Article
Astronomy & Astrophysics
Partha Pratim Goswami, Aruna Goswami
Summary: Understanding the chemical composition of CEMP stars with enhanced heavy element abundances remains problematic. In this study, we analyzed the carbon-enhanced extremely metal-poor object HE 1005-1439 and found a unique surface chemical composition that is influenced by both s-process and i-process nucleosynthesis. The observed abundance pattern cannot be explained by theoretical s-process models, but our parametric-model-based analysis suggests contributions from both s- and i-process. We propose a formation scenario involving proton ingestion episodes followed by s-process AGB nucleosynthesis in a now extinct companion AGB star.
ASTRONOMY & ASTROPHYSICS
(2022)
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
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
T. Ryabchikova, S. Zvyagintsev, A. Tkachenko, V Tsymbal, Yu Pakhomov, E. Semenko
Summary: The study on the SB2 system HD 60803 involved a detailed spectroscopic analysis using different methods to determine the fundamental parameters of the components, revealing consistent results. While the chemical composition of the components showed no significant difference, the abundance of lithium exhibited a slight variance. The estimated age of the system was concluded to be 5.5 +/- 0.5 billion years.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Linda Lombardo, Patrick Francois, Piercarlo Bonifacio, Elisabetta Caffau, Aroa del Mar Matas Pinto, Corinne Charbonnel, Georges Meynet, Lorenzo Monaco, Gabriele Cescutti, Alessio Mucciarelli
Summary: Through the study of 26 young metal-rich giants, conclusions were drawn from their chemical composition and rotational velocities to provide an opportunity for comparison with predictions from stellar evolution models. All sample stars are in prograde motion around the Galactic centre, with most having low [C/Fe] and high [N/Fe] ratios, indicating they have undergone CNO processing and first dredge-up.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
B. Seli, K. Olah, L. Kriskovics, Zs Kovari, K. Vida, L. G. Balazs, J. M. Laming, L. van Driel-Gesztelyi, D. Baker
Summary: The different elemental abundances of the photosphere and the corona in the Sun and other stars are influenced by the first ionisation potential (FIP) effect, which is characterized by the FIP bias. This study investigates the relationship between the surface temperature of stars and the FIP bias, as well as the influence of other astrophysical parameters. The results show that there are new features in the T-eff-FIP bias diagram, and the FIP bias is influenced by stellar activity indicators and other parameters. The study also identifies three clusters in the FIP bias determinant parameter space.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
R. Razera, B. Barbuy, T. C. Moura, H. Ernandes, A. Perez-Villegas, S. O. Souza, C. Chiappini, A. B. A. Queiroz, F. Anders, J. G. Fernandez-Trincado, A. C. S. Friaca, K. Cunha, V. V. Smith, B. X. Santiago, R. P. Schiavon, M. Valentini, D. Minniti, M. Schultheis, D. Geisler, J. Sobeck, V. M. Placco, M. Zoccali
Summary: This article discusses the different stellar populations in the central part of the Galaxy and analyzes the abundances of 58 candidate stars belonging to the spheroidal bulge. The results show that these stars have normal alpha-element enhancements in oxygen, magnesium, silicon, and calcium abundances, suggesting they are not accreted debris. The nitrogen abundances show no spread, indicating that these stars are not second generation stars from globular clusters. However, the sample stars show enhancement in cerium, which suggests an s-process origin.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Adam T. Knowles, A. E. Sansom, C. Allende Prieto, A. Vazdekis
Summary: This paper introduces a new semi-empirical stellar spectra library based on the empirical MILES library, with a new high-resolution theoretical stellar spectra library specifically designed for stellar population studies. The models are tested against other libraries and show reasonable agreements in predicting spectral changes, as well as against MILES and MaStar libraries. The final result is a publicly available sMILES library with different abundance patterns for 801 stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
L. Mashonkina, Yu Pakhomov, T. Sitnova, A. Smogorzhevskii, P. Jablonka, V Hill
Summary: NLTE line formation is crucial for deriving elemental abundances of VMP stars, which is essential for understanding the first stars, early star formation, and chemical enrichment of galaxies. In this study, we present grids of 1D-NLTE abundance corrections and provide online tools for interpolation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
T. M. Sitnova, L. Mashonkina, A. M. Tatarnikov, O. V. Voziakova, M. A. Burlak, Yu Pakhomov, P. Jablonka, M. D. Neretina, A. Frebel
Summary: This study presents atmospheric parameters and abundances of chemical elements in metal-poor stars in three ultrafaint dwarf galaxies. The results indicate the presence of first generation stars and lower abundance ratios of Sr and Ba in the UFDs compared to other types of galaxies. Additionally, a hypothesis of Sr production in metal-poor binaries at the earliest epoch of galactic evolution is suggested.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Deepak, David L. Lambert
Summary: The study of lithium abundances in red giants from the GALAHDR3 survey has identified rare examples of Li-enriched stars with similar masses and metallicity to those in the red clump. It is suggested that Li enrichment likely occurs in all red clump stars, and that lithium synthesis is attributed to the He-core flash occurring at the tip of the red giant branch. The MESA models match the observed evolution of these stars, with a speculation that the series of He-core flashes may also lead to internal restructuring and the observed temperature spread of red clump stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
T. Ryabchikova, Yu Pakhomov, L. Mashonkina, T. Sitnova
Summary: This study presents a comparative analysis of two wide binary systems - 16 Cyg and HD 219542. The results show a small difference in chemical abundance between the A and B components in both systems, suggesting a weak influence of giant gas planets on the chemical composition of the host star's atmosphere. Additionally, the behavior of chemical elements with respect to the condensation temperature differs between 16 Cyg and HD 219542, indicating different chemical environments during their formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
T. M. Sitnova, T. Matsuno, Z. Yuan, N. F. Martin, P. Banerjee, F. Sestito, K. A. Venn, J. I. Gonzalez Hernandez
Summary: We report the discovery of a metal-poor, Li-rich giant star and measure the abundance and isotope ratio of lithium. This is the first measurement of the Li-6/Li-7 ratio in a Li-rich star, and we propose a novel method to understand the source of lithium in these stars through isotope ratio measurements.
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
Verne V. Smith, Dmitry Bizyaev, Katia Cunha, Matthew D. Shetrone, Diogo Souto, Carlos Allende Prieto, Thomas Masseron, Szabolcs Meszaros, Henrik Jonsson, Sten Hasselquist, Yeisson Osorio, D. A. Garcia-Hernandez, Bertrand Plez, Rachael L. Beaton, Jon Holtzman, Steven R. Majewski, Guy S. Stringfellow, Jennifer Sobeck
Summary: The updated H-band spectral-line list adopted by APOGEE for SDSS-IV DR16 includes both atomic and molecular lines, with adjustments made using standard stars. Compared to previous versions, DR16 features more molecular and atomic lines, as well as measurable lines from heavy elements.
ASTRONOMICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
A. M. Matas Pinto, M. Spite, E. Caffau, P. Bonifacio, L. Sbordone, T. Sivarani, M. Steffen, F. Spite, P. Francois, P. Di Matteo
Summary: Studying metal-poor stars deepens our understanding of the early stages of the universe. This study analyzed the chemical composition and orbital properties of 11 dwarf stars, finding that some of them have low lithium content but no anomalies in other elements.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Diogo Souto, Katia Cunha, Verne V. Smith
Summary: The study investigated metallicities in main-sequence stars of the young open cluster Coma Berenices using high-resolution NIR spectra, finding that metallicities are near-solar and homogeneous within the same stellar class. F-type stars showed slightly lower metallicities compared to cooler members, with atomic diffusion potentially playing a role. This dip in [Fe/H] occurred in a similar effective temperature range as seen in previous lithium and beryllium abundance analyses in the cluster.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Jasmin E. Washington, Hannah M. Lewis, Borja Anguiano, Steven R. Majewski, S. Drew Chojnowski, Verne V. Smith, Keivan G. Stassun, Carlos Allende Prieto, Katia Cunha, David L. Nidever, D. A. Garcia-Hernandez, Kaike Pan
Summary: Through the study of the LIN 358 and SMC N73 binary systems, it was found that LIN 358 is likely undergoing mass transfer, while the accretion mechanism for SMC N73 remains uncertain. Additionally, the first orbital characterization for these systems was provided, along with the first global SED fitting for SMC N73.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Robert F. Wilson, Caleb Canas, Steven R. Majewski, Katia Cunha, Verne V. Smith, Chad F. Bender, Suvrath Mahadevan, Scott W. Fleming, Johanna Teske, Luan Ghezzi, Henrik Jonsson, Rachael L. Beaton, Sten Hasselquist, Keivan Stassun, Christian Nitschelm, D. A. Garcia-Hernandez, Christian R. Hayes, Jamie Tayar
Summary: Chemical abundances of planet-hosting stars provide insight into the composition of planet-forming environments. In this study, we measured the correlation between planet occurrence and chemical abundances for ten different elements. The results show that an enhancement in element abundances corresponds to an increase in planet occurrence, but the trends are weak. We also caution against interpreting trends between planet occurrence and stellar age due to degeneracies caused by Galactic chemical evolution, and make predictions for planet occurrence rates in nearby open clusters to facilitate demographics studies of young planetary systems.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Luan Ghezzi, Cintia F. Martinez, Robert F. Wilson, Katia Cunha, Verne V. Smith, Steven R. Majewski
Summary: The study reveals differences in host-star metallicity distributions between hot and warm planetary systems, with a larger impact of multiplicity on median metallicities in multiple super-Earths compared to single super-Earths.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Diogo Souto, Katia Cunha, Verne V. Smith, C. Allende Prieto, Kevin Covey, D. A. Garcia-Hernandez, Jon A. Holtzman, Henrik Jonsson, Suvrath Mahadevan, Steven R. Majewski, Thomas Masseron, Marc Pinsonneault, Donald P. Schneider, Matthew Shetrone, Keivan G. Stassun, Ryan Terrien, Olga Zamora, Guy S. Stringfellow, Richard R. Lane, Christian Nitschelm, Barbara Rojas-Ayala
Summary: Individual chemical abundances for 14 elements are derived for a sample of M dwarfs using high-resolution, near-infrared H-band spectra. The study finds good agreement between M dwarfs in binary systems and their warmer primary stars, indicating that M dwarfs can be used to calibrate empirical relationships. However, there is a systematic offset when comparing the results with the APOGEE Stellar Parameter and Chemical Abundances Pipeline. The APOGEE spectra can be used to examine Galactic chemical evolution using large samples of selected M dwarfs.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Rafael Guerco, Solange Ramirez, Katia Cunha, Verne V. Smith, Nikos Prantzos, Kris Sellgren, Simone Daflon
Summary: Using high-resolution infrared spectra and vibration-rotation lines, the abundances of fluorine (F-19) and isotopic ratios of O-16/O-17 were derived in a sample of red giants in the Galactic center. The red giants in the Galactic center have similar fluorine and iron abundances as stars in the thin-disk population, suggesting a possible origin from core-He burning Wolf-Rayet stars, thermally pulsing AGB stars, or a combination of both. The observed increase of [F/Fe] with increasing [Fe/H] in thin-disk and Galactic center stars cannot be explained by existing chemical evolution models.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Kevin Bundy, David Law, Nick MacDonald, Kyle B. Westfall, T. Sivarani, Devika Divakar, Matthew Bershady, Meng Gu, Renbin Yan, Namrata Roy, Claire Poppett, Niv Drory
Summary: This paper evaluates the performance of optical fibers in astronomical instrumentation, especially for observing faint targets on large telescopes. By studying fiber systematics and precision sky subtraction, it demonstrates the possibility of achieving 0.1% precision sky subtraction with fiber instruments.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
C. Swastik, Ravinder K. Banyal, Mayank Narang, P. Manoj, T. Sivarani, P. Rajaguru, Athira Unni, Bihan Banerjee
Summary: This study analyzed the detailed chemical abundances of >900 exoplanet-hosting stars from different radial velocity and transit surveys. The study found a primarily negative correlation between the abundance of alpha-elements in stars and the mass of planets, and a marginally positive or zero correlation between the abundance of iron-peak elements in stars and the mass of planets. The study also found that stars hosting giant planets are relatively younger, as validated by the age of the host stars obtained from isochrone fitting. Furthermore, the later enrichment of protoplanetary material with iron and iron-peak elements is consistent with the formation of giant planets via the core accretion process. Therefore, this study indicates that the observed trends in stellar abundances and planet mass are most likely a natural consequence of Galactic chemical evolution.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Athira Unni, Mayank Narang, Thirupathi Sivarani, Manoj Puravankara, Ravinder K. Banyal, Arun Surya, S. P. Rajaguru, C. Swastik
Summary: The study explores the correlation between host star iron abundance, carbon abundance, and exoplanet occurrence rate. Carbon abundance trend follows the metallicity and shows higher values among giant-planet hosts. It is challenging to interpret the results as a consequence of Galactic Chemical Evolution or due to planet formation based on the current sample.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Avrajit Bandyopadhyay, Thirupathi Sivarani, Timothy C. Beers, A. Susmitha, Prasanta K. Nayak, Jeewan C. Pandey
Summary: This study discusses the elemental abundances, particularly lithium, in a group of newly identified, bright, very metal-poor stars. The distribution of lithium among different types of stars suggests a common origin. A scaling relation for lithium depletion with temperature is derived for red giants and main-sequence stars. The study also reveals a correlation between lithium abundance and distance from the Galactic plane, indicating mixed stellar populations.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
V. Loaiza-Tacuri, Katia Cunha, Verne V. Smith, Cintia F. Martinez, Luan Ghezzi, Simon C. Schuler, Johanna Teske, Steve B. Howell
Summary: We conducted a spectroscopic analysis of FGK-type stars observed by K2 and Kepler 1 using the Hydra spectrograph on the WIYN telescope. By deriving the effective temperatures, surface gravities, and metallicities, we were able to determine the stellar and planetary properties. Our analysis confirmed the existence of a radius gap near 1.9 times the radius of the Sun, and also validated previous findings regarding the relationship between planetary radius, orbital period, and metallicity.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
B. Barbuy, A. C. S. Friaca, H. Ernandes, T. Moura, T. Masseron, K. Cunha, V. V. Smith, D. Souto, A. Perez-Villegas, S. O. Souza, C. Chiappini, A. B. A. Queiroz, J. G. Fernandez-Trincado, P. da Silva, B. X. Santiago, F. Anders, R. P. Schiavon, M. Valentini, D. Minniti, D. Geisler, V. M. Placco, M. Zoccali, M. Schultheis, C. Nitschelm, T. C. Beers, R. Razera
Summary: This article investigates the abundance variations of sodium and aluminum in a sample of low metallicity stars and analyzes their behavior by comparing with chemodynamical models. The results show a significant spread in sodium abundance, while aluminum displays a nearly secondary-element behavior, and these stars are not identified as second-generation stars from globular clusters.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
C. Swastik, Ravinder K. Banyal, Mayank Narang, P. Manoj, T. Sivarani, Bacham E. Reddy, S. P. Rajaguru
Summary: Research findings show that directly imaged planets have host stars with metallicities close to solar, and the large scatter in metallicity suggests that a metal-rich environment may not be necessary to form massive planets at large orbital distances. Additionally, the planet mass-host star metallicity relation for directly imaged massive planets in wide orbits is very similar to that found for short-period super-Jupiters and brown dwarfs around main-sequence stars.
ASTRONOMICAL JOURNAL
(2021)