ORCID Profile
0000-0002-9986-8816
Current Organisation
Argonne National Laboratory
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Publisher: Oxford University Press (OUP)
Date: 13-09-2016
Publisher: American Astronomical Society
Date: 25-06-2019
Publisher: American Astronomical Society
Date: 16-02-2018
Publisher: American Astronomical Society
Date: 2022
Abstract: Analysis of inclusions in primitive meteorites reveals that several short-lived radionuclides (SLRs) with half-lives of 0.1–100 Myr existed in the early solar system (ESS). We investigate the ESS origin of 107 Pd, 135 Cs, and 182 Hf, which are produced by slow neutron captures (the s -process) in asymptotic giant branch (AGB) stars. We modeled the Galactic abundances of these SLRs using the OMEGA+ galactic chemical evolution (GCE) code and two sets of mass- and metallicity-dependent AGB nucleosynthesis yields (Monash and FRUITY). Depending on the ratio of the mean-life τ of the SLR to the average length of time between the formations of AGB progenitors γ , we calculate timescales relevant for the birth of the Sun. If τ / γ ≳ 2, we predict self-consistent isolation times between 9 and 26 Myr by decaying the GCE predicted 107 Pd/ 108 Pd, 135 Cs/ 133 Cs, and 182 Hf/ 180 Hf ratios to their respective ESS ratios. The predicted 107 Pd/ 182 Hf ratio indicates that our GCE models are missing 9%–73% of 107 Pd and 108 Pd in the ESS. This missing component may have come from AGB stars of higher metallicity than those that contributed to the ESS in our GCE code. If τ / γ ≲ 0.3, we calculate instead the time ( T LE ) from the last nucleosynthesis event that added the SLRs into the presolar matter to the formation of the oldest solids in the ESS. For the 2 M ⊙ , Z = 0.01 Monash model we find a self-consistent solution of T LE = 25.5 Myr.
Publisher: American Astronomical Society
Date: 11-10-2019
Publisher: Oxford University Press (OUP)
Date: 04-11-2022
Abstract: Fluorine has many different potential sites and channels of production, making narrowing down a dominant site of fluorine production particularly challenging. In this work, we investigate which sources are the dominant contributors to the galactic fluorine by comparing chemical evolution models to observations of fluorine abundances in Milky Way stars covering a metallicity range of −2 & [Fe/H] & 0.4 and upper limits in the range of −3.4 & [Fe/H] & −2.3. In our models, we use a variety of stellar yield sets in order to explore the impact of varying both asymptotic giant branch (AGB) and massive star yields on the chemical evolution of fluorine. In particular, we investigate different prescriptions for initial rotational velocity in massive stars as well as a metallicity-dependent mix of rotational velocities. We find that the observed [F/O] and [F/Fe] abundance ratios at low metallicity and the increasing trend of [F/Ba] at [Fe/H] ≳ −1 can only be reproduced by chemical evolution models assuming, at all metallicities, a contribution from rapidly rotating massive stars with initial rotational velocities as high as 300 km s−1. A mix of rotational velocities may provide a more physical solution than the sole use of massive stars with vrot = 300 km s−1, which are predicted to overestimate the fluorine and average s-process elemental abundances at [Fe/H] ≳ −1. The contribution from AGB stars is predicted to start at [Fe/H] ≈ −1 and becomes increasingly important at high metallicity, being strictly coupled to the evolution of the nitrogen abundance. Finally, by using modern yield sets, we investigate the fluorine abundances of Wolf–Rayet winds, ruling them out as dominant contributors to the galactic fluorine.
Publisher: Oxford University Press (OUP)
Date: 11-05-2017
Publisher: American Astronomical Society
Date: 07-2022
Abstract: Of all the light elements, the evolution of lithium (Li) in the Milky Way is perhaps the most difficult to explain. Li is difficult to synthesize and is easily destroyed, making most stellar sites unsuitable for producing Li in sufficient quantities to account for the protosolar abundance. For decades, novae have been proposed as a potential explanation for this “Galactic Li problem,” and the recent detection of 7 Be in the ejecta of multiple nova eruptions has breathed new life into this theory. In this work, we assess the viability of novae as dominant producers of Li in the Milky Way. We present the most comprehensive treatment of novae in a galactic chemical evolution code to date, testing theoretically and observationally derived nova Li yields by integrating metallicity-dependent nova ejecta profiles computed using the binary population synthesis code binary _ c with the galactic chemical evolution code OMEGA+ . We find that our galactic chemical evolution models which use observationally derived Li yields account for the protosolar Li abundance very well, while models relying on theoretical nova yields cannot reproduce the protosolar observation. A brief exploration of physical uncertainties including single-stellar yields, the metallicity resolution of our nova treatment, common-envelope physics, and nova accretion efficiencies indicates that this result is robust to physical assumptions. Scatter within the observationally derived Li yields in novae is identified as the primary source of uncertainty, motivating further observations of 7 Be in nova ejecta.
Publisher: EDP Sciences
Date: 12-2020
DOI: 10.1051/0004-6361/202038721
Abstract: We analyze the nucleosynthesis yields of various Type Ia supernova explosion simulations including pure detonations in sub-Chandrasekhar mass white dwarfs double detonations and pure helium detonations of sub-Chandrasekhar mass white dwarfs with an accreted helium envelope a violent merger model of two white dwarfs and deflagrations and delayed detonations in Chandrasekhar mass white dwarfs. We focus on the iron peak elements Mn, Zn, and Cu. To this end, we also briefly review the different burning regimes and production sites of these elements, as well as the results of abundance measurements and several galactic chemical evolution studies. We find that super-solar values of [Mn/Fe] are not restricted to Chandrasekhar mass explosion models. Scenarios including a helium detonation can significantly contribute to the production of Mn, in particular the models proposed for calcium-rich transients. Although Type Ia supernovae are often not accounted for as production sites of Zn and Cu, our models involving helium shell detonations can produce these elements in super-solar ratios relative to Fe. Our results suggest a re-consideration of Type Ia supernova yields in galactic chemical evolution models. A detailed comparison with observations can provide new insight into the progenitor and explosion channels of these events.
Location: Hungary
No related grants have been discovered for Benoit Cote.