Lorentz Center Workshop

Summary

Massive stars are instrumental to many areas of astrophysics, both in the local universe and at high redshift. The last decade has seen growing evidence of extreme multiplicity rates and a for a large fraction of massive stars to interact with a binary companion before their final explosion. Such interaction has drastic consequences for the further evolution and final fate of both components. However, the exploration of these effects on entire stellar populations, nearby and at high redshift, and on their observational diagnostics, is still in its infancy.  With this Lorentz Workshop@Oort, we aim to bridge the gap between the massive stars and extragalactic communities and explore how binarity affects the role of massive stars as Cosmic Engines and as Cosmic Probes in modern astrophysics.  During this week, we will review the latest observational and theoretical advances and identify critical areas where progress is desirable. 

The format of the workshop is characterized by a very limited number of scheduled talks,  allowing plenty of time for interaction. Participants will have assigned offices and rooms to discuss in smaller groups as needed.  

Lorentz Center webiste: http://www.lorentzcenter.nl/lc/web/2015/707/info.php3?wsid=707&venue=Oort


Practical information (travel, Venue, Lorentz center, tourist information)


Dates: 29 June - 3 July 2015, Leiden, The Netherlands

Practical information: accomodation, travel, tourist info         http://www.lorentzcenter.nl/

Scientific and Local Organizing Committee

co-Chairs

  • Dr. Hugues Sana, European Space Agency / Space Telescope Science Institute, USA
  • Dr. Selma E. de Mink, University of Amsterdam, NL

co-Organizers

  • Dr. Krzysztof Belczynski (University of Warsaw, Poland)
  • Prof. Alexander Heger (Monash Universit, Australia)
  • Prof. Vicky Kalogera (CIERA / Northwestern University, US
  • Dr. Kaitlin Kratter (University of Arizona, US)
  • Prof. Norbert Langer (University of Bonn, Germany)
  • Prof. Philipp Podsiadlowski (Oxford University)

local organizers and supporting students

  • Lorentz Center Staff
  • Drs. Y. Goetberg (University of Amsterdam, NL)
  • Drs. E. Zapartas (University of Amsterdam, NL)


Scientific Rationale

Massive stars have a dual role in the universe and in astrophysics: as cosmic engines and as cosmological probes. A wide variety of astrophysical problems thus rely on the input of models of massive stars. Most of these models treat single stars, but the overwhelming majority of massive stars are now observed to be in higher multiplicity systems. The proposed Lorentz workshop will provide the most complete and first truly interdisciplinary view, from birth to death and from the close to the distant universe, of the importance of one of the most fundamental properties of massive stars: their extreme multiplicity rates. The meeting will allow for the cross fertilization of ideas beyond the borders of the traditional communities and for the identification of key areas where progress is the most desirable if we are to understand distant populations of massive stars and to properly interpret their observations.

The last years have seen growing evidence that the idealized picture of a single massive star living its life in isolation is oversimplified: a very significant – possibly dominant – fraction of all massive stars will experience interaction with a binary companion before its final explosion as a supernova or gamma-ray burst. Such interaction has drastic consequences for the further evolution and final fate of both components. However, the exploration of these effects on entire stellar populations – nearby and at high
redshift – is still in its infancy.

If binary interaction among massive stars is indeed ubiquitous, it will leave an imprint on many observable properties of entire young stellar populations including the observed mass functions, integrated fluxes and colors, rotation velocities, nature of their most massive stars (as possible massgainers/mergers), as well as the rate and variety of their final explosions (hydrogen rich versus stripped supernovae, nature of the recently discovered super-luminous supernovae, gamma-ray bursts).

These recent developments have led to an awareness of the importance of properly treating the feedback of massive stars in cosmological simulations. A high fraction of binaries affect the predictions of the models in through their radiative feedback and contribution to heating and (re)ionization, their chemical feedback through the return of nucleosynthetic yields and their mechanical feedback through their injection of momentum as seed of turbulence in the ISM. Similarly, X-ray binaries may play a significant role in the heating and partial ionization of the early Universe.

Large spectroscopic, photometric and transient surveys (such as the VLT FLAMES Tarantula survey, the Galactic O stars Spectroscopic Survey, the HST Legacy UV Survey, the Palomar Transient Factory and Pan-STARRS) are now scrutinizing entire populations of massive stars, and their descendants, with unprecedented details. However, the theoretical insight is often still lagging behinds these new observational constraints. Understanding how binarity impacts the observational diagnostics used at various cosmic scales is therefore a high-priority goal.

A key objective is this meeting is to bridge the gap between the massive stars and extragalactic communities, to explore how binarity affects the role of massive stars as Cosmic Engines (through radiative, mechanical and chemical feedback) and as Cosmic Probes (in star forming galaxies or through their bright explosions). This meeting will further bring together observers and theorists to review the latest advances and to identify critical areas where progress is the most desirable in order to anticipate results from near future surveys and observational facilities (GAIA, JWST, 20m- and 30m-class telescopes).

Topics and program

1.     The primordial multiplicity properties of massive stars [Monday]

  • What is the origin of the high multiplicity of massive stars, both in the local universe and for the
    first stars?
  • Can the new observational constraints on the primordial binary properties shed light on the
    preferred massive star formation processes?
  • How well can this knowledge be transferred to the distant universe / first stars?
  • What are the most realistic initial parameters to use to set up realistic binary population
    calculations?

2.     The physics of the binary interaction [Tuesday]

  • What are the most relevant aspects of the binary interaction physics for the feedback of massive
    stars as Cosmic Engines (radiative, mechanical and chemical feedback)?
  • What are the most recent advances and challenges for computational models?
  • What constraints do observations provide? What constraints would theory benefit from? Can we
    reconcile both?

3.     The properties of post-interaction products and their final stages [Wednesday]

  • How do the radiative, chemical and mechanical feedback of post-interaction products differ from non-interacting objects?
  • How do the final stages of post-interaction products differ from non-interacting objects?
  • What constraints do the transients surveys provide?

4.     The cosmological implications I [Thursday]

  • What feedback do massive binaries and massive X-ray binaries provide through cosmic times?
  • What are the most recent advances and challenges of stellar population synthesis (with
    binaries) applied to the low-through-high redshift universe?

5.     Cosmological Implications II [Friday]

  • What are the implications of binarity for the study of the reionization of the universe, the origin
    and fate of chemical elements and the integrated properties of stellar populations (reddening,
    age, mass, stellar mass distribution)?

6.     Directions

  • What lessons did we learn?
  • What are today’s limitations?
  • What are the most promising research directions for the future?