Article
Astronomy & Astrophysics
H. Ernandes, M. J. Castro, B. Barbuy, M. Spite, V Hill, B. Castilho, C. J. Evans
Summary: We examined the abundances of neutron-capture elements in the metal-poor r-process-rich halo star CS 31082-001 with an expanded line list for heavy elements. Using archival near-ultraviolet spectra, we analyzed the abundances and nucleosynthesis of 35 heavy elements. Our results show that the r-process-dominated elements are as enhanced as those in the Sun, but the lighter elements do not follow the solar abundance pattern. Furthermore, we found deficiencies in the abundance of tin and suggest further investigation on the origin and evolution of metal-poor stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
H. Ernandes, B. Barbuy, A. Friaca, V Hill, M. Spite, F. Spite, B. Castilho, C. J. Evans
Summary: The study reveals that the metal-poor star CS 31082-001 is rich in r-process and actinide elements, with the first measurement of uranium abundance in an old star. The abundance estimates of beryllium, vanadium, and copper in CS 31082-001 are presented, showing that beryllium is low due to the cool temperature, while vanadium and copper have comparable abundances to other metal-poor stars. New chemical evolution models are proposed to investigate the results, and the study also explores other atomic lines in the near-ultraviolet for future studies of metal-poor stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
E. J. Snowdon, L. J. A. Scott, C. S. Jeffery, V. M. Woolf
Summary: BPS CS 22940-0009 is a helium-rich B-type star that shares characteristics with both helium-rich B subdwarfs and extreme helium stars. The analysis of its optical spectrum reveals atmospheric parameters and abundance profile consistent with known helium star populations, suggesting that BPS CS 22940-0009 may have formed from the merger of two helium white dwarfs and is currently evolving towards the helium main sequence.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Federico Sestito, Daria Zaremba, Kim A. Venn, Lina D'Aoust, Christian Hayes, Jaclyn Jensen, Julio F. Navarro, Pascale Jablonka, Emma Fernandez-Alvar, Jennifer Glover, Alan W. Mcconnachie, Andre-Nicolas Chene
Summary: Stellar candidates in the extreme outskirts of the Ursa Minor dwarf galaxy have been discovered and confirmed to be part of the galaxy through observations and chemical analysis. The chemical patterns in UMi suggest an outside-in star-formation history and a low star-formation efficiency. Additionally, the analysis of the surface number density profile indicates that UMi's outskirts have been influenced by tidal effects.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Danielle de Brito Silva, Paula Jofre, Douglas Bourbert, Sergey E. Koposov, Jose L. Prieto, Keith Hawkins
Summary: Our study reveals that J01020100-7122208 is a star with a retrograde and highly-eccentric orbit, likely accreted by the Milky Way in the distant past. Its mass and age suggest it is probably an evolved blue straggler.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
T. T. Hansen, J. D. Simon, T. S. Li, A. Frebel, I. Thompson, S. Shectman
Summary: Carbon-enhanced metal-poor (CEMP) stars are important tracers of early Galactic chemical evolution. This study focuses on six CEMP stars in the Carina dSph and compares their abundances to CEMP stars in other dSph galaxies and the Milky Way halo. Detailed elemental abundances were derived through spectroscopic analysis.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Meenakshi Purandardas, Aruna Goswami, J. Shejeelammal, Mayani Sonamben, Ganesh Pawar, David Mkrtichian, Vijayakumar H. Doddamani, Santosh Joshi
Summary: This article presents the results of a high-resolution spectroscopic analysis of a star from the list of carbon stars of LAMOST DR2. The star, named J045, does not exhibit the spectral characteristics of carbon stars and has elemental abundances that closely resemble those found in stars from the Sculptor Dwarf galaxy. Based on these findings, it is suggested that J045 may be an escapee from the Sculptor Dwarf Galaxy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
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
Louise Welsh, Ryan Cooke, Michele Fumagalli
Summary: This study investigates the intrinsic scatter in the chemical abundances of metal-poor Milky Way halo stars and suggests that the most metal-poor stars were enriched by Population III stars. The model used for the enrichment is sensitive to small changes in the stellar sample, particularly in the [Mg/Ca] abundance. The method has the potential to constrain the multiplicity of the first generation of stars but requires a well-understood stellar sample with documented uncertainties associated with nucleosynthetic yields.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
L. Mashonkina, Yu Pakhomov, T. Sitnova, P. Jablonka, S. A. Yakovleva, A. K. Belyaev
Summary: This study presents accurate atmospheric parameters and NLTE abundances for very metal-poor stars in the Sextans dwarf spheroidal galaxy. The stars exhibit alpha-enhancements and a tight relationship between Ba and Mg, suggesting a common origin in massive stars. Additionally, the study reveals a decline in alpha/Fe for stars with higher [Fe/H] values and a distinctive Ba enrichment pattern in one C-enhanced star.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Anastasiya D. Yarovova, Oleg Egorov, Alexei Moiseev, Olga Maryeva
Summary: We discovered an unusual emission-line stellar-like object in the low-metallicity dwarf galaxy NGC 4068, characterized by high velocity dispersion, the presence of He II lambda 4686 angstrom line, and peculiarly low [S II]/[N II] fluxes ratio. Our observations suggest that this object is a single star with high bolometric luminosity surrounded by an expanding nebula. The peculiar nitrogen overabundance in the nebula indicates interaction between the star's ejecta and the interstellar medium, possibly a massive blue supergiant or Wolf-Rayet star.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Tadafumi Matsuno, Helmer H. Koppelman, Amina Helmi, Wako Aoki, Miho N. Ishigaki, Takuma Suda, Zhen Yuan, Kohei Hattori
Summary: This study characterizes the chemical properties of stars from the retrograde kinematic substructure Sequoia. The results show significant differences in chemical abundances between Sequoia and Gaia-Enceladus stars at a lower metallicity, suggesting different influences from type Ia supernovae. The study also confirms the low [Mg/Fe] ratio in Sequoia stars found in previous literature and surveys.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Yutaka Hirai, Timothy C. Beers, Masashi Chiba, Wako Aoki, Derek Shank, Takayuki R. Saitoh, Takashi Okamoto, Junichiro Makino
Summary: Research suggests that most highly r-process-enhanced (RPE) stars are formed in low-mass dwarf galaxies, while stars with higher metallicity may be formed in situ. These findings contribute to our understanding of the assembly history of the Milky Way and the nucleosynthesis of heavy elements.
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
C. Fanelli, L. Origlia, E. Oliva, A. Mucciarelli, N. Sanna, E. Dalessandro, D. Romano
Summary: This study uses high-resolution near-infrared spectroscopy of Arcturus to derive abundances of 26 different chemical species, and introduces a new thermometer and gravitometer for giant stars based on carbon and oxygen abundances comparison. The research also discusses problematic lines in Arcturus spectra that could be affected by deviations from thermal equilibrium and/or chromospheric activity.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Raphael Errani, Julio F. Navarro, Rodrigo Ibata, Nicolas Martin, Zhen Yuan, David S. Aguado, Piercarlo Bonifacio, Elisabetta Caffau, Jonay Gonzalez Hernandez, Khyati Malhan, Ruben Sanchez-Janssen, Federico Sestito, Else Starkenburg, Guillaume F. Thomas, Kim A. Venn
Summary: The C-19 stellar stream is a collection of metal-poor stars in the Milky Way's halo without an obvious progenitor. The stream's width and velocity dispersion are similar to those of disrupted dwarf galaxies, suggesting a different origin than globular clusters. A proposed unconventional model suggests that the C-19 progenitor is a dark matter-dominated system with globular cluster-like abundance patterns, supported by N-body simulations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Piercarlo Bonifacio
Summary: This contribution provides an overview of the study of metal poor stars, with a focus on the efforts to find these rare objects and the need for a comprehensive chemical inventory. It also highlights the unique opportunities offered by CUBES to access abundance indicators in the near-UV region, and encourages the placement of CUBES on a telescope in the northern hemisphere.
EXPERIMENTAL ASTRONOMY
(2023)
Article
Astronomy & Astrophysics
Luca Izzo, Paolo Molaro, Piercarlo Bonifacio, Gabriele Cescutti, Massimo Della Valle, Pierluigi Selvelli
Summary: CUBES is a new high-resolution spectrograph designed for the Very Large Telescope at the European Southern Observatory. It is primarily aimed at studying and characterizing the nucleosynthesis of beryllium. By directly identifying lithium in classical novae and observing the resonance transition of Be-7 II, CUBES can quantify the amount of Be-7 and Li-7 produced by different types of novae in the Milky Way and its nearby satellite galaxies. Additionally, it can provide insights into the properties of nova ejecta, the evolution of shocks in novae, and their connection to high-energy emission observed in these transients.
EXPERIMENTAL ASTRONOMY
(2023)
Article
Astronomy & Astrophysics
Rafael Guerco, Verne V. Smith, Katia Cunha, Sylvia Ekstrom, Carlos Abia, Bertrand Plez, Georges Meynet, Solange Ramirez, Nikos Prantzos, Kris Sellgren, Cristian R. Hayes, Steven R. Majewski
Summary: The chemical abundance analysis of IRS 7 in the nuclear star cluster at the centre of the Milky Way reveals carbon and oxygen depletion, enhanced nitrogen abundance, and derived abundances of other isotopes. This finding provides important clues for studying the process of stellar mixing and confirms the predictions of stellar models.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Nicolas F. Martin, Rodrigo A. Ibata, Else Starkenburg, Zhen Yuan, Khyati Malhan, Michele Bellazzini, Akshara Viswanathan, David Aguado, Anke Arentsen, Piercarlo Bonifacio, Ray Carlberg, Jonay I. Gonzalez Hernandez, Vanessa Hill, Pascale Jablonka, Georges Kordopatis, Carmela Lardo, Alan W. McConnachie, Julio Navarro, Ruben Sanchez-Janssen, Federico Sestito, Guillaume F. Thomas, Kim A. Venn, Sara Vitali, Karina T. Voggel
Summary: This study uses photometric metallicities from the Pristine survey to investigate the existence and determine the metallicities of stellar streams found using the STREAMFINDER algorithm on Gaia Early Data Release 3. All 26 streams in Pristine show clear metallicity distributions, supporting the authenticity of these structures and the effectiveness of STREAMFINDER and Pristine in finding and measuring metallicities. The study identifies six candidate structures with coherent phase-space and metallicity signals that are likely to be stellar streams. Most of the studied streams are very metal-poor, potentially originating from low-luminosity dwarf galaxies or globular clusters with significantly lower metallicity than any known Milky Way globular cluster. The study highlights the importance of high-quality photometric metallicities in utilizing Gaia data for Galactic Archeology studies, enabling a closer examination of the early stages of our Galaxy's formation and its stellar halo constituents.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
P. Molaro, L. Izzo, P. Selvelli, P. Bonifacio, E. Aydi, G. Cescutti, E. Guido, E. J. Harvey, M. Hernanz, M. Della Valle
Summary: The recurrent nova RS Oph had a new outburst in August 8, 2021, with a visible brightness of V = 4.8 mag. Observations of the outburst detected the presence of Be-7, possibly formed in thermonuclear runaway reactions. The estimated Be-7 yield was N(Be-7)/N(H) = 5.7 x 10(-6), which is among the lowest measured in classical novae. The detection of Be-7 in RS Oph supports the idea that novae are the main source of Li-7 in the Galaxy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
D. S. Aguado, E. Caffau, P. Molaro, C. Allende Prieto, P. Bonifacio, J. I. Gonzalez Hernandez, R. Rebolo, S. Salvadori, M. R. Zapatero Osorio, S. Cristiani, F. Pepe, N. C. Santos, G. Cupani, P. Di Marcantonio, V. D'Odorico, C. Lovis, N. J. Nunes, C. J. A. P. Martins, D. Milakovic, J. Rodrigues, T. M. Schmidt, A. Sozzetti, A. Suarez Mascareno
Summary: This article presents the characteristics and observational results of the carbon-enhanced metal-poor (CEMP) star SMSS J160540.18-144323.1, confirming its chemically unmixed nature and the lack of mass transfer from a binary companion based on the analysis of its radial velocity and isotopic ratio.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
F. Lucertini, L. Monaco, E. Caffau, A. Mucciarelli, S. Villanova, P. Bonifacio, L. Sbordone
Summary: This study investigates the sulfur content of Ruprecht 106 globular cluster and Trumpler 5 open cluster. The results show that Ruprecht 106 has lower sulfur content and supports its extra-galactic origin, while Trumpler 5 follows the trend of the Galactic disk in terms of sulfur abundance.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
D. S. Aguado, S. Salvadori, A. Skuladottir, E. Caffau, P. Bonifacio, I Vanni, V Gelli, I Koutsouridou, A. M. Amarsi
Summary: In this study, a new method called PISN-explorer was proposed to identify stars with dominant PISN enrichment. Through analyzing data from large spectroscopic surveys, the researchers built a catalog with 166 candidates of PISN descendants and found a candidate with a complete chemical signature. High-resolution observations are needed to confirm the selected candidates.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Francois Hammer, Hefan Li, Gary A. Mamon, Marcel S. Pawlowski, Piercarlo Bonifacio, Yongjun Jiao, Haifeng Wang, Jianling Wang, Yanbin Yang
Summary: Halo inhabitants in the Milky Way include individual stars, stellar streams, star, and globular clusters, and dwarf galaxies. The study compares globular clusters and dwarf galaxies, finding that their half-light radius is related to their orbital pericentre and total energy. The study also suggests that the accretion epoch of stellar systems in the Milky Way halo can be calibrated by the total orbital energy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Physics, Applied
Faouzi Boussaha, Jie Hu, Paul Nicaise, Jean-Marc Martin, Christine Chaumont, Pham Viet Dung, Josiane Firminy, Florent Reix, Piercarlo Bonifacio, Michel Piat, Herve Geoffray
Summary: We demonstrate the single photon counting mode at 405 and 850 nm with stoichiometric TiN-based microwave kinetic inductance detectors realized on a sapphire substrate and operated at bath temperatures over 300 mK. The detectors use single 15-25 nm-thick TiN layers featuring a critical temperature in the 2-3 K range. We found that the energy-resolving power R = E/Delta E exhibits an optimum with bath temperature, occurring in the 300-450 mK range, which can be almost double compared to those obtained at the lowest temperatures. Furthermore, the single photon regime is observed up to 700 mK. In addition to a high-temperature operation, the single stoichiometric layer would allow achieving a better uniformity in the critical temperature and, thus, kinetic inductance, compared to the often desired similar to 1 K sub-stoichiometric TiN.
APPLIED PHYSICS LETTERS
(2023)
Article
Astronomy & Astrophysics
E. J. Harvey, E. Aydi, L. Izzo, C. Morisset, M. J. Darnley, K. Fitzgerald, P. Molaro, F. Murphy-Glaysher, M. P. Redman, M. Shrestha
Summary: V906 Carinae is one of the best observed novae recently, with prolific dust production and shocks in the early ejecta outflow. This study examines the consequences of these early interactions through high-resolution Ultraviolet and Visual Echelle spectrograph spectroscopy, and investigates the formation of the final structure through extrapolation. The geometry and shaping history of the shell structure are analyzed using a spectral line SHAPE model fit, and spectral tracers of shocks and ionized environment are examined. Temperature, density, and abundance analyses of the evolving nova shell are presented.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Linda Lombardo, Piercarlo Bonifacio, Elisabetta Caffau, Patrick Francois, Pascale Jablonka, Georges Kordopatis, Nicolas Martin, Else Starkenburg, Zhen Yuan, Luca Sbordone, Federico Sestito, Vanessa Hill, Kim Venn
Summary: In this paper, the authors studied high-resolution spectra of 19 stars with metallicity estimates below -3.5 and used metallicity-sensitive photometric indices based on Pristine photometry. They aimed to understand the characteristics of stars in this parameter space, especially extremely metal-poor stars, and investigate possible contaminants for future studies. The results showed that the sample of extreme stars was heavily contaminated by variable stars, particularly short period eclipsing binaries. Serendipitously, they discovered eight double-lined spectroscopic eclipsing binaries, which could be further studied to determine their masses and distances. They also identified two stars with metallicity below -3.0, one of which may belong to the Gaia-Sausage-Enceladus structure. The investigation highlighted the importance of removing photometrically variable stars when selecting truly metal-poor stars, and suggested that Gaia photometry can effectively remove about 85% of such stars. Additionally, the study demonstrated the potential of Pristine photometry in discovering double-lined spectroscopic binaries among short period eclipsing binaries.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Paolo Molaro, Federico Bernardini
Summary: Chisel marks found on a stone in the Rupinpiccolo hill fort in northeastern Italy are suggested to represent the night sky. Analysis shows that some of these marks correspond to popular stellar asterisms, indicating intentional representation. The high correlation between these marks and stellar positions suggests ancient observations and recording of constellations. However, the identity of one mark remains unknown.
ASTRONOMISCHE NACHRICHTEN
(2023)