Andre Sieverding

Max Planck Institute for Astrophysics | MPA · Division of Stellar physics

We present a new nucleosynthesis process that may take place on neutron-rich ejecta experiencing an intensive neutrino flux. The nucleosynthesis proceeds similarly to the standard $r$-process, a sequence of neutron-captures and beta-decays, however with charged-current neutrino absorption reactions on nuclei operating much faster than beta-decays....

We compare the core-collapse evolution of a pair of 15.8 M ☉ stars with significantly different internal structures, a consequence of the bimodal variability exhibited by massive stars during their late evolutionary stages. The 15.78 and 15.79 M ☉ progenitors have core masses (masses interior to an entropy of 4 k B baryon ⁻¹ ) of 1.47 and 1.78 M ☉...

After decades, the theoretical study of core-collapse supernova explosions is moving from parameterized, spherically symmetric models to increasingly realistic multi-dimensional simulations. Obtaining nucleosynthesis yields based on such multi-dimensional core-collapse supernova (CCSN) simulations, however, is not straightforward and frequently tra...

We compare the core-collapse evolution of a pair of 15.8 $M_\odot$ stars with significantly different internal structures, a consequence of bimodal variability exhibited by massive stars during their late evolutionary stages. The 15.78 and 15.79 $M_\odot $ progenitors have core masses of 1.47 and 1.78 $M_\odot$ and compactness parameters $\xi_{1.75...

The radioisotope 26Al is a key observable for nucleosynthesis in the Galaxy and the environment of the early Solar System. To properly interpret the large variety of astronomical and meteoritic data, it is crucial to understand both the nuclear reactions involved in the production of 26Al in the relevant stellar sites and the physics of such sites....

Evidence for the presence of short-lived radioactive isotopes when the Solar System formed is preserved in meteorites, providing insights into the conditions at the birth of our Sun. A low-mass core-collapse supernova had been postulated as a candidate for the origin of Be10, reinforcing the idea that a supernova triggered the formation of the Sola...

Evidence for the presence of short-lived radioactive isotopes when the Solar System formed is preserved in meteorites, providing insights into the conditions at the birth of our Sun. A low-mass core-collapse supernova had been postulated as a candidate for the origin of $^{10}$Be, reinforcing the idea that a supernova triggered the formation of the...

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 ⁵⁴ Cr among materials formed in different regions of the protoplanetary disk has been attributed to variable amounts of presolar, chromium-rich oxide (chromite) grains,...

Isotope variations of nucleosynthetic origin among Solar System's solid samples are well documented, yet the origin of these variations is still uncertain. The observed variability of \iso{54}Cr among materials formed in different regions of the proto-planetary disk has been attributed to variable amounts of presolar chromium-rich oxide (chromite)...

problem but they are key to understand the chemical composition of the solar system. Self-consistent, numerical simulations of supernova explosions have made great progress in the last decade and I am going to show results from nucleosynthesis calculations based on a self-consistent, three-dimensional supernova simulation and highlight thechallenge...

The cosmic evolution of the chemical elements from the Big Bang to the present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle of matter recurrently re-processes metal-enriched stellar ejecta into the next generation of stars. The study of cosmic nucleosynthesis and of this matter cycle requires the understan...

We study the effects of additional cooling due to the emission of a dark matter candidate particle, the dark photon, on the final phases of the evolution of a 15 Me star and resulting modifications of the pre-supernova neutrino signal. For a substantial portion of the dark photon parameter space the extra cooling speeds up Si burning, which results...

The discrepancy between observations from γ-ray astronomy of the Fe60/Al26 γ-ray flux ratio and recent calculations is an unresolved puzzle in nuclear astrophysics. The stellar β-decay rate of Fe59 is one of the major nuclear uncertainties impeding us from a precise prediction. The important Gamow-Teller strengths from the low-lying states in Fe59...

We study the effects of additional cooling due to the emission of a dark matter candidate particle, the dark photon, on the final phases of the evolution of a $15\,M_\odot$ star and resulting modifications of the pre-supernova neutrino signal. For a substantial portion of the dark photon parameter space the extra cooling speeds up Si burning, which...

The cosmic evolution of the chemical elements from the Big Bang to the present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle of matter recurrently re-processes metal-enriched stellar ejecta into the next generation of stars. The study of cosmic nucleosynthesis and this matter cycle requires the understandin...

Based on a 3D supernova simulation of an 11.8 M⊙ progenitor model with an initial solar composition, we study the nucleosynthesis using tracers covering the innermost 0.1 M⊙ of the ejecta. These ejecta are mostly proton-rich and contribute significant amounts of 45Sc and 64Zn. The production of heavier isotopes is sensitive to the electron fraction...

Neutrino reactions on nuclei play important roles for the dynamics of supernovae and their associated nucleosynthesis. This manuscript summarizes the current status in deriving the relevant cross sections for supernova neutrinos and discusses the importance of neutrino-nucleus reactions for supernova nucleosynthesis. In particular we report on the...

Based on a 3D supernova simulation of an $11.8\,M_\odot$ progenitor model with initial solar composition, we study the nucleosynthesis using tracers covering the innermost $0.1\,M_\odot$ of the ejecta. These ejecta are mostly proton-rich and contribute significant amounts of $^{45}$Sc and $^{64}$Zn. The production of heavier isotopes is sensitive t...

The wind driven by the intense neutrino emission from a protoneutron star (PNS) is an important site for producing nuclei heavier than the Fe group. Because of certain features in the neutrino angular distributions, the so-called fast flavor oscillations may occur very close to the PNS surface, effectively resetting the neutrino luminosities and en...

We present a study of nucleosynthesis for conditions of high Ye outflows from NeutronStar Mergers (NSMs). We investigate the effect of new beta-decay rates measurements and uncertaintiesin nuclear masses of the newly measured 84,85 Ga to the r-process nucleosynthesis calculations. The impactof these quantities to the production of the elements of t...

We report mass measurements of neutron-rich Ga isotopes Ga80−85 with TRIUMF's Ion Trap for Atomic and Nuclear science. The measurements determine the masses of Ga80−83 in good agreement with previous measurements. The masses of Ga84 and Ga85 were measured for the first time. Uncertainties between 25 and 48 keV were reached. The new mass values redu...

We calculate the rate of production of dark photons from electron-positron pair annihilation in hot and dense matter characteristics of supernova progenitors. Given the nonlinear dependence of the emission rate on the dark photon mass and current astrophysical constraints on the dark photon parameter space, we focus on the mass range of 1–10 MeV. F...

The neutrino process that occurs in the outer stellar shells during a supernova explosion and involves neutrino–nucleus reactions produces a range of rare, stable, and radioactive isotopes. We improve previous ν-process studies by using, for the first time, the time-dependent neutrino emission spectra, as predicted from supernova simulations, rathe...

We calculate the rate of production of dark photons from electron-positron pair annihilation in hot and dense matter characteristic of supernova progenitors. Given the non-linear dependence of the emission rate on the dark photon mass and current astrophysical constraints on the dark photon parameter space, we focus on the mass range of 1--10 MeV....

The neutrino process that occurs in the outer stellar shells during a supernova explosion and involves neutrino-nucleus reactions produces a range of rare, stable and radioactive isotopes. We improve previous $\nu$-process studies by using, for the first time, the time-dependent neutrino emission spectra, as predicted from supernova simulations, ra...

Neutrinos produced during a supernova explosion induce reactions on abundant nuclei in the outer stellar shells and contribute in this way to the synthesis of the elements in the Universe. This neutrino nucleosynthesis process has been identified as an important contributor to the origin of $^7$Li, $^{11}$B,$^{19}$F, $^{138}$La, and $^{180}$Ta, but...

We report mass measurements of neutron-rich Ga isotopes in the A $\approx$ 84 region crossing the N=50 neutron shell closure with TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The measurements, employing a multiple-reflection time-of-flight mass spectrometer, determine the masses of $^{80-85}$Ga with uncertainties between $25-48$~keV; t...

We study the neutrino-induced production of nuclides in explosive supernova nucleosynthesis for progenitor stars with solar metallicity including neutrino-nucleus reactions for all nuclei with charge numbers Z < 76, with average neutrino energies in agreement with modern supernova simulations. Considering progenitors with initial main sequence mass...

We study the neutrino-induced production of nuclides in explosive supernova nucleosynthesis for progenitor stars with solar metallicity including neutrino nucleus reactions for all nuclei with charge numbers $Z < 76$ with average neutrino energies in agreement with modern Supernova simulations. Considering progenitors with initial main sequence mas...

Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of $^{82}$Zr and $^{84}$Nb were measured for the first time with an uncertainty of $\sim 10$ keV, and the masses of $^{79}$Y, $^{81}$Zr, and $^{83}$Nb were re-determined with a higher precision. %The latter differ significantly from their literature val...

The neutrino-induced nucleosynthesis (v process) in supernova explosions of massive stars of solar metallicity with initial main sequence masses between 15 and 40 M⨀ has been studied. A new extensive set of neutrino-nucleus cross-sections for all the nuclei included in the reaction network is used and the average neutrino energies are reduced to ag...

The neutrino-induced nucleosynthesis (ν process) in supernova explosions of massive stars of solar metallicity with initial main sequence masses between 13 and 30 M⊙ has been studied with an analytic explosion model using a new extensive set of neutrino-nucleus cross-sections and spectral properties that agree with modern supernova simulations. The...

Core-collapse supernovae liberate an energy equivalent to the binding energy of the newly formed neutron star by emitting ∼ 1058 neutrinos of all flavors with typical energies of ∼ 10 MeV. These neutrinos are responsible for a matter outflow from the proto-neutron star known as the neutrino-driven wind. The nucleosynthesis in the wind is very sensi...

The neutrino-induced nucleosynthesis (ν process) in supernova explosions of massive stars of solar metallicity with initial main sequence masses between 15 and 40 M⊙ has been studied. A new extensive set of neutrino-nucleus cross-sections for all the nuclei included in the reaction network is used and the average neutrino energies are reduced to ag...

We study the neutrino-induced production of nuclides in explosive supernova nucleosynthesis for progenitor stars with solar metallicity and initial main sequence masses between 15 M$_\odot$ and 40 M$_\odot$. We improve previous investigations i) by using a global set of partial differential cross sections for neutrino-induced charged- and neutral-c...