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The role of neutron star mergers in the chemical evolution of the Galactic halo (2015)
Journal Article
Hirschi. (2015). The role of neutron star mergers in the chemical evolution of the Galactic halo. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/201525698

Context. The dominant astrophysical production site of the r-process elements has not yet been unambiguously identified. The suggested main r-process sites are core-collapse supernovae and merging neutron stars. Aims. We explore the problem of the... Read More about The role of neutron star mergers in the chemical evolution of the Galactic halo.

Linking 1D Stellar Evolution to 3D Hydrodynamical Simulations (2015)
Journal Article
Hirschi, R. (2015). Linking 1D Stellar Evolution to 3D Hydrodynamical Simulations. Proceedings of the International Astronomical Union, 98-99. https://doi.org/10.1017/S1743921314006371

In this contribution we present initial results of a study on convective boundary mixing (CBM) in massive stellar models using the GENEVA stellar evolution code. Before undertaking costly 3D hydrodynamic simulations, it is important to study the gene... Read More about Linking 1D Stellar Evolution to 3D Hydrodynamical Simulations.

The final fate of stars that ignite neon and oxygen off-center: electron capture or iron core-collapse supernova? (2014)
Journal Article
Jones, S., Hirschi, R., & Nomoto, K. (2014). The final fate of stars that ignite neon and oxygen off-center: electron capture or iron core-collapse supernova?. Astrophysical Journal, 797(2), 83. https://doi.org/10.1088/0004-637X/797/2/83

In the ONeMg cores of $8.8-9.5~{\rm M}_\odot$ stars, neon and oxygen burning is ignited off-center. Whether the neon-oxygen flame propagates to the center is critical to determine whether these stars undergo Fe core collapse or electron capture induc... Read More about The final fate of stars that ignite neon and oxygen off-center: electron capture or iron core-collapse supernova?.

Pair-instability supernovae in the local universe (2014)
Journal Article
Whalen, D. J., Smidt, J., Heger, A., Hirschi, R., Yusof, N., Even, W., …Joggerst, C. C. (2014). Pair-instability supernovae in the local universe. Astrophysical Journal, 797(1), Article 9. https://doi.org/10.1088/0004-637X/797/1/9

The discovery of 150-300 M ? stars in the Local Group and pair-instability supernova candidates at low redshifts has excited interest in this exotic explosion mechanism. Realistic light curves for pair-instability supernovae at near-solar metalliciti... Read More about Pair-instability supernovae in the local universe.

High-resolution abundance analysis of red giants in the globular cluster NGC 6522 (2014)
Journal Article
Barbuy, B., Chiappini, C., Cantelli, E., Depagne, E., Pignatari, M., Hirschi, R., …Gómez, A. (2014). High-resolution abundance analysis of red giants in the globular cluster NGC 6522. Astronomy & Astrophysics, 570, A76. https://doi.org/10.1051/0004-6361/201424311

Context. The [Sr/Ba] and [Y/Ba] scatter observed in some galactic halo stars that are very metal-poor and in a few individual stars of the oldest known Milky Way globular cluster NGC 6522 have been interpreted as evidence of early enrichment by massi... Read More about High-resolution abundance analysis of red giants in the globular cluster NGC 6522.

The s-process enrichment of the globular clusters M4 and M22 (2014)
Journal Article
Hirschi. (2014). The s-process enrichment of the globular clusters M4 and M22. Astrophysical Journal, https://doi.org/10.1088/0004-637X/795/1/34

We investigate the enrichment in elements produced by the slow neutron-capture process (s-process) in the globular clusters M4 (NGC 6121) and M22 (NGC 6656). Stars in M4 have homogeneous abundances of Fe and neutron-capture elements, but the entire c... Read More about The s-process enrichment of the globular clusters M4 and M22.

Production of 92Nb, 92Mo, and 146Sm in the gamma-process in SNIa (2014)
Presentation / Conference
Rauscher, T., Travaglio, C., Gallino, R., Nishimura, N., & Hirschi, R. (2014, July). Production of 92Nb, 92Mo, and 146Sm in the gamma-process in SNIa. Paper presented at 13th Symposium on Nuclei in the Cosmos (NIC XIII), Debrecen, Hungary

The knowledge of the production of extinct radioactivities like 92Nb and 146Sm by photodisintegration processes in ccSN and SNIa models is essential for interpreting abundances in meteoritic material and for Galactic Chemical Evolution (GCE). The 92M... Read More about Production of 92Nb, 92Mo, and 146Sm in the gamma-process in SNIa.

Electron Capture and Beta-Decay Rates for the Collapse of O+Ne+Mg Cores (2014)
Journal Article
Hua Lam, Y., Martínez-Pinedo, G., Langanke, K., Jones, S., Hirschi, R., Zegers, R. G. T., & Alex Brown, B. (2014). Electron Capture and Beta-Decay Rates for the Collapse of O+Ne+Mg Cores. EPJ Web of Conferences, 66, Article 07011. https://doi.org/10.1051/epjconf/20146607011

We present a new set of electron (e−) capture and β-decay rates that improves previous calculations by Takahara et al. and Oda et al. by: (a) incorporation of recent charge-exchange and β-decay data, (b) contributions of forbidden transitions, and (c... Read More about Electron Capture and Beta-Decay Rates for the Collapse of O+Ne+Mg Cores.

Evolution and Nucleosynthesis of Very Massive Stars (2014)
Book Chapter
Hirschi, R. (2014). Evolution and Nucleosynthesis of Very Massive Stars. In Very Massive Stars in the Local Universe (157-198). (1). Springer. https://doi.org/10.1007/978-3-319-09596-7_6

In this chapter, after a brief introduction and overview of stellar evolution, we discuss the evolution and nucleosynthesis of very massive stars (VMS: M>100 solar masses) in the context of recent stellar evolution model calculations. This chapter co... Read More about Evolution and Nucleosynthesis of Very Massive Stars.

Grids of stellar models with rotation - III. Models from 0.8 to 120 Msun at a metallicity Z = 0.002 (2013)
Journal Article
Georgy, C., Ekström, S., Eggenberger, P., Meynet, G., Haemmerlé, L., Maeder, A., …Barblan, F. (2013). Grids of stellar models with rotation - III. Models from 0.8 to 120 Msun at a metallicity Z = 0.002. Astronomy & Astrophysics, 558, Article A103. https://doi.org/10.1051/0004-6361/201322178

(shortened) We provide a grid of single star models covering a mass range from 0.8 to 120 Msun with an initial metallicity Z = 0.002 with and without rotation. We discuss the impact of a change in the metallicity by comparing the current tracks with... Read More about Grids of stellar models with rotation - III. Models from 0.8 to 120 Msun at a metallicity Z = 0.002.

ADVANCED BURNING STAGES AND FATE OF 8-10M☉STARS (2013)
Journal Article
Jones, S., Hirschi, R., Nomoto, K., Fischer, T., Timmes, F. X., Herwig, F., …Bertolli, M. G. (in press). ADVANCED BURNING STAGES AND FATE OF 8-10M☉STARS. Astrophysical Journal, 772(2), 150. https://doi.org/10.1088/0004-637x/772/2/150

The reaction of either 4,4′,6,6′-tetramethyl-2,2′-bipyridine, L, or 4,4′,6,6′-tetracarboxy-2,2′-bipyridine, H4L, with Cu(OAc)2·H2O under acidic hydrothermal conditions (50:1 H2O/HNO3; 160 °C) led to the formation of crystalline {[Cu(HL′)(H2O)]·H2O},... Read More about ADVANCED BURNING STAGES AND FATE OF 8-10M☉STARS.

Detailedβ-transition rates for URCA nuclear pairs in 8–10 solar-mass stars (2013)
Journal Article
Toki, H., Suzuki, T., Nomoto, K., Jones, S., & Hirschi, R. Detailedβ-transition rates for URCA nuclear pairs in 8–10 solar-mass stars. Physical Review C - Nuclear Physics, 88(1), Article 015806. https://doi.org/10.1103/physrevc.88.015806

We calculate β-transition rates for URCA nuclear pairs using the sd-shell-model framework of Wildenthal [B. H. Widenthal, Prog. Part. Nucl. Phys. 11, 5 (1984)] with the modified Hamiltonian. We consider many β transitions including excited states nec... Read More about Detailedβ-transition rates for URCA nuclear pairs in 8–10 solar-mass stars.

SILICON CARBIDE GRAINS OF TYPE C PROVIDE EVIDENCE FOR THE PRODUCTION OF THE UNSTABLE ISOTOPE 32 Si IN SUPERNOVAE (2013)
Journal Article
Pignatari, M., Zinner, E., Bertolli, M. G., Trappitsch, R., Hoppe, P., Rauscher, T., …Thielemann, F. (in press). SILICON CARBIDE GRAINS OF TYPE C PROVIDE EVIDENCE FOR THE PRODUCTION OF THE UNSTABLE ISOTOPE 32 Si IN SUPERNOVAE. Astrophysical Journal Letters, 771(1), L7. https://doi.org/10.1088/2041-8205/771/1/l7

Carbon-rich grains are observed to condense in the ejecta of recent core-collapse supernovae (SNe) within a year after the explosion. Silicon carbide grains of type X are C-rich grains with isotopic signatures of explosive SN nucleosynthesis have bee... Read More about SILICON CARBIDE GRAINS OF TYPE C PROVIDE EVIDENCE FOR THE PRODUCTION OF THE UNSTABLE ISOTOPE 32 Si IN SUPERNOVAE.

Evolution and fate of very massive stars (2013)
Journal Article
Yusof, N., Hirschi, R., Meynet, G., Crowther, P. A., Ekström, S., Frischknecht, U., …Schnurr, O. (2013). Evolution and fate of very massive stars. Monthly Notices of the Royal Astronomical Society, 433(2), 1114-1132. https://doi.org/10.1093/mnras/stt794

There is observational evidence that supports the existence of Very Massive Stars in the local universe. First, very massive stars (Mini

The Chemical Evolution of Heavy Elements in Globular Clusters (2013)
Conference Proceeding
Shingles, L. J., Karakas, A. I., & Hirschi, R. (2013). The Chemical Evolution of Heavy Elements in Globular Clusters. . https://doi.org/10.1017/s1743921313007059

We present preliminary results from a chemical evolution model that tracks the composition of heavy elements beyond iron in a globular cluster. The heavy elements can be used as tracers of the nucleosynthetic events that defined the formation and evo... Read More about The Chemical Evolution of Heavy Elements in Globular Clusters.

Thes-process in the Galactic halo: the fifth signature of spinstars in the early Universe? (2013)
Journal Article
Cescutti, G., Chiappini, C., Hirschi, R., Meynet, G., & Frischknecht, U. (2013). Thes-process in the Galactic halo: the fifth signature of spinstars in the early Universe?. Astronomy & Astrophysics, 553, Article A51. https://doi.org/10.1051/0004-6361/201220809

Context. Very old halo stars have previously been found to show at least four different abundance anomalies, which models of fast-rotating massive stars (spinstars) can successfully account for: rise of N/O and C/O, low 12C/13C, and a primary-like ev... Read More about Thes-process in the Galactic halo: the fifth signature of spinstars in the early Universe?.

PRODUCTION OF CARBON-RICH PRESOLAR GRAINS FROM MASSIVE STARS (2013)
Journal Article
Pignatari, M., Wiescher, M., Timmes, F. X., de Boer, R. J., Thielemann, F., Fryer, C., …Hirschi, R. (in press). PRODUCTION OF CARBON-RICH PRESOLAR GRAINS FROM MASSIVE STARS. Astrophysical Journal Letters, 767(2), L22. https://doi.org/10.1088/2041-8205/767/2/l22

About a year after core-collapse supernova, dust starts to condense in the ejecta. In meteorites, a fraction of C-rich presolar grains (e.g., silicon carbide (SiC) grains of Type-X and low density graphites) are identified as relics of these events,... Read More about PRODUCTION OF CARBON-RICH PRESOLAR GRAINS FROM MASSIVE STARS.

THE12C +12C REACTION AND THE IMPACT ON NUCLEOSYNTHESIS IN MASSIVE STARS (2012)
Journal Article
Pignatari, M., Hirschi, R., Wiescher, M., Gallino, R., Bennett, M., Beard, M., …Timmes, F. X. (2013). THE12C +12C REACTION AND THE IMPACT ON NUCLEOSYNTHESIS IN MASSIVE STARS. Astrophysical Journal, 762(1), 31. https://doi.org/10.1088/0004-637x/762/1/31

Despite much effort in the past decades, the C-burning reaction rate is uncertain by several orders of magnitude, and the relative strength between the different channels 12C(12C, α)20Ne, 12C(12C, p)23Na, and 12C(12C, n)23Mg is poorly determined. Add... Read More about THE12C +12C REACTION AND THE IMPACT ON NUCLEOSYNTHESIS IN MASSIVE STARS.