scholarly journals TYC5594-576-1: R-PROCESS ENRICHMENT METAL-POOR STAR

2021 ◽  
Vol 34 ◽  
pp. 48-52
Author(s):  
T.V. Mishenina ◽  
I.A. Usenko ◽  
A.Yu. Kniazev ◽  
V. V. Kovtyukh
Keyword(s):  
Synthetic Spectrum ◽  
Carbon Abundance ◽  
The Galaxy ◽  
The Status ◽  
Molecular Synthesis ◽  
R Process ◽  
Process Elements ◽  
Early Galaxy ◽  
First Time ◽  
Poor Population

Atmospheric parameters and elemental abundances of metal-poor Population II star  TYC5594-576-1 ([Fe/H] = –2.8) have been studied, including the elements of neutron (n-) capture processes, as an important part of the enrichment sources of early Galaxy. Na, Mg, Al, Co, Sr, Y, Zr, Mo, Ba, La, Ce, Pr, Sm, Eu, Gd, Dy, Os, and Th abundances were determined using the synthetic spectrum method, taken into account the hyperfine structure (HFS) for the Ba II, La II and Eu II lines. The abundances of Si, Ca, Sc, N were determined based on the equivalent widths of their lines. The carbon abundance was obtained by the molecular synthesis fitting for the CH region of 4300-4330 ÅÅ. For the abundances determinations of C, Na, Mg, Al, Ba, and Th the NLTE corrections have been applied.We have determined the abundances of several n- capture elements for the first time and found that the behaviour of these elements abundances shows a significant trend with increasing atomic number. The elements ratios of [Eu/Fe] = 1.85, [Ba/Eu] = –1.24, [Sr/Ba] = –1.04 confirm the status of TYC5594-576-1 as a r-process enrichment star, with lower strontium [Sr/Fe] = –0.33 and higher thorium [Th/Fe] = 1.28 abundances. The obtained europium and thorium excesses testifies to the early enrichment of the Galaxy by the r-process elements as a result of the merger of neutron stars or black holes. The carbon abundance confirms the effect of canonical additional mixing in this star.

scholarly journals R-process enrichment in ultrafaint dwarf galaxies

2020 ◽  
Vol 494 (1) ◽  
pp. 120-128 ◽  
Author(s):  
Yuta Tarumi ◽  
Naoki Yoshida ◽  
Shigeki Inoue
Keyword(s):  
Star Formation ◽  
Neutron Star ◽  
Galaxy Formation ◽  
Dwarf Galaxies ◽  
Long Distance ◽  
Stellar Feedback ◽  
The Galaxy ◽  
Star Binary ◽  
R Process ◽  
Process Elements

ABSTRACT We study the enrichment and mixing of r-process elements in ultrafaint dwarf galaxies (UFDs). We assume that r-process elements are produced by neutron-star mergers (NSMs), and examine multiple models with different natal kick velocities and explosion energies. To this end, we perform cosmological simulations of galaxy formation to follow mixing of the dispersed r-process elements driven by star formation and the associated stellar feedback in progenitors of UFDs. We show that the observed europium abundance in Reticulum II is reproduced by our inner explosion model where an NSM is triggered at the centre of the galaxy, whereas the relatively low abundance in Tucana III is reproduced if an NSM occurs near the virial radius of the progenitor galaxy. The latter case is realized only if the neutron-star binary has a large natal kick velocity and travels over a long distance of a kiloparsec before merger. In both the inner and outer explosion cases, it is necessary for the progenitor galaxy to sustain prolonged star formation over a few hundred million years after the NSM, so that the dispersed r-process elements are well mixed within the interstellar medium. Short-duration star formation results in inefficient mixing, and then a large variation is imprinted in the stellar europium abundances, which is inconsistent with the observations of Reticulum II and Tucana III.

scholarly journals The Yields of r-Process Elements and Chemical Evolution of the Galaxy

2006 ◽  
Vol 306 (1-2) ◽  
pp. 33-39 ◽  
Author(s):  
Zhe Chen ◽  
Jiang Zhang ◽  
YanPing Chen ◽  
WenYuan Cui ◽  
Bo Zhang
Keyword(s):  
Chemical Evolution ◽  
The Galaxy ◽  
R Process ◽  
Process Elements

scholarly journals Abundance Patterns Among Very Metal-Poor Stars in the Halo of the Galaxy: A Statistical Approach

2009 ◽  
Vol 5 (S262) ◽  
pp. 412-413
Author(s):  
Vinicius M. Placco ◽  
Silvia Rossi ◽  
Timothy C. Beers ◽  
Sara Lucatello
Keyword(s):  
Neutron Capture ◽  
Statistical Approach ◽  
Chemical Elements ◽  
Comprehensive Analysis ◽  
Elemental Abundances ◽  
Abundance Patterns ◽  
The Galaxy ◽  
R Process ◽  
Early Galaxy ◽  
Natural Groups

AbstractThe main goal of this work is to explore the abundance patterns of the very metal-poor stars ([Fe/H]<−2.0) observed by the HERES (Hamburg ESO R-process Enhanced Star - Christlieb et al. 2004) survey. This type of study allows the analysis of the correlations among chemical elements, and place some constraints on the operation of the neutron-capture (r and s) processes in the early Galaxy. This approach makes use of statistical tools, such as agglomerative nesting, which can identify the formation of natural groups based on relations among elemental abundances (e.g. [C/Fe], [Sr/Fe], [Ba/Fe], and [Eu/Fe]), and can also be used in a series of “large-sample like” studies.This study provides a comprehensive analysis of a sample of 326 metal-poor stars, and introduces two new subclasses (r-0 and s-I) for metal-poor stars with determined abundances of neutron-capture elements, aiming to standardize the nomenclature for those objects and, by reproducing previous results, confirms the validity of the statistical method used.

scholarly journals Using failed supernovae to constrain the Galactic r-process element production

2019 ◽  
Vol 487 (2) ◽  
pp. 1745-1753 ◽  
Author(s):  
B Wehmeyer ◽  
C Fröhlich ◽  
B Côté ◽  
M Pignatari ◽  
F-K Thielemann
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Large Fraction ◽  
Capture Process ◽  
Compact Binary ◽  
Halo Stars ◽  
The Galaxy ◽  
Binary Mergers ◽  
R Process ◽  
Process Elements

ABSTRACT Rapid neutron capture process (r-process) elements have been detected in a large fraction of metal-poor halo stars, with abundances relative to iron (Fe) that vary by over two orders of magnitude. This scatter is reduced to less than a factor of 3 in younger Galactic disc stars. The large scatter of r-process elements in the early Galaxy suggests that the r-process is made by rare events, like compact binary mergers and rare sub-classes of supernovae. Although being rare, neutron star mergers alone have difficulties to explain the observed enhancement of r-process elements in the lowest metallicity stars compared to Fe. The supernovae producing the two neutron stars already provide a substantial Fe abundance where the r-process ejecta from the merger would be injected. In this work we investigate another complementary scenario, where the r-process occurs in neutron star-black hole mergers in addition to neutron star mergers. Neutron star-black hole mergers would eject similar amounts of r-process matter as neutron star mergers, but only the neutron star progenitor would have produced Fe. Furthermore, a reduced efficiency of Fe production from single stars significantly alters the age–metallicity relation, which shifts the onset of r-process production to lower metallicities. We use the high-resolution [(20 pc)3/cell] inhomogeneous chemical evolution tool ‘ICE’ to study the outcomes of these effects. In our simulations, an adequate combination of neutron star mergers and neutron star-black hole mergers qualitatively reproduces the observed r-process abundances in the Galaxy.

scholarly journals MAGNETOROTATIONALLY DRIVEN SUPERNOVAE AS THE ORIGIN OF EARLY GALAXY r -PROCESS ELEMENTS?

2012 ◽  
Vol 750 (1) ◽  
pp. L22 ◽  
Author(s):  
C. Winteler ◽  
R. Käppeli ◽  
A. Perego ◽  
A. Arcones ◽  
N. Vasset ◽  
...  
Keyword(s):  
R Process ◽  
Process Elements ◽  
Early Galaxy

scholarly journals A luminosity distribution for kilonovae based on short gamma-ray burst afterglows

2019 ◽  
Vol 486 (1) ◽  
pp. 672-690 ◽  
Author(s):  
Stefano Ascenzi ◽  
Michael W Coughlin ◽  
Tim Dietrich ◽  
Ryan J Foley ◽  
Enrico Ramirez-Ruiz ◽  
...  
Keyword(s):  
Near Infrared ◽  
Gamma Ray ◽  
Radioactive Decay ◽  
Infrared Emission ◽  
Gamma Ray Burst ◽  
Peak Magnitude ◽  
Upper Limits ◽  
R Process ◽  
Process Elements ◽  
First Time

Abstract The combined detection of a gravitational-wave signal, kilonova, and short gamma-ray burst (sGRB) from GW170817 marked a scientific breakthrough in the field of multimessenger astronomy. But even before GW170817, there have been a number of sGRBs with possible associated kilonova detections. In this work, we re-examine these ‘historical’ sGRB afterglows with a combination of state-of-the-art afterglow and kilonova models. This allows us to include optical/near-infrared synchrotron emission produced by the sGRB as well as ultraviolet/optical/near-infrared emission powered by the radioactive decay of r-process elements (i.e. the kilonova). Fitting the light curves, we derive the velocity and the mass distribution as well as the composition of the ejected material. The posteriors on kilonova parameters obtained from the fit were turned into distributions for the peak magnitude of the kilonova emission in different bands and the time at which this peak occurs. From the sGRB with an associated kilonova, we found that the peak magnitude in H bands falls in the range [−16.2, −13.1] ($95{{\ \rm per\ cent}}$ of confidence) and occurs within $0.8\!-\!3.6\, \rm d$ after the sGRB prompt emission. In g band instead we obtain a peak magnitude in range [−16.8, −12.3] occurring within the first 18 h after the sGRB prompt. From the luminosity distributions of GW170817/AT2017gfo, kilonova candidates GRB130603B, GRB050709, and GRB060614 (with the possible inclusion of GRB150101B, GRB050724A, GRB061201, GRB080905A, GRB150424A, and GRB160821B) and the upper limits from all the other sGRBs not associated with any kilonova detection we obtain for the first time a kilonova luminosity distribution in different bands.

scholarly journals Silver Stars

2009 ◽  
Vol 5 (S265) ◽  
pp. 67-68
Author(s):  
Camilla Juul Hansen ◽  
Francesca Primas
Keyword(s):  
Neutron Capture ◽  
Heavy Elements ◽  
Capture Process ◽  
Elemental Abundances ◽  
The Galaxy ◽  
Formation And Evolution ◽  
R Process ◽  
Process Elements ◽  
Heaviest Elements ◽  
Process Element

AbstractThe rapid neutron-capture process (r-process), which produces some of the heaviest elements, is not well understood. Obtaining accurate abundances of these heavy elements (Z > 38) is important, both in the context of the chemical evolution of the Galaxy and for understanding the site(s) and process(es) of formation of those elements. We have determined elemental abundances for several r-process elements, notably silver, from high resolution VLT/UVES spectra. Silver was chosen because it is predominantly a light r-process element (38 < Z < 50), and little is known about its formation and evolution in the Galaxy. Here, we present our preliminary results.

Distribution of R- and S-Process Elements in the Galactic Halo

1988 ◽  
Vol 132 ◽  
pp. 501-506
Author(s):  
C. Sneden ◽  
C. A. Pilachowski ◽  
K. K. Gilroy ◽  
J. J. Cowan
Keyword(s):  
Heavy Element ◽  
Galactic Halo ◽  
Low Noise ◽  
Heavy Elements ◽  
Process Synthesis ◽  
Element Abundances ◽  
Halo Stars ◽  
Abundance Patterns ◽  
R Process ◽  
Process Elements

Current observational results for the abundances of the very heavy elements (Z&gt;30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

Victorian Pain

2017 ◽  
Author(s):  
Rachel Ablow
Keyword(s):  
Nineteenth Century ◽  
Victorian Literature ◽  
Social Life ◽  
Charles Darwin ◽  
Harriet Martineau ◽  
The Status ◽  
History Of ◽  
The Individual ◽  
Natural Philosophers ◽  
First Time

The nineteenth century introduced developments in science and medicine that made the eradication of pain conceivable for the first time. This new understanding of pain brought with it a complex set of moral and philosophical dilemmas. If pain serves no obvious purpose, how do we reconcile its existence with a well-ordered universe? Examining how writers of the day engaged with such questions, this book offers a compelling new literary and philosophical history of modern pain. The book provides close readings of novelists Charlotte Brontë and Thomas Hardy and political and natural philosophers John Stuart Mill, Harriet Martineau, and Charles Darwin, as well as a variety of medical, scientific, and popular writers of the Victorian age. The book explores how discussions of pain served as investigations into the status of persons and the nature and parameters of social life. No longer conceivable as divine trial or punishment, pain in the nineteenth century came to seem instead like a historical accident suggesting little or nothing about the individual who suffers. A landmark study of Victorian literature and the history of pain, the book shows how these writers came to see pain as a social as well as a personal problem. Rather than simply self-evident to the sufferer and unknowable to anyone else, pain was also understood to be produced between persons—and even, perhaps, by the fictions they read.

The Legal Status of Local Government in South Africa under the New Constitutional Dispensation

2018 ◽  
Vol 33 (2) ◽  
Author(s):  
Mbuzeni Mathenjwa
Keyword(s):  
South Africa ◽  
Local Government ◽  
Legal Status ◽  
Case Law ◽  
The Status ◽  
History Of ◽  
The Republic ◽  
First Time

The history of local government in South Africa dates back to a time during the formation of the Union of South Africa in 1910. With regard to the status of local government, the Union of South Africa Act placed local government under the jurisdiction of the provinces. The status of local government was not changed by the formation of the Republic of South Africa in 1961 because local government was placed under the further jurisdiction of the provinces. Local government was enshrined in the Constitution of the Republic of South Africa arguably for the first time in 1993. Under the interim Constitution local government was rendered autonomous and empowered to regulate its affairs. Local government was further enshrined in the final Constitution of 1996, which commenced on 4 February 1997. The Constitution refers to local government together with the national and provincial governments as spheres of government which are distinctive, interdependent and interrelated. This article discusses the autonomy of local government under the 1996 Constitution. This it does by analysing case law on the evolution of the status of local government. The discussion on the powers and functions of local government explains the scheme by which government powers are allocated, where the 1996 Constitution distributes powers to the different spheres of government. Finally, a conclusion is drawn on the legal status of local government within the new constitutional dispensation.

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