All Outputs (123)

Evolution of Wolf-Rayet stars as black hole progenitors (2021)
Journal Article
Higgins, E. R., Sander, A. A. C., Vink, J. S., & Hirschi, R. (2021). Evolution of Wolf-Rayet stars as black hole progenitors. Monthly Notices of the Royal Astronomical Society, 505(4), 4874-4889. https://doi.org/10.1093/mnras/stab1548

Evolved Wolf-Rayet stars form a key aspect of massive star evolution, and their strong outflows determine their final fates. In this study, we calculate grids of stellar models for a wide range of initial masses at five metallicities (ranging from so... Read More about Evolution of Wolf-Rayet stars as black hole progenitors.

Convective core sizes in rotating massive stars: I. Constraints from solar metallicity OB field stars (2021)
Journal Article
Martinet, S., Meynet, G., Ekström, S., Simón-Díaz, S., Holgado, G., Castro, N., …Murphy, L. (2021). Convective core sizes in rotating massive stars: I. Constraints from solar metallicity OB field stars. Astronomy & Astrophysics, 648, Article A126. https://doi.org/10.1051/0004-6361/202039426

Context. Spectroscopic studies of Galactic O and B stars show that many stars with masses above 8 M? have been observed in the Hertzsprung-Russell (HR) diagram just beyond the main-sequence (MS) band, as predicted by stellar models computed with a mo... Read More about Convective core sizes in rotating massive stars: I. Constraints from solar metallicity OB field stars.

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., …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.

Constraints on stellar rotation from the evolution of Sr and Ba in the Galactic halo (2021)
Journal Article
Rizzuti, F., Cescutti, G., Matteucci, F., Chieffi, A., Hirschi, R., Limongi, M., & Saro, A. (2021). Constraints on stellar rotation from the evolution of Sr and Ba in the Galactic halo. Monthly Notices of the Royal Astronomical Society, 502(2), 2495-2507. https://doi.org/10.1093/mnras/stab158

Recent studies show that the chemical evolution of Sr and Ba in the Galaxy can be explained if different production sites, hosting r- and s-processes, are taken into account. However, the question of unambiguously identifying these sites is still uns... Read More about Constraints on stellar rotation from the evolution of Sr and Ba in the Galactic halo.

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., …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.

Is GW190521 the merger of black holes from the first stellar generations? (2020)
Journal Article
Farrell, E., Groh, J. H., Hirschi, R., Murphy, L., Kaiser, E., Ekström, S., …Meynet, G. (2021). Is GW190521 the merger of black holes from the first stellar generations?. Monthly Notices of the Royal Astronomical Society, 502(1), L40-L44. https://doi.org/10.1093/mnrasl/slaa196

GW190521 challenges our understanding of the late-stage evolution of massive stars and the effects of the pair-instability in particular. We discuss the possibility that stars at low or zero metallicity could retain most of their hydrogen envelope un... Read More about Is GW190521 the merger of black holes from the first stellar generations?.

Grids of stellar models with rotation: V. Models from 1.7 to 120 Msun at zero metallicity (2020)
Journal Article
Murphy, L. J., Groh, J. H., Ekström, S., Meynet, G., Pezzotti, C., Georgy, C., …Martinet, S. (2021). Grids of stellar models with rotation: V. Models from 1.7 to 120 Msun at zero metallicity. Monthly Notices of the Royal Astronomical Society, 501(2), 2745-2763. https://doi.org/10.1093/mnras/staa3803

Understanding the nature of the first stars is key to understanding the early universe. With new facilities such as JWST we may soon have the first observations of the earliest stellar populations, but to understand these observations we require deta... Read More about Grids of stellar models with rotation: V. Models from 1.7 to 120 Msun at zero metallicity.

Nucleosynthesis in early rotating massive stars and chemical composition of CEMP stars (2020)
Journal Article
Choplin, A., & Hirschi, R. (2020). Nucleosynthesis in early rotating massive stars and chemical composition of CEMP stars. Journal of Physics: Conference Series, 1668(1), Article 012006. https://doi.org/10.1088/1742-6596/1668/1/012006

The first massive stars triggered the onset of chemical evolution by releasing the first metals (elements heavier than helium) in the Universe. The nature of these stars and how the early chemical enrichment took place is still largely unknown. Rotat... Read More about Nucleosynthesis in early rotating massive stars and chemical composition of CEMP stars.

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., …Lasota, J. (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.

The Formation of a 70 M ? Black Hole at High Metallicity (2020)
Journal Article
Hirschi. (2020). The Formation of a 70 M ? Black Hole at High Metallicity. Astrophysical Journal, 113 -113. https://doi.org/10.3847/1538-4357/ab6d77

A 70 black hole (BH) was discovered in the Milky Way disk in a long-period detached binary system (LB-1) with a high-metallicity 8 B star companion. Current consensus on the formation of BHs from high-metallicity stars limits the BH mass to be below... Read More about The Formation of a 70 M ? Black Hole at High Metallicity.

The s process in rotating low-mass AGB stars - Nucleosynthesis calculations in models matching asteroseismic constraints (2019)
Journal Article
Hirschi. (2019). The s process in rotating low-mass AGB stars - Nucleosynthesis calculations in models matching asteroseismic constraints. Astronomy and Astrophysics, A123 -A123. https://doi.org/10.1051/0004-6361/201935476

Aims We investigate the s-process during the AGB phase of stellar models whose cores are enforced to rotate at rates consistent with asteroseismology observations of their progenitors and successors. Methods We calculated new 2 M?, Z = 0.01 mode... Read More about The s process in rotating low-mass AGB stars - Nucleosynthesis calculations in models matching asteroseismic constraints.

The contribution from rotating massive stars to the enrichment in Sr and Ba of the Milky Way (2019)
Journal Article
Rizzuti, F., Cescutti, G., Matteucci, F., Chieffi, A., Hirschi, R., & Limongi, M. (2019). The contribution from rotating massive stars to the enrichment in Sr and Ba of the Milky Way. Monthly Notices of the Royal Astronomical Society, 489(4), 5244 -5255. https://doi.org/10.1093/mnras/stz2505

Most neutron capture elements have a double production by r- and s-processes, but the question of production sites is complex and still open. Recent studies show that including stellar rotation can have a deep impact on nucleosynthesis. We studied th... Read More about The contribution from rotating massive stars to the enrichment in Sr and Ba of the Milky Way.

A direct measurement of the 17O(a,?)21Ne reaction in inverse kinematics and its impact on heavy element production (2019)
Journal Article
Taggart, M., Akers, C., Laird, A., Hager, U., Ruiz, C., Hutcheon, D., …Williams, M. (2019). A direct measurement of the 17O(a,?)21Ne reaction in inverse kinematics and its impact on heavy element production. Physics Letters B, 798(10), Article 134894. https://doi.org/10.1016/j.physletb.2019.134894

During the slow neutron capture process in massive stars, reactions on light elements can both produce and absorb neutrons thereby influencing the final heavy element abundances. At low metallicities, the high neutron capture rate of 16O can inhibit... Read More about A direct measurement of the 17O(a,?)21Ne reaction in inverse kinematics and its impact on heavy element production.

3D Simulations and MLT. I. Renzini’s Critique (2019)
Journal Article
Arnett, W. D., Meakin, C., Hirschi, R., Cristini, A., Georgy, C., Campbell, S., …Mocák, M. (2019). 3D Simulations and MLT. I. Renzini’s Critique. Astrophysical Journal, 882(1), 18. https://doi.org/10.3847/1538-4357/ab21d9

Renzini wrote an influential critique of “overshooting” in mixing-length theory (MLT), as used in stellar evolution codes, and concluded that three-dimensional fluid dynamical simulations were needed. Such simulations are now well tested. Implicit la... Read More about 3D Simulations and MLT. I. Renzini’s Critique.

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 (2019)
Journal Article
Battino, U., Tattersall, A., Lederer-Woods, C., Herwig, F., Denissenkov, P., Hirschi, R., …Collaboration, T. N. (2019). 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, 489(1), 1082 -1098. https://doi.org/10.1093/mnras/stz2158

The production of the neutron-capture isotopes beyond iron that we observe today in the Solar system is the result of the combined contribution of the r-process, the s-process, and possibly the i-process. Low-mass asymptotic giant branch (AGB) (1.5 &... Read More about 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.

Relative Importance of Convective Uncertainties (2019)
Conference Proceeding
Kaiser, E. A., Hirschi, R., Arnett, W. D., Cristini, A., Georgy, C., & Scott, L. J. A. (2019). Relative Importance of Convective Uncertainties. . https://doi.org/10.1007/978-3-030-13876-9_71

Convection plays a key role in the evolution of stars due to energy transport and mixing of composition. Despite its importance, this process is still not well understood. One longstanding conundrum in all 1D stellar evolution codes is the treatment... Read More about Relative Importance of Convective Uncertainties.

Uncertainties in νp-process nucleosynthesis from Monte Carlo variation of reaction rates (2019)
Journal Article
Nishimura (西村信哉), N., Rauscher, T., Hirschi, R., Hirschi, R., Cescutti, G., Murphy, A. S. J., & Fröhlich, C. (2019). Uncertainties in νp-process nucleosynthesis from Monte Carlo variation of reaction rates. Monthly Notices of the Royal Astronomical Society, 489(1), 1379-1396. https://doi.org/10.1093/mnras/stz2104

It has been suggested that a ?p process can occur when hot, dense, and proton-rich matter is expanding within a strong flux of anti-neutrinos. In such an environment, proton-rich nuclides can be produced in sequences of proton captures and (n, p) rea... Read More about Uncertainties in νp-process nucleosynthesis from Monte Carlo variation of reaction rates.

Grids of stellar models with rotation IV. Models from 1.7 to 120 M-circle dot at a metallicity Z=0.0004 (2019)
Journal Article
Groh, J., Ekström, S., Georgy, C., Meynet, G., Choplin, A., Eggenberger, P., …Farrell, E. (2019). Grids of stellar models with rotation IV. Models from 1.7 to 120 M-circle dot at a metallicity Z=0.0004. Astronomy & Astrophysics, 627, Article A24. https://doi.org/10.1051/0004-6361/201833720

The effects of rotation on stellar evolution are particularly important at low metallicity, when mass loss by stellar winds diminishes and the surface enrichment due to rotational mixing becomes relatively more pronounced than at high metallicities.... Read More about Grids of stellar models with rotation IV. Models from 1.7 to 120 M-circle dot at a metallicity Z=0.0004.

Constraining transport of angular momentum in stars Combining asteroseismic observations of core helium burning stars and white dwarfs (2019)
Journal Article
den Hartogh, J., Eggenberger, P., & Hirschi, R. (2019). Constraining transport of angular momentum in stars Combining asteroseismic observations of core helium burning stars and white dwarfs. Astronomy & Astrophysics, 622, 1-10. https://doi.org/10.1051/0004-6361/201834330

Context Transport of angular momentum has been a challenging topic within the stellar evolution community, even more since the recent asteroseismic surveys. All published studies on rotation using asteroseismic observations show a discrepancy betwee... Read More about Constraining transport of angular momentum in stars Combining asteroseismic observations of core helium burning stars and white dwarfs.