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
C. Aguilera-Gomez, L. Monaco, A. Mucciarelli, M. Salaris, S. Villanova, E. Pancino
Summary: This study examines the initial lithium content of lower red giant branch stars in globular clusters and compares it to cosmological predictions. The results show a plateau in the lithium abundance, with no correlation with metallicity. Additionally, a Li-rich giant star is discovered in one of the clusters, possibly due to pollution from external sources.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
G. Cescutti, C. Morossi, M. Franchini, P. Di Marcantonio, C. Chiappini, M. Steffen, M. Valentini, P. Francois, N. Christlieb, C. Cortes, C. Kobayashi, E. Depagne
Summary: Researchers analyzed the barium lines in two halo stars, HD 6268 and HD 4306, finding that the former showed an s-process composition while the latter displayed an r-process isotopic pattern. This confirms the theoretical expectation that both r-process events and s-process contribution by rotating massive stars have affected the ancient halo of our Galaxy.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Collin L. Kielty, Kim A. Venn, Federico Sestito, Else Starkenburg, Nicolas F. Martin, David S. Aguado, Anke Arentsen, Sebastien Fabbro, Jonay I. Gonzalez Hernandez, Vanessa Hill, Pascale Jablonka, Carmela Lardo, Lyudmila Mashonkina, Julio F. Navarro, Chris Sneden, Guillaume F. Thomas, Kris Youakim, Spencer Bialek, Ruben Sanchez-Janssen
Summary: High-resolution optical spectra of 30 metal-poor stars from the Pristine survey were analyzed using the GRACES spectrograph at the Gemini Observatory. The study revealed that most of these stars exhibit chemical compositions similar to other extremely metal-poor stars in the Galactic halo, but also show some unusual chemical features, providing insights into the formation and early chemical evolution of the Galaxy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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
M. P. Roriz, M. Lugaro, C. B. Pereira, C. Sneden, S. Junqueira, A. Karakas, N. A. Drake
Summary: A new study presents elemental abundances for neutron-capture elements in 180 barium giant stars, revealing discrepancies in La abundances compared to previous literature. The data set shows an overabundance of neutron-capture elements in these stars, but behaves similarly to field stars in some aspects. While model predictions match observations in certain ratios, discrepancies are found in other ratios, requiring further investigation into neutron capture models.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Physics, Multidisciplinary
Basudeb Dasgupta, Ranjan Laha, Anupam Ray
Summary: The discovery of unusual masses of black holes by gravitational wave experiments raises fundamental questions about their origin. A proposed new channel for the production of low mass black holes involves the catastrophic accretion of nonannihilating dark matter by stellar objects. Testing methods are suggested, focusing on the redshift dependence of the merger rate as a probe of the transmuted origin of low mass black holes.
PHYSICAL REVIEW LETTERS
(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
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
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
J. Schiappacasse-Ulloa, Sara Lucatello, M. J. Rain, Adriano Pietrinferni
Summary: This paper presents a chemical abundance analysis of 217 stars in the metal-poor globular cluster NGC 6752 and explores the characteristics and correlations of stars with high aluminum and lithium content.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
R. Zhang, S. Lucatello, A. Bragaglia, J. Alonso-Santiago, G. Andreuzzi, G. Casali, R. Carrera, E. Carretta, V. D'Orazi, A. Frasca, X. Fu, L. Magrini, I Minchev, L. Origlia, L. Spina, A. Vallenari
Summary: This study investigates giant stars in 18 OCs using high-resolution spectra and provides comprehensive chemical characterization for 16 OCs for the first time. Results show the behavior of lithium, sodium, and aluminum in stellar evolution and variations in abundance ratios in terms of radial, vertical, and age trends. Additionally, a comparison with models reveals the characteristics of O and Mg abundance ratios at different ages.
ASTRONOMY & ASTROPHYSICS
(2022)
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
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)