Lunch Session LS9  13 July 2023

Betelgeuse and other runaway stars

Aims and scope

Betelgeuse is a special star in many aspects: It is an unusual runaway star suggesting a complex origin because its high space velocity does not point back to any star forming region. Thus a two-step ejection may have occurred: first a dynamical ejection as a young binary from its birth site, and later a binary supernova ejection to a different direction. This scenario might explain its current relatively high rotation velocity by mass and angular momentum exchange. Alternatively, a merger ? where the expanding Betelgeuse engulfed a companion ? may be responsible.

New results have emerged since the last EAS session on Betelgeuse two years earlier, which concentrated on the Great Dimming data and mass loss: (i) the exceptional Great Dimming appears to be explained by a substantial surface mass ejection and dust formation, (ii) the new binary merger scenario, and (iii) historical records suggesting it was a yellow star two millennia ago, thus constraining its evolutionary path.

In this lunch session, we plan to discuss recent new results and new observations of Betelgeuse and the relevance of being a runaway star for its origin and current unusual properties.

This session will bring together researchers from different fields of stellar astrophysics including, but not only, from those studying Red Supergiants and their theoretical evolutionary models, runaway stars, binary evolution, stellar variability (e.g. the Great Dimming with collaboration with amateur astronomers), supernovae, astro-seismology, interferometry, astrometry, and even historical observations, etc. Open questions include the distance of Betelgeuse: ca. 150 or ca. 200 pc?

We will thus focus on the following three questions: Q1. Why/how is Betelgeuse a 'runaway' ? Q2. Why is Betelgeuse rotating faster ? Q3. What are the implications of Betelgeuse as a yellow star two millennia ago ?

Q1 involves its current space velocity, i.e. the open question of distance, the definitions of walkaway and runaway stars, and the question how it was ejected: dynamical, binary supernova, or by both steps?

Q2 might be explainable by either a merger or mass exchange with its former partner before the supernova.

Q3 would constrain its current evolutionary state (and hence tracks), and might be more of a problem for merger models than for single star models (and more a problem with a larger distance, luminosity, and mass).

We plan to have a few invited overview talks plus contributed talks and posters as well as sufficient time for discussion.

Programme

  • Why/how is Betelgeuse a 'runaway' ?
  • Why is Betelgeuse rotating faster ?
  • What are the implications of Betelgeuse as a yellow star two millennia ago ?

    • Invited speakers

    • Meridith Joyce (Konkoly Observatory, Budapest, Hungary): The Fundamental Parameters of Betelgeuse: Insights and Tensions Three Years after "The Great Dimming
    • Frantisek Dinnbier (Astronomical Institute, Charles University Prague, Czech Rep.): Producing non-retraceable OB stars by dynamical processes in star clusters

    Scientific organisers

    Andrea Dupree (Harvard Smithonian, Cambridge, USA), Stephan Geier (U Potsdam, Germany), Miguel Montarges (Observatoire de Paris, France), Ralph Neuhäuser (U Jena, Germany, chair), Roberto Raddi (U Politècnica de Catalunya, Castelldefels, Spain)

    Contact

    Ralph Neuhäuser, U Jena, Germany, email: ralph.neuhaeuser @ uni-jena.de

    Updated on Thu Mar 02 12:06:15 CET 2023
European Astronomical Society