All Outputs (133)

Evidence for radiogenic sulfur-32 in type Ab presolar silicon carbide grains? (2013)
Journal Article
Fujiya, W., Hoppe, P., Zinner, E., Pignatari, M., & Herwig, F. (2013). Evidence for radiogenic sulfur-32 in type Ab presolar silicon carbide grains?. Astrophysical journal. Letters, 776(2), L29. https://doi.org/10.1088/2041-8205/776/2/l29

We report C, Si, and S isotope measurements on 34 presolar silicon carbide grains of Type AB, characterized by 12 C/ 13 C < 10. Nitrogen, Mg-Al-, and Ca-Ti-isotopic compositions were measured on a subset of these grains. Three grains show large 3... Read More about Evidence for radiogenic sulfur-32 in type Ab presolar silicon carbide grains?.

Reproducing the observed abundances in RCB and HdC stars with post-double-degenerate merger models - Constraints on merger and post-merger simulations and physics processes (2013)
Journal Article
Menon, A., Herwig, F., Denissenkov, P. A., Clayton, G. C., Staff, J., Pignatari, M., & Paxton, B. (2013). Reproducing the observed abundances in RCB and HdC stars with post-double-degenerate merger models - Constraints on merger and post-merger simulations and physics processes. The Astrophysical journal, 772(1), 59. https://doi.org/10.1088/0004-637x/772/1/59

The R Coronae Borealis (RCB) stars are hydrogen-deficient, variable stars that are most likely the result of He-CO WD mergers. They display extremely low oxygen isotopic ratios, 16 O/ 18 O ≃ 1-10, 12 C/ 13 C ≥ 100, and enhancements up to 2.6 dex in... Read More about Reproducing the observed abundances in RCB and HdC stars with post-double-degenerate merger models - Constraints on merger and post-merger simulations and physics processes.

Silicon carbide grains of type C provide evidence for the production of the unstable isotope ³²Si in supernovae (2013)
Journal Article
Pignatari, M., Zinner, E., G. Bertolli, M., Trappitsch, R., Hoppe, P., Rauscher, T., Fryer, C., Herwig, F., Hirschi, R., Timmes, F., & Thielemann, F.-K. (2013). Silicon carbide grains of type C provide evidence for the production of the unstable isotope ³²Si in supernovae. Astrophysical journal. Letters, 771(1), Article 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 ³²Si in supernovae.

On the internal pollution mechanisms in the globular cluster NGC 6121(M4): Heavy-element abundances and AGB models (2013)
Journal Article
D’Orazi, V., Campbell, S. W., Lugaro, M., Lattanzio, J. C., Pignatari, M., & Carretta, E. (2013). On the internal pollution mechanisms in the globular cluster NGC 6121(M4): Heavy-element abundances and AGB models. Monthly notices of the Royal Astronomical Society, 433(1), 366-381. https://doi.org/10.1093/mnras/stt728

Globular clusters display significant variations in their light-element content, pointing to the existence of a second stellar generation formed from the ejecta of an earlier generation. The nature of these internal polluters is still a matter of deb... Read More about On the internal pollution mechanisms in the globular cluster NGC 6121(M4): Heavy-element abundances and AGB models.

Measurement of the reaction 17O(α,n)20Ne and its impact on the s process in massive stars (2013)
Journal Article
Best, A., Beard, M., Görres, J., Couder, M., Deboer, R., Falahat, S., Güray, R. T., Kontos, A., Kratz, K.-L., Leblanc, P. J., Li, Q., O'Brien, S., Özkan, N., Pignatari, M., Sonnabend, K., Talwar, R., Tan, W., Uberseder, E., & Wiescher, M. (2013). Measurement of the reaction 17O(α,n)20Ne and its impact on the s process in massive stars. Physical Review C - Nuclear Physics, 87(4), Article 045805. https://doi.org/10.1103/physrevc.87.045805

Background: The ratio between the rates of the reactions 17O ( α , n ) 20Ne and 17O ( α , γ ) 21Ne determines whether 16O is an efficient neutron poison for the s process in massive stars, or if most of the neutrons captured by 16O(n,γ) are recycled... Read More about Measurement of the reaction 17O(α,n)20Ne and its impact on the s process in massive stars.

Abundances of neutron-capture elements in stars of the Galactic disk substructures (2013)
Journal Article
Mishenina, T. V., Pignatari, M., Korotin, S. A., Soubiran, C., Charbonnel, C., Thielemann, F.-K., Gorbaneva, T. I., & Basak, N. Y. (2013). Abundances of neutron-capture elements in stars of the Galactic disk substructures. Astronomy and Astrophysics, 552, A128. https://doi.org/10.1051/0004-6361/201220687

Aims. The aim of this work is to present and discuss the observations of the iron peak (Fe, Ni) and neutron-capture element (Y, Zr, Ba, La, Ce, Nd, Sm, and Eu) abundances for 276 FGK dwarfs, located in the Galactic disk with metallicity-1 < [Fe/H]... Read More about Abundances of neutron-capture elements in stars of the Galactic disk substructures.

Production of carbon-rich presolar grains from massive stars (2013)
Journal Article
Pignatari, M., Wiescher, M., Timmes, F., De Boer, R. J., Thielemann, F. K., Fryer, C., Heger, A., Herwig, F., & Hirschi, R. (2013). Production of carbon-rich presolar grains from massive stars. Astrophysical journal. Letters, 767(2), Article 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.

Neutron capture cross section of unstable Ni63: Implications for stellar nucleosynthesis (2013)
Journal Article
Wallner, A., Vlastou, R., Vlachoudis, V., Vermeulen, M. J., Versaci, R., Ventura, A., Vaz, P., Lederer, C., Massimi, C., Altstadt, S., Andrzejewski, J., Audouin, L., Barbagallo, M., Bécares, V., Bečvář, F., Belloni, F., Berthoumieux, E., Billowes, J., Boccone, V., Bosnar, D., …Variale, V. (2013). Neutron capture cross section of unstable Ni63: Implications for stellar nucleosynthesis. Physical review letters, 110(2), Article 022501. https://doi.org/10.1103/physrevlett.110.022501

The Ni63(n,γ) cross section has been measured for the first time at the neutron time-of-flight facility n-TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged c... Read More about Neutron capture cross section of unstable Ni63: Implications for stellar nucleosynthesis.

The 12C +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., Fryer, C., Herwig, F., Rockefeller, G., & X. Timmes, F. (2013). The 12C +12C reaction and the impact on nucleosynthesis in massive stars. The Astrophysical journal, 762(1), Article 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 12 C( 12 C, α) 20 Ne, 12 C( 12 C, p) 23 Na, and 12 C( 12 C, n) 23 Mg is poorly... Read More about The 12C +12C reaction and the impact on nucleosynthesis in massive stars.

17O(α,γ)21Ne and17O(α, n)20Ne for the weak s process (2012)
Presentation / Conference Contribution
Best, A., Görres, J., Beard, M., Couder, M., deBoer, R., Falahat, S., Güray, R. T., Kontos, A., Kratz, K.-L., LeBlanc, P. J., Li, Q., O'Brien, S., Özkan, N., Pignatari, M., Sonnabend, K., Talwar, R., Tan, W., Uberseder, E., & Wiescher, M. 17O(α,γ)21Ne and17O(α, n)20Ne for the weak s process. Presented at EXOTIC NUCLEI AND NUCLEAR/PARTICLE ASTROPHYSICS (IV). FROM NUCLEI TO STARS: Carpathian Summer School of Physics 2012, Sinaia, Romania

The ratio of the reaction rates of the competing channels 17 O(αγ) 21 Ne and 17 O(α,n) 20 Ne determines the efficiency of 16 O as a neutron poison in the s process in low metallicity rotating stars. It has a large impact on the element production, ei... Read More about 17O(α,γ)21Ne and17O(α, n)20Ne for the weak s process.

The NuGrid Research Platform: A Comprehensive Simulation Approach for Nuclear Astrophysics (2012)
Journal Article
Pignatari, M., & Herwig, F. (2012). The NuGrid Research Platform: A Comprehensive Simulation Approach for Nuclear Astrophysics. Nuclear physics news : a publication of NuPECC and EPS-NPB, 22(4), 18-23. https://doi.org/10.1080/10619127.2012.710142

Since the seminal works by BBFH [1] and Cameron et al. [2] a lot of progress in our understanding of the formation of the elements in stars has been made. Increasing fidelity of spectroscopic observations of stellar abundances as well as high-precis... Read More about The NuGrid Research Platform: A Comprehensive Simulation Approach for Nuclear Astrophysics.

The i-process and CEMP-r/s stars
Presentation / Conference Contribution
Ritter, C., Dardelet, L., Prado, P., Heringer, E., Higgs, C., Sandalski, S., Jones, S., Denissenkov, P., Venn, K., Bertolli, M., Woodward, P., Herwig, F., Pignatari, M., Bertolli, M., Dardelet, L., Denisenkov, P. A., Higgs, C., Jones, S., Masikiv Heringer, E. T., Prado, P., …Venn, K. The i-process and CEMP-r/s stars. Presented at Proceedings of Science

© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. We investigate whether the anomalous elemental abundance patterns in some of the C-enhanced metal-poor-r/s (CEMP-r/s) stars are c... Read More about The i-process and CEMP-r/s stars.

Catching element formation in the act
Other
Fryer, C. L., Timmes, F., Hungerford, A. L., Couture, A., Adams, F., Aoki, W., Arcones, A., Arnett, D., Auchettl, K., Avila, M., Badenes, C., Baron, E., Bauswein, A., Beacom, J., Blackmon, J., Blondin, S., Bloser, P., Boggs, S., Boss, A., Brandt, T., …Pignatari, M. (2019). Catching element formation in the act

Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass b... Read More about Catching element formation in the act.