Article
Astronomy & Astrophysics
M. P. Roriz, C. B. Pereira, S. Junqueira, M. Lugaro, N. A. Drake, C. Sneden
Summary: We present detailed chemical compositions of four chemically peculiar stars on the first-ascent red giant branch, which lack high spectral resolution comprehensive analyses. These stars, BD+03 degrees 2688, HE 0457-1805, HE 1255-2324, and HE 2207-1746, exhibit a range in Galactic population membership with metallicities of [Fe/H] = -1.21, -0.19, -0.31, and -0.55, respectively. We obtained elemental abundances for 28 elements, including CNO group and C-12/C-13 ratios, as well as novel results for the heavy elements tungsten and thallium. All four stars show significant enhancements of neutron-capture elements, indicating enrichments from the slow neutron capture (s-process).
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Umberto Battino, Claudia Lederer-Woods, Marco Pignatari, Benjamin Soos, Maria Lugaro, Diego Vescovi, Sergio Cristallo, Philip J. Woods, Amanda Karakas
Summary: This study re-evaluates the production of Al-26 and its impact on stellar nucleosynthesis. The new reactivities have a significant effect on both low- and high-mass stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
M. P. Roriz, M. Lugaro, C. B. Pereira, N. A. Drake, S. Junqueira, C. Sneden
Summary: Barium (Ba) stars show atmospheric signs of the slow neutron-capture mechanism from asymptotic giant branch (AGB) stars, with rubidium (Rb) playing a key role in the s-process diagnostic. The study of 180 Ba stars reveals that Rb abundances are consistent with s-process models from low-mass AGB stars, indicating the main neutron source is the C-13(alpha,n)O-16 reaction in the companions of these Ba stars. Former IR/OH massive AGB star companions were not found in this study.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
C. Abia, P. de Laverny, S. Korotin, A. Asensio Ramos, A. Recio-Blanco, N. Prantzos
Summary: By analyzing the Rb and Zr abundances in KM-type giant stars, it was found that there is a Rb deficiency in giant stars, but once NLTE corrections are performed, the ratios are very close to solar values. This contrasts with the Rb deficiency found in M dwarfs, indicating potential differences in nucleosynthesis mechanisms for different types of stars.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
D. A. Baiko
Summary: This study focuses on the nuclear fusion reactions in white dwarfs and neutron stars, and calculates the plasma screening factor from first principles. It finds good agreement with earlier results and identifies a deviation in reaction rates that can be approximated by a simple analytic expression. The method developed in this study can be extended to ion mixtures and crystallized phases of stellar matter.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Ben T. Pepper, A. G. Istrate, A. D. Romero, S. O. Kepler
Summary: One of the largest uncertainties in stellar evolutionary computations is the accuracy of the considered reaction rates. This study investigates the impact of uncertainties in the C-12(alpha, gamma)O-16 reaction rates on the evolution of white dwarfs and their progenitors. The results show that the considered reaction rates have significant effects on various stages of stellar evolution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Thomas Lawson, Marco Pignatari, Richard J. Stancliffe, Jacqueline den Hartogh, Sam Jones, Chris L. Fryer, Brad K. Gibson, Maria Lugaro
Summary: This study examines the impact of core-collapse supernovae on the production of short-lived radioactive isotopes and finds that explosion energy and remnant mass play crucial roles in determining the final yields of these isotopes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jordan Schofield, Marco Pignatari, Richard J. Stancliffe, Peter Hoppe
Summary: In this study, isotopic abundances of C, N, Al, Si, and Ti measured in presolar grains were compared with predictions from 21 CCSN models. The research found that high energy models favor the formation of a C/Si zone enriched in C-12, Si-28, and Ti-44.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
L. Cavallo, G. Cescutti, F. Matteucci
Summary: In this paper, the authors investigate the origin of the large star-to-star variation in the [Eu/Fe] ratios in extremely metal-poor stars. By considering the chemical enrichment of Eu in the building blocks of the Galactic halo, they find that the dynamics of binary systems in the gravitational potential of the host galaxy play a role in the enrichment from neutron star mergers.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Maren Brauner, Thomas Masseron, Domingo A. Garcia-Hernandez, Marco Pignatari, Kate A. Womack, Maria Lugaro, Christian R. Hayes
Summary: The origin of phosphorus, an essential element for life on Earth, is currently unknown. The discovery of phosphorus-rich and metal-poor giants challenges current theories on stellar nucleosynthesis and calls for a search of their progenitor or polluter. By studying a larger sample of phosphorus-rich stars, researchers aim to find a reliable chemical abundance pattern that defines these peculiar stars and contribute to the search for the source of phosphorus in our Galaxy.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
A. Choplin, S. Goriely, R. Hirschi, N. Tominaga, G. Meynet
Summary: The study investigates the mechanism of p-process nucleosynthesis in rotating massive stars and finds that rotation has a comparable impact on the p-process as on the s-process. The contribution of core-collapse supernovae from massive stars to the solar p-nuclei may have been underestimated in the past.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Pavel A. Denissenkov, Falk Herwig, Georgios Perdikakis, Hendrik Schatz
Summary: This study investigates the impact of (n,gamma) reaction rate uncertainties on the predicted abundances of neutron-capture elements in carbon-enhanced metal-poor stars, finding that certain reactions have significant effects on the predicted abundances of barium and praseodymium.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Pavel A. Denissenkov, Chris Ruiz, Sriteja Upadhyayula, Falk Herwig
Summary: Recent spectroscopic measurements reveal high abundances of Be-7 in nova ejecta, deviating from theoretical predictions, but the assumption of enhanced He-4 abundances helps reduce this discrepancy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
E. Monpribat, S. Martinet, S. Courtin, M. Heine, S. Ekstrom, D. G. Jenkins, A. Choplin, P. Adsley, D. Curien, M. Moukaddam, J. Nippert, S. Tsiatsiou, G. Meynet
Summary: This study provides new numerical tables for C-12 + C-12 reaction rates and associated uncertainty estimations, along with analytical formulae that can be directly implemented into stellar evolution codes. The impact of these new rates on C-burning in stars was investigated, showing differences in central temperatures and burning lifetimes.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
M. Deal, C. J. A. P. Martins
Summary: The success of primordial nucleosynthesis has been limited by the long-standing lithium problem. A self-consistent perturbative analysis is used to explore the problem and its possible solutions in the context of the latest observations and theoretical modeling. The research concludes that the lithium problem most likely has an astrophysical solution, while the Deuterium discrepancy provides a possible indication of new physics.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Thomas C. L. Trueman, Benoit Cote, Andres Yague Lopez, Jacqueline den Hartogh, Marco Pignatari, Benjamin Soos, Amanda Karakas, Maria Lugaro
Summary: Analysis of inclusions in primitive meteorites reveals the existence of short-lived radionuclides with half-lives of 0.1-100 Myr in the early solar system. This study investigates the origin of these radionuclides and their formation in the early solar system using galactic chemical evolution modeling.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Stephanie Monty, David Yong, Anna F. Marino, Amanda Karakas, Madeleine McKenzie, Frank Grundahl, Aldo Mura-Guzman
Summary: Using differential abundance analysis, this study reveals the presence of multiple chemical peculiarities in the globular clusters NGC 288 and NGC 362. The measurements of 20 elements showed differential uncertainties ranging from 0.01 to 0.02 dex in both clusters. The analysis found dispersion in the abundances of various elements in both clusters, with NGC 362 demonstrating additional dispersion in some elements.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Kate A. Womack, Fiorenzo Vincenzo, Brad K. Gibson, Benoit Cote, Marco Pignatari, Hannah E. Brinkman, Paolo Ventura, Amanda Karakas
Summary: By comparing chemical evolution models to observations of fluorine abundances in Milky Way stars, researchers have identified the significant impact of rotational velocity of massive stars on the chemical evolution of fluorine. They also predict the importance of metal-rich stars, such as pollution stars, in the evolution of fluorine.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
D. Kamath, F. Dell'Agli, P. Ventura, H. Van Winckel, S. Tosi, A. Karakas
Summary: We study a sample of single Galactic post-AGB stars to determine their initial masses, chemical compositions, and progenitor ages. The luminosity and surface carbon abundance prove to be the most valuable indicators of the star's previous evolution and nucleosynthetic history. This allows us to classify the post-AGB sample into different classes based on their evolutionary history on the AGB. The analysis sheds new light on debated issues related to AGB evolution and nucleosynthesis.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
M. P. Roriz, C. B. Pereira, S. Junqueira, M. Lugaro, N. A. Drake, C. Sneden
Summary: We present detailed chemical compositions of four chemically peculiar stars on the first-ascent red giant branch, which lack high spectral resolution comprehensive analyses. These stars, BD+03 degrees 2688, HE 0457-1805, HE 1255-2324, and HE 2207-1746, exhibit a range in Galactic population membership with metallicities of [Fe/H] = -1.21, -0.19, -0.31, and -0.55, respectively. We obtained elemental abundances for 28 elements, including CNO group and C-12/C-13 ratios, as well as novel results for the heavy elements tungsten and thallium. All four stars show significant enhancements of neutron-capture elements, indicating enrichments from the slow neutron capture (s-process).
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
L. Mashonkina, A. Arentsen, D. S. Aguado, A. Smogorzhevskii, M. Hampel, A. Karakas, F. Sestito, N. F. Martin, K. A. Venn, J. I. Gonzalez Hernandez
Summary: This study presents high-resolution spectroscopic follow-up of the carbon-enhanced metal-poor star Pristine 184237. The atmospheric parameters and abundances for 32 elements were determined, revealing unique element abundance patterns. It is the first star of the CEMP-r/s subclass identified in the inner Galaxy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Stephanie Monty, David Yong, Davide Massari, Madeleine McKenzie, GyuChul Myeong, Sven Buder, Amanda Karakas, Ken C. Freeman, Anna F. Marino, Vasily Belokurov, N. Wyn Evans
Summary: By comparing the chemical abundances of globular clusters NGC 362 and NGC 288, we find strong similarities between them but marked differences when compared to the Gaia-Sausage-Enceladus (GSE) stars. This suggests that NGC 362 and NGC 288 are either not galactic siblings or that GSE had enough chemical inhomogeneity to produce two similar yet distinct clusters with different chemistry compared to constituent stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Boquan Chen, Michael R. Hayden, Sanjib Sharma, Joss Bland-Hawthorn, Chiaki Kobayashi, Amanda Karakas
Summary: We propose a multizone galactic chemical evolution model that considers the most recently updated nucleosynthesis yields. The model incorporates physical processes such as gas feedback, radial flow of gas, infall of fresh gas, and radial migration. We analyze the impact of these processes on the observed properties of the Milky Way. The model successfully reproduces the observed distribution of stars in terms of metallicity and alpha-to-iron ratio.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Tuila Ziliotto, Antonino Milone, Anna F. F. Marino, Aaron L. L. Dotter, Alvio Renzini, Enrico Vesperini, Amanda Karakas, Giacomo Cordoni, Emanuele Dondoglio, Maria V. V. Legnardi, Edoardo P. P. Lagioia, Anjana Mohandasan, Sarah Baimukhametova
Summary: Recent studies have shown the theoretical behavior of multiple populations in metal-intermediate globular clusters using the JWST. These findings are supported by observations of multiple populations in M dwarfs. In this study, the authors explore multiple populations in metal-poor GCs and identify distinct stellar populations using synthetic spectra and isochrones. The researchers find that the helium abundances of second-generation stars are higher than those of the first generation, and that the color-magnitude diagram shows a wide color broadening due to multiple populations.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Giulia C. Cinquegrana, Meridith Joyce, Amanda Karakas
Summary: The study investigates the minimum mass required for a star to undergo an Fe core collapse supernova in super metal-rich models. It is found that the minimum initial mass for Fe core collapse is lower in super metal-rich models compared to solar metallicity. This has implications for accurately modeling supernovae rates as a function of metallicity in galactic chemical evolution simulations, particularly for metal-rich spiral and elliptical galaxies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Jianhui Lian, Nicholas Storm, Guillaume Guiglion, Aldo Serenelli, Benoit Cote, Amanda Karakas, Nicholas Boardman, Maria Bergemann
Summary: By studying the chemical abundances of stars, the locations of neutron capture processes have been investigated. For r-process elements, the distribution of the ratio of Europium to Iron suggests a short delay time of the site that produces Europium, but other independent observations suggest a significant fraction of long delayed neutron star mergers. Including short delayed r-process sites can resolve this inconsistency. For s-process elements, the ratio of Barium to Yttrium shows weak metallicity dependence, suggesting that the s-process efficiency of low-mass AGB stars in current models may be overestimated.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
David Yong, Fan Liu, Yuan-Sen Ting, Meridith Joyce, Bertram Bitsch, Fei Dai, Aaron Dotter, Amanda I. Karakas, Michael T. Murphy
Summary: This study conducts a line-by-line differential analysis of 125 co-moving pairs of stars and obtains high-precision stellar parameters. These stars are classified into chemically homogeneous and inhomogeneous groups. The study reveals the relationship between separation, effective temperature, and chemically homogeneous pairs. The importance of this study lies in the discovery of a sample of bright co-moving pairs with chemical abundance differences comparable to that of the Hyades open cluster, which can be used for calibrating stellar abundances in large-scale spectroscopic surveys.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Zara Osborn, Amanda Karakas, Alex J. Kemp, Robert G. Izzard
Summary: In this study, the impact of binary evolution on Al-26 yields is explored. It is found that the key condition for achieving the most overproduction of Al-26 is for stars to have small cores relative to their total masses when entering the TP-AGB phase. The population with a binary fraction of 0.75 shows a 25% increase in Al-26 weighted population yield compared to the population of single-stars only. Further analysis of the stellar interior structure supports these results.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. F. Marino, A. P. Milone, E. Dondoglio, A. Renzini, G. Cordoni, H. Jerjen, A. Karakas, E. P. Lagioia, M. V. Legnardi, M. McKenzie, A. Mohandasan, M. Tailo, D. Yong, T. Ziliotto
Summary: Chromosome maps of globular clusters reveal the inhomogeneity of metallicity in these ancient structures. Type II clusters show larger variations, possibly due to multiple generations of stars. Most clusters also have inhomogeneous first generation stars, pointing towards a not fully mixed molecular cloud.
ASTROPHYSICAL JOURNAL
(2023)