First Stars

Collaborators

• Alexander Heger
• Stan Woosley
• Conrad Chan
• James Grimmett
• Bernhard Mueller
• Pamela Vo
• Anna Frebel
• Maria Bergemann
• Norbert Christlieb
• Candace Joggerst
• Weiqun Zhang
• Yong-Zhong Qian
• Daniel Holz
• Evan Scannapieco
• Brian O'Shea
• Daniel Whalen
• Isabelle Baraffe
• Tom Abel

Data

StarFit (tutorial)

Past Conferences

• Chemical Enrichment of the Early Universe, August 9 - August 13, 2004, Santa Fe, New Mexico
• The First Stars and Evolution of the Early Universe, June 19 to July 21, 2006, Institute for Nuclear Theory, University of Washington, Seattle, WA
• First Stars III, Jul 16 to 20, 2007, Santa Fe, NM

Current Projects

Past Projects

Finding the First Cosmic Explosions

(LANL LDRD Project 20080080ER)

• Alexander Heger
• Daniel Holz
• Brian O'Shea
• Daniel Whalen
• Bruce Fryxell
• Candace Church

Coming out of the Cosmic Dark Ages - The First Stars in the Universe

(LANL LDRD Project 20050031DR)

• Alexander Heger
• Hui Li
• Chris Fryer
• Kent Budge
• Shengtai Li
• Stirling Colgate
• Gerry Jungman
• Mike Warren
• Sanjay Reddy
• Joe Carlson
• Aimee Hungerford
• Rob Coker
• Kim New
• Galen Gisler
• Brian O'Shea
• Falk Herwig
• Shannon Cowell
• Nathan Currier
• Dan Whalen
• Andrew Steiner
  
• Mike Norman
• Pedro Marronetti

Publications (not current)

• The Beginning of Stellar Nucleosynthesis
  by A. Heger & S. E. Woosley (2002, to appear in proceedings of the 11th Workshop on Nuclear Astrophysics, Ringberg Castle, eds. E. Müller and W. Hillebrandt, MPA Proceedings, Garching)
• Evolution and Explosion of Very Massive Primordial Stars
  by A. Heger, S. E. Woosley, I. Baraffe, & T. Abel (2002, to appear in Proc. Lighthouses in the Universe, "ESO Astrophysics Symposia", Springer-Verlag)
  
• The Nucleosynthetic Signature of Population III
  by A. Heger & S. E. Woosley (2002, accepted by ApJ, astro-ph/0107037; DATA)
• On the stability of very massive primordial stars
  by I. Baraffe, A. Heger, & S. E. Woosley (2001, ApJ, 550, 890 astro-ph/0009410)
• Pair-Instability Supernovae, Gravity Waves, and Gamma-Ray Transients
  by C. L. Fryer, S. E. Woosley, & A. Heger, (2000, ApJ 541, 1033, astro-ph/0007176)
• Evolution and Nucleosynthesis of Very Massive Primordial Stars
  by A. Heger, I. Baraffe, C. L. Fryer, & S. E. Woosley (2001, Nuclei in the Cosmos 2000, eds. K. Langanke and J. Christensen-Dalsgaard, Amsterdam: Elsevier; Nuclear Physics A, 688, p. 197c - 200c; astro-ph/0010206)
• Evolution and Nucleosynthesis in Massive Stars of Zero Metallicity
  by A. Heger, S. E. Woosley, & R. Waters (2000, in proceedings of the MPA/ESO workshop The first Stars, eds. A. Weiss, T. Abel, & V. Hill, Berlin: Springer Verlag, p. 121)

Resources

Figure 1: Initial-final mass function (IFMF) of non-rotating primordial stars (Z = 0). The x-axis gives the initial stellar mass. The y-axis gives both the final mass of the collapsed remnant (thick black curve) and the mass of the star when the event begins that produces that remnant (e.g., mass loss in AGB stars, supernova explosion for those stars that make a neutron star, etc.; thick gray curve). We distinguish four regimes of initial mass: low mass stars below ~10 M_sun that from white dwarfs; massive stars between ~10 M_sun and ~100 M_sun; very massive stars between ~100 M_sun and ~1000 M_sun; and supermassive stars (arbitrarily) above ~1000 M_sun. Since no mass loss is expected for Z = 0 stars before the final stage, the grey curve corresponds approximately to the line of no mass loss (dotted), except for ~100-140 M_sun where the pulsational pair-instability ejects the outer layers of the star before it collapses, and above ~500 M_sun where pulsational instabilities in red supergiants may lead to significant mass loss. Since the magnitude of the latter is uncertain, lines are dashed. In the low mass regime we assume, even in Z = 0 stars, that mass loss on the asymptotic giant branch (AGB) removes the envelope of the star leaving a CO or NeO white dwarf (though the mechanism and thus the resulting initial-final mass function may differ from solar composition stars). Massive stars are defined by stars that ignite carbon and oxygen burning non-degenerately and do not leave white dwarfs. The hydrogen-rich envelope and parts of the helium core (dash-double-dotted curve) are ejected in a supernova explosion. Below initial masses of ~25 M_sun neutron stars are formed. Above that, black holes form, either in a delayed manner by fall back of the ejecta, or directly during iron core collapse (above ~40 M_sun). The defining characteristic of very massive stars is the electron-positron pair instability after carbon burning. This begins as a pulsational instability for helium cores of ~40 M_sun (M_ZAMS = ~100 M_sun; ZAMS = "zero-age main sequence"). As the mass increases, the pulsations become more violent, ejecting any remaining hydrogen envelope and an increasing fraction of the helium core itself. An iron core can still form in hydrostatic equilibrium in such stars, but it collapses to a black hole. Above a helium core mass, M_He, of ~63 M_sun or about M_ZAMS = 140 M_sun, and on up to M_He = 133 M_sun or about M_ZAMS = 260 M_sun) a single pulse disrupts the star. Above 260 M_sun, the pair instability in non-rotating stars results in complete collapse to a black hole.