LIAC42

Since the first stars lit the Universe, the high-mass stellar population has played a fundamental role in shaping cosmic evolution. A large fraction of these stars display prominent emission from self-ejected disks. These "classical" OBe stars probe a variety of physical processes at the intersection of major topics in stellar astrophysics.

This workshop aims at providing an overview of the current state of the knowledge of these OBe stars, as well as assessing the most urgent open questions. It will offer multi-scales perspectives (small-scale disk/stellar physics, star surfaces, direct surroundings, large-scale  orbits; short to long-term evolution), both theoretically and observationally.

This workshop will take place in Liège from July 13 to July 17. It is placed under the auspices of the IAU working group on active B-stars.

It is organized around four main themes:

1. Why be a Be? Classical OBe stars are the most rapidly rotating near-main sequence stars in the Universe, they are multi-mode pulsators, providing the best opportunity to study the effects of rotation on stellar structure and evolution at high rotation rates. Let's explore the characteristics of Be stars (mass, rotation, pulsations, angular-momentum transport, mixing) and the reason why they are different from other rapidly rotating counterparts without disk.
   Reviewers: Joey Mombarg (CEA) & Coralie Neiner (Obs. Paris-Meudon)
   
2. Never be alone ! The companions to Be stars. A large fraction of OBe stars are thought to be products of binary interaction, which may eventually evolve into double-degenerate mergers. Let's explore the multiplicity evidence (including the role of triples, Be-Xray binaries and gravitational waves...), their mass dependence, and their consequences (notably on the disks).
   Reviewers: Robert Klement (ESO) & Luqian Wang (Chinese Academy of Sciences)
3.  Being encircled - the disks. Classical OBe stars create outflowing gaseous disks, providing an opportunity to study the physics of viscosity and the shedding of angular momentum in real time. Let's explore the initial build-up of disks, its physical processes, the angular-momentum release, the viscous dissipation and radiative ablation,...
   Reviewers: Thomas Rivinius (ESO) & Amanda Caveagna Rubio (Univ. Leeds)
4. Past and future... Exploring single and multiple-star evolutionary channels, up to the endpoints of these systems.
   Reviewers: Pablo Marchant (Univ. Gent) & Floor Broekgaarden (UCSD)

Timeline:

• Submit your talk proposal before March 15 !
• Registration : before May 15
• Start of meeting : July 13

All participants agree to follow the IAU code of conduct

Venue : see the practical informations

SOC:

• Julia Bodensteiner (University of Amsterdam, the Netherlands, co-chair)
• Yaël Nazé (Universite de Liege, Belgium, co-chair)
• Alex Carciofi (University of São Paulo, Brazil)
• Ken Gayley (University of Iowa, USA)
• Anahí Granada (Universidad Nacional De Rio Negro, Argentina)
• Jonathan Labadie-Bartz (Danmarks Tekniske Universitet, Denmark)

LOC:

• Alain Detal (computer support, ULiege)
• Nicole Massin (secretary, ULiege)
• Yaël Nazé (chair, ULiege)
• Gregor Rauw (ULiege)
• Lionel Siess (ULB)

Contact:  liac42@uliege.be ; poster  of the meeting