters. The recent years have seen tremendous advances in the field. On the one hand, ever-increasing computational power allows theorists to compute increasingly realistic models of collapsing stars. On the other hand, modern spectroscopic, photometric, and astrometric missions (VLT, OGLE, Gaia) continuously enable the detection of a growing population of dormant black holes in the Milky Way and the Magellanic Clouds. Motivated by this, our workshop aims to bring together expert observers and theorists to discuss major questions in the field:

• Is the formation of black holes associated with a supernova explosion?
• What governs the mass spectrum of stellar-mass black holes?
• Under which conditions are black holes expected to be dormant?
• How can we detect the plethora of black holes (both binary and single)?
• What are the biases associated with each technique?
• What are the ideal follow-up strategies for candidates detected through large-scale surveys (e.g. Gaia)?
• What constraints will this new population of black holes place on massive stellar evolution theory?

Guided by these questions, the workshop has the following primary aims:

1. For observers to establish and communicate the challenges and biases of black-hole detection methods, both to each other and to theorists.
2. For theorists to provide predictions regarding the prevalence of black holes in various environments, including the full frame of uncertainties.
3. For the community to identify how the observed population of dormant black holes can constrain population synthesis models, and its broader implications (for example, on the formation of gravitational wave sources).
4. For the community to devise black-hole detection and exploitation strategies, with two main corresponding deliverables:  A. an “exploitation strategy document”, and B. a “living catalog of dormant black holes”.