This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
We compare literature data for the isotopic ratios of Zr, Sr, and Ba from analysis of single mete... more We compare literature data for the isotopic ratios of Zr, Sr, and Ba from analysis of single meteoritic stardust silicon carbide (SiC) grains to new predictions for the slow neutron-capture process (the s process) in metal-rich asymptotic giant branch (AGB) stars. The models have initial metallicities Z = 0.014 (solar) and Z = 0.03 (twice-solar) and initial masses 2-4.5 M , selected such as the condition C/O>1 for the formation of SiC is achieved. Because of the higher Fe abundance, the twice-solar metallicity models result in a lower number of total free neutrons released by the 13 C(α,n) 16 O neutron source. Furthermore, the highest-mass (4-4.5 M) AGB stars of twice-solar metallicity present a milder activation of the 22 Ne(α,n) 25 Mg neutron source than their solar metallicity counterparts, due to cooler temperatures resulting from the effect of higher opacities. They also have a lower amount of the 13 C neutron source than the lower-mass models, following their smaller He-rich region. The combination of these different effects allows our AGB models of twice-solar metallicity to provide a match to the SiC data without the need to consider large variations in the features of the 13 C neutron source nor neutron-capture processes different from the s process. This raises the question if the AGB parent stars of meteoritic SiC
While modelling the galactic chemical evolution (GCE) of stable elements provides insights to the... more While modelling the galactic chemical evolution (GCE) of stable elements provides insights to the formation history of the Galaxy and the relative contributions of nucleosynthesis sites, modelling the evolution of short-lived radioisotopes (SLRs) can provide supplementary timing information on recent nucleosynthesis. To study the evolution of SLRs, we need to understand their spatial distribution. Using a 3-dimensional GCE model, we investigated the evolution of four SLRs: 53 Mn, 60 Fe, 182 Hf, and 244 Pu with the aim of explaining detections of recent (within the last ≈ 1 − 20 Myr) deposition of live 53 Mn, 60 Fe, and 244 Pu of extrasolar origin into deep-sea reservoirs. We find that core-collapse supernovae (CCSNe) are the dominant propagation mechanism of SLRs in the Galaxy. This results in the simultaneously arrival of these four SLRs on Earth, although they could have been produced in different astrophysical sites, which can explain why live extrasolar 53 Mn, 60 Fe, and 244 Pu are found within the same, or similar, layers of deep-sea sediments. We predict that 182 Hf should also be found in such sediments at similar depths.
Analysis of bulk meteorite compositions has revealed small isotopic variations due to the presenc... more Analysis of bulk meteorite compositions has revealed small isotopic variations due to the presence of material (e.g., stardust) that preserved the signature of nuclear reactions occurring in specific stellar sites. The interpretation of such anomalies provides evidence for the environment of the birth of the Sun, its accretion process, the evolution of the solar proto-planetary disk, and the formation of the planets. A crucial element of such interpretation is the comparison of the observed anomalies to predictions from models of stellar nucleosynthesis. To date, however, this comparison has been limited to a handful of model predictions. This is mostly because the calculated stellar abundances need to be transformed into a specific representation, which nuclear astrophysicists and stellar nucleosynthesis researchers are not familiar with. Here, we show in detail that this representation is needed to account for mass fractionation effects in meteorite data that can be generated both...
We investigate the origin in the early Solar System of the short-lived radionuclide 244Pu (with a... more We investigate the origin in the early Solar System of the short-lived radionuclide 244Pu (with a half life of 80 Myr) produced by the rapid (r) neutron-capture process. We consider two large sets of r-process nucleosynthesis models and analyse if the origin of 244Pu in the ESS is consistent with that of the other r and slow (s) neutron-capture process radioactive nuclei. Uncertainties on the r-process models come from both the nuclear physics input and the astrophysical site. The former strongly affects the ratios of isotopes of close mass (129I/127I, 244Pu/238U, and 247Pu/235U). The 129I/247Cm ratio, instead, which involves isotopes of a very different mass, is much more variable than those listed above and is more affected by the physics of the astrophysical site. We consider possible scenarios for the evolution of the abundances of these radioactive nuclei in the galactic interstellar medium and verify under which scenarios and conditions solutions can be found for the origin of...
Radioactive nuclei are the key to understanding the circumstances of the birth of our Sun because... more Radioactive nuclei are the key to understanding the circumstances of the birth of our Sun because meteoritic analysis has proven that many of them were present at that time. Their origin, however, has been so far elusive. The ERC-CoG-2016 RADIOSTAR project is dedicated to investigating the production of radioactive nuclei by nuclear reactions inside stars, their evolution in the Milky Way Galaxy, and their presence in molecular clouds. So far, we have discovered that: (i) radioactive nuclei produced by slow (107Pd and 182Hf) and rapid (129I and 247Cm) neutron captures originated from stellar sources —asymptotic giant branch (AGB) stars and compact binary mergers, respectively—within the galactic environment that predated the formation of the molecular cloud where the Sun was born; (ii) the time that elapsed from the birth of the cloud to the birth of the Sun was of the order of 107 years, and (iii) the abundances of the very short-lived nuclei 26Al, 36Cl, and 41Ca can be explained b...
B Bi ir ró ó Tamás, K Ko ov vá ác cs s István János, K Ka ar rá át ts so on n Dávid, S St ta al l... more B Bi ir ró ó Tamás, K Ko ov vá ác cs s István János, K Ka ar rá át ts so on n Dávid, S St ta al ld de er r, , Roland, K Ki ir rá ál ly y Edit, F Fa al lu us s György, F Fa an nc cs si ik k Tamás, S Sá án nd do or rn né é K Ko ov vá ác cs s.. Judit "Száraz" kvarc feonokristályok ignimbritekben-a kitörési folyamatok, a nagy hőmérsékletű lerakódás és a kristályok jellemzőinek hatása a névlegesen vízmentes ásványok dehidratációjára .
The origin of r-process elements Theoretical models predict that the synthesis of heavy elements ... more The origin of r-process elements Theoretical models predict that the synthesis of heavy elements by the rapid neutron capture process (r-process) occurs in extreme astrophysical environments such as neutron star mergers or some types of supernovae. Testing those predictions by comparing them with the isotopic record has been difficult. Côté et al. examined two r-process isotopes, iodine-129 and curium-247, both of which have half-lives of 15.6 million years. Therefore, their ratio remains constant even long after the nucleosynthesis event. The ratio of those isotopes at the time of Solar System formation is recorded in meteorites. Comparing this value with nuclear astrophysics calculations shows that the most likely source was moderately neutron-rich material ejected from a binary neutron star merger. Science , this issue p. 945
Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origi... more Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origin of volatile depletion in the early solar system. Geochimica et Cosmochimica Acta, in press.
Isotope variations of nucleosynthetic origin among solar system solid samples are well documented... more Isotope variations of nucleosynthetic origin among solar system solid samples are well documented, yet the origin of these variations is still uncertain. The observed variability of 54Cr among materials formed in different regions of the protoplanetary disk has been attributed to variable amounts of presolar, chromium-rich oxide (chromite) grains, which exist within the meteoritic stardust inventory and most likely originated from some type of supernova explosion. To investigate if core-collapse supernovae (CCSNe) could be the site of origin of these grains, we analyze yields of CCSN models of stars with initial masses 15, 20, and 25 M ⊙, and solar metallicity. We present an extensive abundance data set of the Cr, Mg, and Al isotopes as a function of enclosed mass. We find cases in which the explosive C ashes produce a composition in good agreement with the observed 54Cr/52Cr and 53Cr/52Cr ratios as well as the 50Cr/52Cr ratios. Taking into account that the signal at atomic mass 50 ...
Enstatite chondrites and aubrites are meteorites that show the closest similarities to the Earth ... more Enstatite chondrites and aubrites are meteorites that show the closest similarities to the Earth in many isotope systems that undergo mass-independent and mass-dependent isotope fractionations. Due to the analytical challenges to obtain high-precision K isotopic compositions in the past, potential differences in K isotopic compositions between enstatite meteorites and the Earth remained uncertain. We report the first high-precision K isotopic compositions of eight enstatite chondrites and four aubrites and find that there is a significant variation of K isotopic compositions among enstatite meteorites (from -2.34 permil to -0.18 permil). However, K isotopic compositions of nearly all enstatite meteorites scatter around the Bulk Silicate Earth (BSE) value. The average K isotopic composition of the eight enstatite chondrites (-0.47 +/- 0.57 permil) is indistinguishable from the BSE value (-0.48 +/- 0.03 permil), thus further corroborating the isotopic similarity between Earth' bui...
The Bakony-Balaton Highland and Nograd-Gomor Volcanic Fields are the two major extensional and po... more The Bakony-Balaton Highland and Nograd-Gomor Volcanic Fields are the two major extensional and post-extensional young alkaline basalt regions within the Carpathian-Pannonian Region. A characteristic volcanic cone have been chosen from both fields, respectively to study silicate melt inclusions in olivine phenocrysts to provide new information to better understanding the evolution of alkaline mafic magma. The alkaline basalts from both locations, showing porphyritic texture, contain forsteritic olivine phenocrysts and Ti-rich augite (micro)phenocrysts. Pecsko basalt also contains plagioclase phenocrysts. The olivine phenocrysts enclose primary and secondary multiphase silicate melt, CO2 fluid, and Cr-spinel inclusions. The groundmass of the alkali basalts consists of Ti-rich clinopyroxene, labradoritic plagioclase, magnetite, glass and ± leucite, ± nepheline. The silicate melt inclusions in olivine phenocrysts consist mostly of TiO2- and Al2O3-rich augite, TiO2- and FeO-rich rhönite,...
The initial inventory of 244Pu in the solar system is lower than the commonly accepted value. Thi... more The initial inventory of 244Pu in the solar system is lower than the commonly accepted value. This has significant implications for Pu-Xe chronology of early atmospheres.
Xenon isotopes in mantle derived rocks provide information on the early differentiation of the si... more Xenon isotopes in mantle derived rocks provide information on the early differentiation of the silicate mantle of our planet. {131,132 134,136}Xe isotopes are produced by the spontaneous fission of two different elements: the now extinct radionuclide 244Pu, and the long-lived 238U. These two parent nuclides, however, yield rather different proportion of fissiogenic Xenon isotopes. Hence, the proportion of Pu- to U-derived fission xenon is indicative of the degree and rate of outgassing of a mantle reservoir. Recent data obtained from Iceland in our lab confirm that the Xenon isotopic composition of the plume source(s) is characterized by lower 136Xe/130Xe ratios than the MORB source and the Iceland plume is more enriched in the Pu-derived Xenon component. These features are interpreted as reflecting different degrees of outgassing and appear not to be the result of preferential recycling of Xenon to the deep mantle. To further investigate how representative the Icelandic measurement...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
We compare literature data for the isotopic ratios of Zr, Sr, and Ba from analysis of single mete... more We compare literature data for the isotopic ratios of Zr, Sr, and Ba from analysis of single meteoritic stardust silicon carbide (SiC) grains to new predictions for the slow neutron-capture process (the s process) in metal-rich asymptotic giant branch (AGB) stars. The models have initial metallicities Z = 0.014 (solar) and Z = 0.03 (twice-solar) and initial masses 2-4.5 M , selected such as the condition C/O>1 for the formation of SiC is achieved. Because of the higher Fe abundance, the twice-solar metallicity models result in a lower number of total free neutrons released by the 13 C(α,n) 16 O neutron source. Furthermore, the highest-mass (4-4.5 M) AGB stars of twice-solar metallicity present a milder activation of the 22 Ne(α,n) 25 Mg neutron source than their solar metallicity counterparts, due to cooler temperatures resulting from the effect of higher opacities. They also have a lower amount of the 13 C neutron source than the lower-mass models, following their smaller He-rich region. The combination of these different effects allows our AGB models of twice-solar metallicity to provide a match to the SiC data without the need to consider large variations in the features of the 13 C neutron source nor neutron-capture processes different from the s process. This raises the question if the AGB parent stars of meteoritic SiC
While modelling the galactic chemical evolution (GCE) of stable elements provides insights to the... more While modelling the galactic chemical evolution (GCE) of stable elements provides insights to the formation history of the Galaxy and the relative contributions of nucleosynthesis sites, modelling the evolution of short-lived radioisotopes (SLRs) can provide supplementary timing information on recent nucleosynthesis. To study the evolution of SLRs, we need to understand their spatial distribution. Using a 3-dimensional GCE model, we investigated the evolution of four SLRs: 53 Mn, 60 Fe, 182 Hf, and 244 Pu with the aim of explaining detections of recent (within the last ≈ 1 − 20 Myr) deposition of live 53 Mn, 60 Fe, and 244 Pu of extrasolar origin into deep-sea reservoirs. We find that core-collapse supernovae (CCSNe) are the dominant propagation mechanism of SLRs in the Galaxy. This results in the simultaneously arrival of these four SLRs on Earth, although they could have been produced in different astrophysical sites, which can explain why live extrasolar 53 Mn, 60 Fe, and 244 Pu are found within the same, or similar, layers of deep-sea sediments. We predict that 182 Hf should also be found in such sediments at similar depths.
Analysis of bulk meteorite compositions has revealed small isotopic variations due to the presenc... more Analysis of bulk meteorite compositions has revealed small isotopic variations due to the presence of material (e.g., stardust) that preserved the signature of nuclear reactions occurring in specific stellar sites. The interpretation of such anomalies provides evidence for the environment of the birth of the Sun, its accretion process, the evolution of the solar proto-planetary disk, and the formation of the planets. A crucial element of such interpretation is the comparison of the observed anomalies to predictions from models of stellar nucleosynthesis. To date, however, this comparison has been limited to a handful of model predictions. This is mostly because the calculated stellar abundances need to be transformed into a specific representation, which nuclear astrophysicists and stellar nucleosynthesis researchers are not familiar with. Here, we show in detail that this representation is needed to account for mass fractionation effects in meteorite data that can be generated both...
We investigate the origin in the early Solar System of the short-lived radionuclide 244Pu (with a... more We investigate the origin in the early Solar System of the short-lived radionuclide 244Pu (with a half life of 80 Myr) produced by the rapid (r) neutron-capture process. We consider two large sets of r-process nucleosynthesis models and analyse if the origin of 244Pu in the ESS is consistent with that of the other r and slow (s) neutron-capture process radioactive nuclei. Uncertainties on the r-process models come from both the nuclear physics input and the astrophysical site. The former strongly affects the ratios of isotopes of close mass (129I/127I, 244Pu/238U, and 247Pu/235U). The 129I/247Cm ratio, instead, which involves isotopes of a very different mass, is much more variable than those listed above and is more affected by the physics of the astrophysical site. We consider possible scenarios for the evolution of the abundances of these radioactive nuclei in the galactic interstellar medium and verify under which scenarios and conditions solutions can be found for the origin of...
Radioactive nuclei are the key to understanding the circumstances of the birth of our Sun because... more Radioactive nuclei are the key to understanding the circumstances of the birth of our Sun because meteoritic analysis has proven that many of them were present at that time. Their origin, however, has been so far elusive. The ERC-CoG-2016 RADIOSTAR project is dedicated to investigating the production of radioactive nuclei by nuclear reactions inside stars, their evolution in the Milky Way Galaxy, and their presence in molecular clouds. So far, we have discovered that: (i) radioactive nuclei produced by slow (107Pd and 182Hf) and rapid (129I and 247Cm) neutron captures originated from stellar sources —asymptotic giant branch (AGB) stars and compact binary mergers, respectively—within the galactic environment that predated the formation of the molecular cloud where the Sun was born; (ii) the time that elapsed from the birth of the cloud to the birth of the Sun was of the order of 107 years, and (iii) the abundances of the very short-lived nuclei 26Al, 36Cl, and 41Ca can be explained b...
B Bi ir ró ó Tamás, K Ko ov vá ác cs s István János, K Ka ar rá át ts so on n Dávid, S St ta al l... more B Bi ir ró ó Tamás, K Ko ov vá ác cs s István János, K Ka ar rá át ts so on n Dávid, S St ta al ld de er r, , Roland, K Ki ir rá ál ly y Edit, F Fa al lu us s György, F Fa an nc cs si ik k Tamás, S Sá án nd do or rn né é K Ko ov vá ác cs s.. Judit "Száraz" kvarc feonokristályok ignimbritekben-a kitörési folyamatok, a nagy hőmérsékletű lerakódás és a kristályok jellemzőinek hatása a névlegesen vízmentes ásványok dehidratációjára .
The origin of r-process elements Theoretical models predict that the synthesis of heavy elements ... more The origin of r-process elements Theoretical models predict that the synthesis of heavy elements by the rapid neutron capture process (r-process) occurs in extreme astrophysical environments such as neutron star mergers or some types of supernovae. Testing those predictions by comparing them with the isotopic record has been difficult. Côté et al. examined two r-process isotopes, iodine-129 and curium-247, both of which have half-lives of 15.6 million years. Therefore, their ratio remains constant even long after the nucleosynthesis event. The ratio of those isotopes at the time of Solar System formation is recorded in meteorites. Comparing this value with nuclear astrophysics calculations shows that the most likely source was moderately neutron-rich material ejected from a binary neutron star merger. Science , this issue p. 945
Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origi... more Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origin of volatile depletion in the early solar system. Geochimica et Cosmochimica Acta, in press.
Isotope variations of nucleosynthetic origin among solar system solid samples are well documented... more Isotope variations of nucleosynthetic origin among solar system solid samples are well documented, yet the origin of these variations is still uncertain. The observed variability of 54Cr among materials formed in different regions of the protoplanetary disk has been attributed to variable amounts of presolar, chromium-rich oxide (chromite) grains, which exist within the meteoritic stardust inventory and most likely originated from some type of supernova explosion. To investigate if core-collapse supernovae (CCSNe) could be the site of origin of these grains, we analyze yields of CCSN models of stars with initial masses 15, 20, and 25 M ⊙, and solar metallicity. We present an extensive abundance data set of the Cr, Mg, and Al isotopes as a function of enclosed mass. We find cases in which the explosive C ashes produce a composition in good agreement with the observed 54Cr/52Cr and 53Cr/52Cr ratios as well as the 50Cr/52Cr ratios. Taking into account that the signal at atomic mass 50 ...
Enstatite chondrites and aubrites are meteorites that show the closest similarities to the Earth ... more Enstatite chondrites and aubrites are meteorites that show the closest similarities to the Earth in many isotope systems that undergo mass-independent and mass-dependent isotope fractionations. Due to the analytical challenges to obtain high-precision K isotopic compositions in the past, potential differences in K isotopic compositions between enstatite meteorites and the Earth remained uncertain. We report the first high-precision K isotopic compositions of eight enstatite chondrites and four aubrites and find that there is a significant variation of K isotopic compositions among enstatite meteorites (from -2.34 permil to -0.18 permil). However, K isotopic compositions of nearly all enstatite meteorites scatter around the Bulk Silicate Earth (BSE) value. The average K isotopic composition of the eight enstatite chondrites (-0.47 +/- 0.57 permil) is indistinguishable from the BSE value (-0.48 +/- 0.03 permil), thus further corroborating the isotopic similarity between Earth' bui...
The Bakony-Balaton Highland and Nograd-Gomor Volcanic Fields are the two major extensional and po... more The Bakony-Balaton Highland and Nograd-Gomor Volcanic Fields are the two major extensional and post-extensional young alkaline basalt regions within the Carpathian-Pannonian Region. A characteristic volcanic cone have been chosen from both fields, respectively to study silicate melt inclusions in olivine phenocrysts to provide new information to better understanding the evolution of alkaline mafic magma. The alkaline basalts from both locations, showing porphyritic texture, contain forsteritic olivine phenocrysts and Ti-rich augite (micro)phenocrysts. Pecsko basalt also contains plagioclase phenocrysts. The olivine phenocrysts enclose primary and secondary multiphase silicate melt, CO2 fluid, and Cr-spinel inclusions. The groundmass of the alkali basalts consists of Ti-rich clinopyroxene, labradoritic plagioclase, magnetite, glass and ± leucite, ± nepheline. The silicate melt inclusions in olivine phenocrysts consist mostly of TiO2- and Al2O3-rich augite, TiO2- and FeO-rich rhönite,...
The initial inventory of 244Pu in the solar system is lower than the commonly accepted value. Thi... more The initial inventory of 244Pu in the solar system is lower than the commonly accepted value. This has significant implications for Pu-Xe chronology of early atmospheres.
Xenon isotopes in mantle derived rocks provide information on the early differentiation of the si... more Xenon isotopes in mantle derived rocks provide information on the early differentiation of the silicate mantle of our planet. {131,132 134,136}Xe isotopes are produced by the spontaneous fission of two different elements: the now extinct radionuclide 244Pu, and the long-lived 238U. These two parent nuclides, however, yield rather different proportion of fissiogenic Xenon isotopes. Hence, the proportion of Pu- to U-derived fission xenon is indicative of the degree and rate of outgassing of a mantle reservoir. Recent data obtained from Iceland in our lab confirm that the Xenon isotopic composition of the plume source(s) is characterized by lower 136Xe/130Xe ratios than the MORB source and the Iceland plume is more enriched in the Pu-derived Xenon component. These features are interpreted as reflecting different degrees of outgassing and appear not to be the result of preferential recycling of Xenon to the deep mantle. To further investigate how representative the Icelandic measurement...
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