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Red Supergiants, Luminous Blue Variables and Wolf-Rayet stars: the single massive star perspective (2011)
Presentation / Conference Contribution
Meynet, G., Georgy, C., Hirschi, R., Maeder, A., Massey, P., Przybilla, N., & Nieva, M.-F. Red Supergiants, Luminous Blue Variables and Wolf-Rayet stars: the single massive star perspective. Presented at Proceedings of the 39th Liege Astrophysical Colloquium, Liège, Belgium

We discuss, in the context of the single star scenario, the nature of the progenitors of Red Supergiants (RSG), of Luminous Blue Variables (LBV) and of Wolf-Rayet (WR) stars. These three different populations correspond to evolved phases of Main Sequ... Read More about Red Supergiants, Luminous Blue Variables and Wolf-Rayet stars: the single massive star perspective.

The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit (2010)
Journal Article
Hirschi. (2010). The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit. Monthly Notices of the Royal Astronomical Society, 731 -751. https://doi.org/10.1111/j.1365-2966.2010.17167.x

Spectroscopic analyses of H-rich WN5-6 stars within the young star clusters NGC 3603 and R136 are presented, using archival HST & VLT spectroscopy, & high spatial resolution near-IR photometry. We derive high T* for the WN stars in NGC 3603 (T*~42+/-... Read More about The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit.

Origin of CEMP stars: What helium and lithium can tell us about CEMP stars? (2010)
Presentation / Conference Contribution
Meynet, G., Hirschi, R., Ekstrom, S., Maeder, A., Georgy, C., Eggenberger, P., & Chiappini, C. Origin of CEMP stars: What helium and lithium can tell us about CEMP stars?

We show that the peculiar surface abundance patterns of Carbon Enhanced Metal Poor (CEMP) stars has been inherited from material having been processed by H- and He-burning phases in a previous generation of stars (hereafter called the ``Source Stars'... Read More about Origin of CEMP stars: What helium and lithium can tell us about CEMP stars?.

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.

44Ti and 56Ni in core-collapse supernovae (2008)
Presentation / Conference Contribution
Magkotsios, G., Timmes, F. X., Wiescher, M., Fryer, C. L., Hungerford, A., Young, P., Bennett, M., Diehl, S., Herwig, F., Hirschi, R., Pignatari, M., & Rockefeller, G. (2008, July). 44Ti and 56Ni in core-collapse supernovae. Paper presented at 10th Symposium on Nuclei in the Cosmos, Mackinac Island, Michigan, USA

We investigate the physical conditions where 44Ti and 56Ni are created in core-collapse supernovae. In this preliminary work we use a series of post-processing network calculations with parametrized expansion profiles that are representative of the w... Read More about 44Ti and 56Ni in core-collapse supernovae.

Difficulties in Probing Nuclear Physics: A Study of Ti and Ni (2008)
Presentation / Conference Contribution
Hungerford, A., Fryer, C. L., Timmes, F. X., Young, P., Bennett, M., Diehl, S., Herwig, F., Hirschi, R., Pignatari, M., Magkotsios, G., & Rockefeller, G. (2008, July). Difficulties in Probing Nuclear Physics: A Study of Ti and Ni. Paper presented at 10th Symposium on Nuclei in the Cosmos, Mackinac Island, Michigan, USA

The nucleosynthetic yield from a supernova explosion depends upon a variety of effects: progenitor evolution, explosion process, details of the nuclear network, and nuclear rates. Especially in studies of integrated stellar yields, simplifications re... Read More about Difficulties in Probing Nuclear Physics: A Study of Ti and Ni.

Developments in physics of massive stars (2007)
Presentation / Conference Contribution
Meynet, G., Ekström, S., Maeder, A., Hirschi, R., Georgy, C., & Beffa, C. Developments in physics of massive stars. Presented at Symposium S250: Massive Stars as Cosmic Engines

New constraints on stellar models are provided by large surveys of massive stars, interferometric observations and asteroseismology. After a review of the main results so far obtained, we present new results from rotating models and discuss compariso... Read More about Developments in physics of massive stars.

Very low metallicity massive star models: Pre-SN evolution and primary nitrogen production (2006)
Journal Article
Hirschi, R. (2006). Very low metallicity massive star models: Pre-SN evolution and primary nitrogen production. Astronomy & Astrophysics, 461(2), 571 - 583. https://doi.org/10.1051/0004-6361%3A20065356

Two series of models were computed. The first series consists of 20 solar mass models with varying initial metallicity (Z=0.02 down to Z=10^{-8}) and rotation (V_{ini}=0-600 km/s). The second one consists of models with an initial metallicity of Z=10... Read More about Very low metallicity massive star models: Pre-SN evolution and primary nitrogen production.

Yields of rotating stars at solar metallicity (2005)
Journal Article
Hirschi, R., Meynet, G., & Maeder, A. (2005). Yields of rotating stars at solar metallicity. Astronomy & Astrophysics, 433(3), 1013-1022. https://doi.org/10.1051/0004-6361%3A20041554

We present a new set of stellar yields obtained from rotating stellar models at solar metallicity covering the massive star range (12-60 solar masses). The stellar models were calculated with the latest version of the Geneva stellar evolution code de... Read More about Yields of rotating stars at solar metallicity.