Biography
I completed a MSc in Physics at the Swiss Polytechnic School (EPFL) in Lausanne in 1999 and a PhD in Astrophysics at the Geneva Observatory in 2004. During this PhD, I improved computer models of massive stars to determine their fate (black hole or neutron star), work for which I received the Plantamour-Prevost Prize. I then went to the University of Basel as a Post-doctoral fellow to answer the question: “In which stars are the chemical elements we are made of created?”. Since joining Keele University in 2007 as a RCUK academic fellow, major highlights of my research include: the determination of the mass and fate of the most massive stars known to date, explaining unique abundances in the early Universe and the setting-up and leading of large projects (ERC starting grant for SHYNE project 2012-2017) and collaborations (NUGRID, BRIDGCE, ChETEC COST Action). I was promoted to Reader in 2013 and Professor in 2018.
Research and scholarship
Stars play a key role in the universe through the light they shine, all the chemical elements they produce and the supernova explosions that mark their death. They can be used to probe the universe and its evolution from its infancy. The first stars formed approximately 400 million years after the Big Bang. Even if most of those first stars and subsequent generations are long dead, their chemical "fingerprints" are stored in low-mass stars that have a total lifetime longer than the age of the universe. In particular, extremely metal-poor low-mass stars enable us to study the first stars and the early universe. Using stars and nucleosynthesis as probes of the universe requires a multi-disciplinary approach developing synergy between astronomical observations, nuclear physics experiments and stellar evolution models. The need for multi-disciplinary approaches to tackle key scientific challenges is not new. For example, 100 years ago, Albert Einstein collaborated with mathematician Marcel Grossmann to develop the theory of General Relativity. Multi-disciplinary research is strongly supported in Europe via the ERC frontiers science grants. The UK and Europe play a leading role in the multi-disciplinary research area of stellar nucleosynthesis, thanks to state-of-the-art observing (ESO-VLT, ESA-Gaia) and nuclear experimental (e.g. CERN, LUNA) facilities. For example, Observers find the most metal-poor stars using the VLT, challenging theories of star formation. The LUNA nuclear facility in Italy measured the key reaction of the CNO cycle, the 14N(p,g) reaction in the Gamow window, removing extrapolation uncertainties. Furthermore, next-generation facilities (ESO E-ELT,FAIR@GSI) are being built, which represent billions of Euros in investments.
To maximise return on these huge investments, an improved theoretical framework of interpretation is crucially needed. Theoretical models are lagging far behind observational and experimental efforts. Next-generation stellar evolution models matching these next-generation facilities are therefore the primary objective of the my research.
Due to the complex nature of stars, stellar models would ideally require three-dimensional (3D) hydrodynamic models that include all the relevant physics (convection, rotation, magnetic fields, binary interactions, mass loss). 3D hydro models must use time steps that are at most days (max convective turnover time is ~200 days for red giants). The total lifetime of stars, however, is at least 2 million years. This means it will not be possible to model the full evolution of stars with 3D models in the near future. This explains why most stellar evolution models are limited to (spherically-symmetric) one dimension (1D). There is a long and successful tradition of 1D stellar evolution with many codes developed in different countries. The models produced with these codes have many applications in astrophysics. They are used as a theoretical framework of interpretation for observational surveys (e.g. VLT Flames survey of massive stars), as well as input for supernova simulations, galactic chemical evolution simulations and asteroseismology studies. They are also used to resolve as yet unexplained observations. For example, my group's stellar evolution models explain unique abundances in extremely metal-poor stars (Cescutti,., Hirschi et al 2013) and the oldest globular cluster of the galactic bulge, thus creating for the first time a link between these two populations (Chiappini,.., Hirschi et al 2011, Nature). My group's very massive star models "weighed" the most massive stars discovered to date (Crowther,.,Hirschi et al 2010). The masses determined (up to 320 solar masses at birth) drastically upset the previous upper mass limit of stars, which was around 150 solar masses.
The predictive power of stellar evolution, however, is crippled by 1D prescriptions of 3D phenomena containing free parameters, which need to be tuned to reproduce subsets of observations. A key uncertain prescription in 1D codes is that of convection, in particular convective boundary mixing (CBM). Even though 3D hydro simulations cannot follow the entire evolution of stars, computing power has finally reached the point where convective boundaries can be resolved in the largest simulations. This means that now these simulations can provide the guidance and constraints to build the next generation of stellar evolution models including 3D-hydro-based prescriptions for convective boundary mixing. Very importantly, the constraints from 3D simulations are independent of astronomical observations and thus provide a unique new insight into CBM. The goal of my research is to constrain, improve and establish new 1D prescriptions using 3D simulations and incorporate these new prescriptions into 1D stellar models. These latest 3D models require the largest computers on the planet. The development of these computers represents a multi-disciplinary effort between applied computer science, applied mathematics and (astro-)physics, the other key multi-disciplinary aspect of my research.
The goal of my theoretical research is thus to link major nuclear physics experiments to large astronomical observing programmes, hydrodynamics simulations to stellar models and theoretical stellar astrophysics to the high performance computing industry. To work towards these goals, I currently chair the ChETEC COST Action: http://www.chetec.eu/ .
See my personal web page for further information.
Teaching
Current undergraduate modules taught:
- Nuclear and Particle Physics (PHY-20009)
- Applied Physics and Emerging Technologies (PHY-20033)
- Physics of Fluids (PHY-30030)
- Particle Physics and Accelerators (PHY-30033)
Past undergraduate modules taught:
- Electricity and Magnetism (PHY-10021/23)
- Nature of Matter (PHY-10024)
Selected Publications
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Grids of stellar models with rotation: V. Models from 1.7 to 120 M⊙ at zero metallicity. Monthly Notices of the Royal Astronomical Society. doi> link> full text>2020.
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Relative importance of convective uncertainties in massive stars. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 496(2), 1967-1989. link> doi> full text>2020.
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Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes. ASTRONOMY & ASTROPHYSICS, vol. 636, Article ARTN A104. link> doi> full text>2020.
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The Formation of a 70 M-circle dot Black Hole at High Metallicity. Astrophysical Journal, vol. 890(2), Article ARTN 113. link> doi> link> full text>2020.
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The s process in rotating low-mass AGB stars Nucleosynthesis calculations in models matching asteroseismic constraints. ASTRONOMY & ASTROPHYSICS, vol. 629, Article ARTN A123. link> doi> full text>2019.
Full Publications List show
Journal Articles
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Grids of stellar models with rotation: V. Models from 1.7 to 120 M⊙ at zero metallicity. Monthly Notices of the Royal Astronomical Society. doi> link> full text>2020.
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Relative importance of convective uncertainties in massive stars. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 496(2), 1967-1989. link> doi> full text>2020.
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Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes. ASTRONOMY & ASTROPHYSICS, vol. 636, Article ARTN A104. link> doi> full text>2020.
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The Formation of a 70 M-circle dot Black Hole at High Metallicity. Astrophysical Journal, vol. 890(2), Article ARTN 113. link> doi> link> full text>2020.
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The s process in rotating low-mass AGB stars Nucleosynthesis calculations in models matching asteroseismic constraints. ASTRONOMY & ASTROPHYSICS, vol. 629, Article ARTN A123. link> doi> full text>2019.
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The contribution from rotating massive stars to the enrichment in Sr and Ba of the Milky Way. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 489(4), 5244-5255. link> doi> full text>2019.
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A direct measurement of the O-17(alpha, gamma)Ne-21 reaction in inverse kinematics and its impact on heavy element production. PHYSICS LETTERS B, vol. 798, Article ARTN 134894. link> doi> full text>2019.
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3D Simulations and MLT. I. Renzini's Critique. ASTROPHYSICAL JOURNAL, vol. 882(1), Article ARTN 18. link> doi> full text>2019.
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NuGrid stellar data set - III. Updated low-mass AGB models and s-process nucleosynthesis with metallicities Z=0.01, Z=0.02, and Z=0.03. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 489(1), 1082-1098. link> doi> full text>2019.
- 2019.
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Uncertainties in nu p-process nucleosynthesis from Monte Carlo variation of reaction rates. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 489(1), 1379-1396. link> doi> full text>2019.
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Grids of stellar models with rotation IV. Models from 1.7 to 120 M-circle dot at a metallicity Z=0.0004. Astronomy and Astrophysics, vol. 627, Article ARTN A24. link> doi> full text>2019.
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Dependence of convective boundary mixing on boundary properties and turbulence strength. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 484(4), 4645-4664. link> doi> full text>2019.
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Constraining transport of angular momentum in stars Combining asteroseismic observations of core helium burning stars and white dwarfs. ASTRONOMY & ASTROPHYSICS, vol. 622, Article ARTN A187. link> doi> full text>2019.
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OGLE14-073-a promising pair-instability supernova candidate. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 479(3), 3106-3114. link> doi> full text>2018.
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NuGrid stellar data set - II. Stellar yields from H to Bi for stellar models with M-ZAMS=1-25 M-circle dot and Z=0.0001-0.02. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 480(1), 538-571. link> doi> full text>2018.
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Uncertainties in s-process nucleosynthesis in low-mass stars determined from Monte Carlo variations. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 478(3), 4101-4127. link> doi> full text>2018.
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Nucleosynthesis in the first massive stars. NUCLEAR PHYSICS IN ASTROPHYSICS CONFERENCE (NPA VII), vol. 940, Article ARTN 012021. link> doi> full text>2018.
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Sensitivity to neutron captures and beta-decays of the enhanced s-process in rotating massive stars at low metallicities. NUCLEAR PHYSICS IN ASTROPHYSICS CONFERENCE (NPA VII), vol. 940, Article ARTN 012051. link> doi> full text>2018.
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Uncertainties in the production of p nuclides in thermonuclear supernovae determined by Monte Carlo variations. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 474(3), 3133-3139. link> doi> full text>2017.
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Are some CEMP-s stars the daughters of spinstars?. ASTRONOMY & ASTROPHYSICS, vol. 607, Article ARTN L3. link> doi> full text>2017.
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3D hydrodynamic simulations of carbon burning in massive stars. Monthly Notices of the Royal Astronomical Society, vol. 471(1), 279-300. link> doi> full text>2017.
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Pre-supernova mixing in CEMP-no source stars. ASTRONOMY & ASTROPHYSICS, vol. 605, Article ARTN A63. link> doi> full text>2017.
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Pair-instability Supernova Simulations: Progenitor Evolution, Explosion, and Light Curves. ASTROPHYSICAL JOURNAL, vol. 846(2), Article ARTN 100. link> doi> full text>2017.
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Uncertainties in s-process nucleosynthesis in massive stars determined by Monte Carlo variations. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 469(2), 1752-1767. link> doi> full text>2017.
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Testing a one-dimensional prescription of dynamical shear mixing with a two-dimensional hydrodynamic simulation. ASTRONOMY & ASTROPHYSICS, vol. 604, Article ARTN A25. link> doi> full text>2017.
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The neutron capture process in the He shell in core-collapse supernovae: Presolar silicon carbide grains as a diagnostic tool for nuclear astrophysics. GEOCHIMICA ET COSMOCHIMICA ACTA, vol. 221, 37-46. link> doi> full text>2018.
- 2017.
- 2017.
- 2017.
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Fast evolving pair-instability supernova models: evolution, explosion, light curves. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 464(3), 2854-2865. link> doi> full text>2017.
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Looking for imprints of the first stellar generations in metal-poor bulge field stars. ASTRONOMY & ASTROPHYSICS, vol. 593, Article ARTN A79. link> doi> full text>2016.
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Uncertainties in the production of p nuclei in massive stars obtained from Monte Carlo variations. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 463(4), 4153-4166. link> doi> full text>2016.
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NUGRID STELLAR DATA SET. I. STELLAR YIELDS FROM H TO BI FOR STARS WITH METALLICITIES Z=0.02 and Z=0.01. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, vol. 225(2), Article ARTN 24. link> doi> link> full text>
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APPLICATION OF A THEORY AND SIMULATION-BASED CONVECTIVE BOUNDARY MIXING MODEL FOR AGB STAR EVOLUTION AND NUCLEOSYNTHESIS. ASTROPHYSICAL JOURNAL, vol. 827(1), Article ARTN 30. link> doi> full text>2016.
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How much radioactive nickel does ASASSN-15lh require?. Monthly Notices of the Royal Astronomical Society, vol. 459(1). link> doi> link> full text>2016.
- 2016.
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s-process production in rotating massive stars at solar and low metallicities. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 456(2), 1803-1825. link> doi> link> full text>2016.
- 2015.
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Code dependencies of pre-supernova evolution and nucleosynthesis in massive stars: evolution to the end of core helium burning. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 447(4), 3115-3129. link> doi> full text>2015.
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The role of neutron star mergers in the chemical evolution of the Galactic halo. ASTRONOMY & ASTROPHYSICS, vol. 577, Article ARTN A139. link> doi> full text>2015.
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PAIR-INSTABILITY SUPERNOVAE IN THE LOCAL UNIVERSE (vol 9, 797, 2014). ASTROPHYSICAL JOURNAL, vol. 801(1), Article ARTN 71. link> doi> full text>2015.
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THE FINAL FATE OF STARS THAT IGNITE NEON AND OXYGEN OFF-CENTER: ELECTRON CAPTURE OR IRON CORE-COLLAPSE SUPERNOVA?. ASTROPHYSICAL JOURNAL, vol. 797(2), Article ARTN 83. link> doi> full text>2014.
- 2014.
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THE s-PROCESS ENRICHMENT OF THE GLOBULAR CLUSTERS M4 AND M22. ASTROPHYSICAL JOURNAL, vol. 795(1), Article ARTN 34. link> doi> full text>2014.
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Linking 1D Stellar Evolution to 3D Hydrodynamic Simulations. NEW WINDOWS ON MASSIVE STARS: ASTEROSEISMOLOGY, INTERFEROMETRY AND SPECTROPOLARIMETRY, vol. 307, 98-99. link> doi> full text>2014.
- 2014.
- 2013.
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Grids of stellar models with rotation - III. Models from 0.8 to 120 Msun at a metallicity Z = 0.002. link> doi> link> full text>
- 2013.
- 2013.
- 2013.
- 2013.
- 2013.
- 2013.
- 2012.
- 2012.
- 2012.
- 2012.
- 2012.
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Grids of stellar models with rotation I. Models from 0.8 to 120 M-circle dot at solar metallicity (Z=0.014). ASTRONOMY & ASTROPHYSICS, vol. 537, Article ARTN A146. link> doi> full text>2012.
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Very Massive Stars and the Eddington Limit. FOUR DECADES OF RESEARCH ON MASSIVE STARS, vol. 465, 196-+. link> full text>2012.
- 2011.
- 2011.
- 2011.
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Red Supergiants, Luminous Blue Variables and Wolf-Rayet stars: the single massive star perspective. Societe Royale des Sciences de Liege, Bulletin, vol. 80, p. 266-278 (Proceedings of the 39th Liege Astrophysical Colloquium, held in Li\`ege 12-16 July 2010, edited by G. Rauw, M. De Becker, Y. Naz\'e, J.-M. Vreux, P. Williams). link> full text>
- 2010.
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The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 M-circle dot stellar mass limit. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 408(2), 731-751. link> doi> full text>2010.
- 2010.
- 2010.
- 2010.
- 2008.
- 2008.
- 2008.
- 2008.
- 2008.
- 2008.
- 2008.
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Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid. link> full text>2008.
- 2008.
- 2008.
- 2008.
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The impact of stellar rotation on the CNO abundance patterns in the Milky Way at low metallicities. PoSNIC-IX:080,2006. link> full text>2007.
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Very low-metallicity massive stars: Pre-SN evolution models and primary nitrogen production. Astronomy and Astrophysics, vol. 461(2), 571-583. doi> full text>2007.
- 2006.
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Stellar evolution with rotation:XIII. Predicted GRB rates at various Z. Astronomy and Astrophysics, vol. 443(2), 581-591. doi>2005.
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Yields of rotating stars at solar metallicity. Astronomy and Astrophysics, vol. 433, 1013-1022. doi> full text>2005.
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Stellar evolution with rotation. XII, Pre-supernova models. Astronomy and Astrophysics, vol. 425(2), 649-670. doi>2004.
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Non-standard s-process in massive rotating stars Yields of 10-150 M-circle dot models at Z=10(-3). ASTRONOMY & ASTROPHYSICS, vol. 618, Article ARTN A133. link> doi> full text>2018.
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Spatial Distribution of Nucleosynthesis Products in Cassiopeia A: Comparison Between Observations and 3D Explosion Models. link> full text>
Chapters
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Evolution and Nucleosynthesis of Very Massive Stars. In Very Massive Stars in the Local Universe. Vink JS (Ed.). (vol. 412). Switzerland: Springer. doi>2014.
Other
- 2018.
- 2018.
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Massive star evolution: What we do (not) know. SECOND BRITE-CONSTELLATION SCIENCE CONFERENCE - SMALL SATELLITES - BIG SCIENCE (vol. 5, pp. 37-44). link>2017.
- 2017.
- 2017.
- 2016.
- 2016.
- 2016.
- 2016.
- 2016.
- 2016.
- 2016.
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Theory Considerations For Nucleosynthesis Beyond Fe With Special Emphasis On p-Nuclei In Massive Stars. CETUP 2015 - WORKSHOP ON DARK MATTER, NEUTRINO PHYSICS AND ASTROPHYSICS & PPC 2015 - IXTH INTERNATIONAL CONFERENCE ON INTERCONNECTIONS BETWEEN PARTICLE PHYSICS AND COSMOLOGY (vol. 1743). link> doi>2016.
- 2014.
- 2014.
- 2014.
- 2012.
- 2012.
- 2012.
- 2010.
- 2010.
- 2010.
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Stellar Evolution in the Upper HR Diagram. HOT AND COOL: BRIDGING GAPS IN MASSIVE-STAR EVOLUTION (vol. 425, pp. 13-+). link>2010.
- 2010.
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Theoretical stellar Delta Y/Delta O in the early Universe. LIGHT ELEMENTS IN THE UNIVERSE (pp. 447-+). link>2010.
- 2010.
- 2009.
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HUNTING FOR THE IMPRINTS OF THE FIRST STARS. XII IAU REGIONAL LATIN AMERICAN MEETING (vol. 35, pp. 207-+). link>2009.
- 2009.
- 2008.
- 2008.
- 2008.
- 2008.
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Were the first stars fast rotators?. FIRST STARS III (vol. 990, pp. 325-+). link>2008.
- 2007.
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Mass loss and very low-metallicity stars. UNSOLVED PROBLEMS IN STELLAR PHYSICS (vol. 948, pp. 397-404). link>2007.
- 2007.
- 2006.
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Evolution of rotating stars at very low metallicity. Stellar Evolution at Low Metallicity: Mass Loss, Explosions, Cosmology (vol. 353, pp. 49-62). link>2006.
- 2006.
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Rotating massive stars @ very low Z: High C & N production. Origin of Matter and Evolution of Galaxies (vol. 847, pp. 71-76). link>2006.
- 2006.
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Stellar evolution of massive stars at very low metallicities (With 10 Figures). In S. Roeser (Ed.). Reviews in Modern Astronomy (vol. 19, p. 101-+).2006.
- 2005.
- 2005.
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Chemical abundances and yields from massive stars. Cosmic Abundances as Records of Stellar Evolution and Nucleosynthesis in Honor of David L. Lambert (vol. 336, pp. 79-92). link>2005.
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Effects of rotation on pre-supernova models. 1604-2004: Supernovae as Cosmological Lighthouses (vol. 342, pp. 99-104). link>2005.
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Evolution of the most massive stars. Fate of the Most Massive Stars, Proceedings (vol. 332, pp. 3-13). link>2005.
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Massive rotating stars: Pre-supernova evolution at solar metallicity. 1604-2004: Supernovae as Cosmological Lighthouses (vol. 342, pp. 131-132). link>2005.
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Pre-supernova evolution of rotating massive stars. COSMIC EXPLOSIONS (vol. 99, pp. 209-213). link>2005.
- 2004.
- 2004.
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Stellar yields in CNO from rotating stellar models. CNO IN THE UNIVERSE (vol. 304, pp. 293-301). link>2003.
