The Nuclear Reaction Network WinNet (2023)
Journal Article
Reichert, M., Winteler, C., Korobkin, O., Arcones, A., Bliss, J., Eichler, M., Frischknecht, U., Fröhlich, C., Hirschi, R., Jacobi, M., Kuske, J., Martínez-Pinedo, G., Martin, D., Mocelj, D., Rauscher, T., & Thielemann, F.-K. (2023). The Nuclear Reaction Network WinNet. The Astrophysical Journal Supplement, 268(2), Article 66. https://doi.org/10.3847/1538-4365/acf033

We present the state-of-the-art single-zone nuclear reaction network WinNet, which is capable of calculating the nucleosynthetic yields of a large variety of astrophysical environments and conditions. This ranges from the calculation of the primordia... Read More about The Nuclear Reaction Network WinNet.

The effects of surface fossil magnetic fields on massive star evolution: IV. Grids of models at Solar, LMC, and SMC metallicities (2022)
Journal Article
Keszthelyi, Z., de Koter, A., Götberg, Y., Meynet, G., Brands, S. A., Petit, V., Carrington, M., David-Uraz, A., Geen, S. T., Georgy, C., Hirschi, R., Puls, J., Ramalatswa, K. J., Shultz, M. E., & ud-Doula, A. (2022). The effects of surface fossil magnetic fields on massive star evolution: IV. Grids of models at Solar, LMC, and SMC metallicities. Monthly Notices of the Royal Astronomical Society, 517(2), 2028 - 2055. https://doi.org/10.1093/mnras/stac2598

Magnetic fields can drastically change predictions of evolutionary models of massive stars via mass-loss quenching, magnetic braking, and efficient angular momentum transport, which we aim to quantify in this work. We use the MESA software instrument... Read More about The effects of surface fossil magnetic fields on massive star evolution: IV. Grids of models at Solar, LMC, and SMC metallicities.

Very massive star winds as sources of the short-lived radioactive isotope Al-26 (2022)
Journal Article
Hirschi. (2022). Very massive star winds as sources of the short-lived radioactive isotope Al-26. Astronomy & Astrophysics,

Context. The 26Al short-lived radioactive nuclide is the source of the observed galactic diffuse ?-ray emission at 1.8 MeV. While different sources of 26Al have been explored, such as asymptotic giant branch stars, massive stellar winds, and supernov... Read More about Very massive star winds as sources of the short-lived radioactive isotope Al-26.

Grids of stellar models with rotation VII: models from 0.8 to 300 M-circle dot at supersolar metallicity (Z=0.020) (2022)
Journal Article
Yusof, N., Hirschi, R., Eggenberger, P., Ekström, S., Georgy, C., Sibony, Y., Crowther, P. A., Meynet, G., Abu Kassim, H., Aishah Wan Harun, W., Maeder, A., Groh, J. H., Farrell, E., & Murphy, L. (2022). Grids of stellar models with rotation VII: models from 0.8 to 300 M-circle dot at supersolar metallicity (Z=0.020). Monthly Notices of the Royal Astronomical Society, 511(2), 2814 - 2828. https://doi.org/10.1093/mnras/stac230

We present a grid of stellar models at supersolar metallicity (Z = 0.020) extending the previous grids of Geneva models at solar and sub-solar metallicities. A metallicity of Z = 0.020 was chosen to match that of the inner Galactic disc. A modest inc... Read More about Grids of stellar models with rotation VII: models from 0.8 to 300 M-circle dot at supersolar metallicity (Z=0.020).

UVES analysis of red giants in the bulge globular cluster NGC 6522 (2021)
Journal Article
Hirschi. (2021). UVES analysis of red giants in the bulge globular cluster NGC 6522. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/202140815

Context. NGC 6522 is a moderately metal-poor bulge globular cluster ([Fe/H] ~ -1.0), and it is a well-studied representative among a number of moderately metal-poor blue horizontal branch clusters located in the bulge. The NGC 6522 abundance pattern... Read More about UVES analysis of red giants in the bulge globular cluster NGC 6522.

Multidimensional low-Mach number time-implicit hydrodynamic simulations of convective helium shell burning in a massive star (2021)
Journal Article
Hirschi. (2021). Multidimensional low-Mach number time-implicit hydrodynamic simulations of convective helium shell burning in a massive star. Astronomy & Astrophysics, 1-24. https://doi.org/10.1051/0004-6361/202140825

Context. A realistic parametrization of convection and convective boundary mixing in conventional stellar evolution codes is still the subject of ongoing research. To improve the current situation, multidimensional hydrodynamic simulations are used t... Read More about Multidimensional low-Mach number time-implicit hydrodynamic simulations of convective helium shell burning in a massive star.

Convective core entrainment in 1D main-sequence stellar models (2021)
Journal Article
Scott, L. J. A., Hirschi, R., Georgy, C., Arnett, W. D., Meakin, C., Kaiser, E. A., Ekström, S., & Yusof, N. (2021). Convective core entrainment in 1D main-sequence stellar models. Monthly Notices of the Royal Astronomical Society, 503(3), 4208 - 4220. https://doi.org/10.1093/mnras/stab752

3D hydrodynamics models of deep stellar convection exhibit turbulent entrainment at the convective-radiative boundary which follows the entrainment law, varying with boundary penetrability. We implement the entrainment law in the 1D Geneva stellar ev... Read More about Convective core entrainment in 1D main-sequence stellar models.

Reevaluation of the Ne-23(alpha, gamma)Mg-26 and Ne-22(alpha, n)Mg-25 reaction (2021)
Journal Article
Adsley, P., Battino, U., Best, A., Caciolli, A., Guglielmetti, A., Imbriani, G., Jayatissa, H., La Cognata, M., Lamia, L., Masha, E., Massimi, C., Palmerini, S., Tattersall, A., & Hirschi, R. (2021). Reevaluation of the Ne-23(alpha, gamma)Mg-26 and Ne-22(alpha, n)Mg-25 reaction. Physical Review C, 103(1), https://doi.org/10.1103/PhysRevC.103.015805

Background: The competing 22Ne(a,?)26Mg and 22Ne(a,n)25Mg reactions control the production of neutrons for the weak s process in massive and asymptotic giant branch (AGB) stars. In both systems, the ratio between the corresponding reaction rates stro... Read More about Reevaluation of the Ne-23(alpha, gamma)Mg-26 and Ne-22(alpha, n)Mg-25 reaction.

Relative Importance of Convective Uncertainties in Massive Stars (2020)
Journal Article
Kaiser, E. A., Hirschi, R., Arnett, W. D., Georgy, C., Scott, L. J. A., & Cristini, A. (2020). Relative Importance of Convective Uncertainties in Massive Stars. Monthly Notices of the Royal Astronomical Society, 496(2), 1967-1989. https://doi.org/10.1093/mnras/staa1595

In this work, we investigate the impact of uncertainties due to convective boundary mixing (CBM), commonly called ‘overshoot’, namely the boundary location and the amount of mixing at the convective boundary, on stellar structure and evolution. For t... Read More about Relative Importance of Convective Uncertainties in Massive Stars.

Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes (2020)
Journal Article
Belczynski, K., Klencki, J., Fields, C., Olejak, A., Berti, E., Meynet, G., Fryer, C., Holz, D., O’Shaughnessy, R., Brown, D., Bulik, T., Leung, S., Nomoto, K., Madau, P., Hirschi, R., Kaiser, E., Jones, S., Mondal, S., Chruslinska, M., Drozda, P., …Lasota, J.-P. (2020). Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes. Astronomy and Astrophysics, 636, Article A104. https://doi.org/10.1051/0004-6361/201936528

All ten LIGO/Virgo binary black hole (BH-BH) coalescences reported following the O1/O2 runs have near-zero effective spins. There are only three potential explanations for this. If the BH spin magnitudes are large, then: (i) either both BH spin vecto... Read More about Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes.

Wolf-Rayet stars as an evolved stage of stellar life (2016)
Presentation / Conference Contribution
Georgy, C., Ekström, S., Hirschi, R., Meynet, G., Groh, J., & Eggenberger, P. (2015, June). Wolf-Rayet stars as an evolved stage of stellar life. Presented at International Workshop on Wolf-Rayet Stars, Potsdam, Germany

Wolf-Rayet (WR) stars, as they are advanced stages of the life of massive stars, provide a good test for various physical processes involved in the modelling of massive stars, such as rotation and mass loss. In this paper, we show the outputs of the... Read More about Wolf-Rayet stars as an evolved stage of stellar life.

s-process production in rotating massive stars at solar and low metallicities (2015)
Journal Article
Frischknecht, U., Hirschi, R., Pignatari, M., Maeder, A., Meynet, G., Chiappini, C., Thielemann, F.-K., Rauscher, T., Georgy, C., & Ekström, S. (2016). s-process production in rotating massive stars at solar and low metallicities. Monthly Notices of the Royal Astronomical Society, 456(2), 1803 - 1825. https://doi.org/10.1093/mnras/stv2723

Rotation was shown to have a strong impact on the structure and light element nucleosynthesis in massive stars. In particular, models including rotation can reproduce the primary nitrogen observed in halo extremely metal poor (EMP) stars. Additional... Read More about s-process production in rotating massive stars at solar and low metallicities.

Evolution and Nucleosynthesis of Very Massive Stars (2015)
Book Chapter
Hirschi, R. (2015). Evolution and Nucleosynthesis of Very Massive Stars. In Very Massive Stars in the Local Universe (157-198)

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., Fryer, C. L., Stiavelli, M., Chen, K.-J., & 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.

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.

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., Granada, A., Groh, J., Hirschi, R., Mowlavi, N., Yusof, N., Charbonnel, C., Decressin, T., & 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.

NuGrid: s process in massive stars (2009)
Presentation / Conference Contribution
Hirschi, R., Frischknecht, U., Pignatari, M., Thielemann, F.-K., Bennett, M., Diehl, S., Fryer, C., Herwig, F., Hungerford, A., Magkotsios, G., Rockefeller, G., Timmes, F., & Young, P. (2008, July). NuGrid: s process in massive stars. Poster presented at 10th Symposium on Nuclei in the Cosmos, Mackinac Island, Michigan, USA

The s-process production in massive stars at very low metallicities is expected to be negligible due to the low abundance of the neutron source 22Ne, to primary neutron poisons and decreasing iron seed abundances. However, recent models of massive st... Read More about NuGrid: s process in massive stars.

Massive Stars as Cosmic Engines through the Ages (2008)
Journal Article
Hirschi, R. (2008). Massive Stars as Cosmic Engines through the Ages. Proceedings of the International Astronomical Union, 3-16. https://doi.org/10.1017/S1743921308020292

Some useful developments in the model physics are briefly presented, followed by model results on chemical enrichments and WR stars. We discuss the expected rotation velocities of WR stars. We emphasize that the (C+O)/He ratio is a better chemical in... Read More about Massive Stars as Cosmic Engines through the Ages.

Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid (2008)
Preprint / Working Paper
Herwig, F., Fryer, C., Hirschi, R., Bennett, M., L. Fryer, C., Diehl, S., Hungerford, A., Magkotsios, G., Pignatari, M., Rockefeller, G., Timmes, F., X. Timmes, F., & Young, P. Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid

Simulations of nucleosynthesis in astrophysical environments are at the intersection of nuclear physics reaction rate research and astrophysical applications, for example in the area of galactic chemical evolution or near-field cosmology. Unfortunate... Read More about Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid.