Enrichment of S-process elements in the progenitor of SN 1987A

1988 ◽  
pp. 274-280
Author(s):  
R. E. Williams
Keyword(s):  
Sn 1987A ◽  
Process Elements

scholarly journals Enrichment of s-Process Elements in the Progenitor of SN 1987A

1988 ◽  
Vol 108 ◽  
pp. 274-280
Author(s):  
R.E. Williams
Keyword(s):  
Massive Stars ◽  
Absorption Lines ◽  
Scattering Model ◽  
Sn 1987A ◽  
Model Yield ◽  
Process Elements

AbstractExisting calculations of s-process nucleosynthesis in massive stars such as Sk −69° 202 show enhancements in the He-burning shells which, when mixed to the surface, lead to Sc, Sr, and Ba enrichments of factors of 2 to 15. Abundances derived from the supernova absorption lines using a simple scattering model yield enhancements of this magnitude. Thus, the observed and predicted s-process abundances are roughly in accord, although the Ba/Sr ratio derived for the supernova may be higher than the s-process can account for.

SN 1987A Revisited as a Major Production Site for [CLC][ITAL]r[/ITAL][/CLC]-Process Elements

2001 ◽  
Vol 561 (1) ◽  
pp. L97-L100 ◽  
Author(s):  
Takuji Tsujimoto ◽  
Toshikazu Shigeyama
Keyword(s):  
Sn 1987A ◽  
Production Site ◽  
Process Elements

Spectral Analysis of SN 1987A: the First 7 Months

1988 ◽  
Vol 7 (4) ◽  
pp. 434-442 ◽  
Author(s):  
P. Höflich
Keyword(s):  
Radiation Transport ◽  
Stellar Structure ◽  
Strong Mixing ◽  
Addition Line ◽  
Chemical Abundances ◽  
Mixing Processes ◽  
Model Calculations ◽  
Sn 1987A ◽  
Metal Abundances ◽  
Process Elements

AbstractModel calculations for the photospheres of SN 1987A are presented. Spherical symmetry and density profiles are assumed to be given by the homologous expansion of the stellar structure of a B3I supergiant. For later stages the density slopes are determined. For a number of elements (H, He, C, N, O, Ne, Na, Mg, K, Ca, Ba) detailed atomic models are used. The statistical equations and the radiation transport are treated consistently as well for the lines as for the continua. In addition, line blanketing due to other elements are included under the assumption of pure scattering. The importance of a sophisticated NLTE-treatment is demonstrated. Chemical metal abundances are derived by comparing the observed and synthetic spectra. Good agreement is found if a third of solar abundance for all elements with the exception of the s-process elements is assumed. An overabundance of He by a factor of 1-2 is indicated by the models corresponding to the time before June 87. No gradient in the chemical abundances of the hydrogen rich layers has to be assumed. Up to October 87 the He abundance at the photosphere is increased to 5 times solar, i.e. the continua are formed in helium rich layers. The chemical profile indicates strong mixing processes of the different layers of the progenitor during the explosion. Additionally, pecularities of hydrogen line profiles are discussed. Mainly, they can be understood by selective line blanketing effects. The total mass of the hydrogen rich shell is estimated to amount to be 9-11 M⊙.

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>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.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

Nuclear γ ray lines in the supernova SN 1987a

1991 ◽  
Vol 16 (4) ◽  
pp. 443-457
Author(s):  
R. Lehoucq ◽  
Ph. Durouchouxa
Keyword(s):  
Sn 1987A ◽  
Γ Ray

The origin of r-process elements

Science ◽  
2021 ◽  
Vol 371 (6532) ◽  
pp. 901.18-903
Author(s):  
Keith T. Smith
Keyword(s):  
R Process ◽  
Process Elements

Evaluation of the Fetal Therapy Evidence in Lower Urinary Tract Obstruction: Would an ERAS Guideline Improve Outcomes?

2021 ◽  
pp. 1-13
Author(s):  
R. Douglas Wilson ◽  
Gregg Nelson
Keyword(s):  
Quality Improvement ◽  
Urinary Tract ◽  
Lower Urinary Tract ◽  
Urinary Tract Obstruction ◽  
Fetal Surgery ◽  
Fetal Therapy ◽  
Lower Urinary Tract Obstruction ◽  
Evidenced Based ◽  
Process Elements ◽  
Lower Urinary

<b><i>Background:</i></b> Pregnancies that are prenatally identified to have fetal anomalies are complex and require expert multidisciplinary care. As many conditions can impact the fetus prenatally and require intervention, an enhanced recovery after surgery (ERAS) for lower urinary tract obstruction (LUTO) is being evaluated to determine the level of evidenced-based data available. <b><i>Problem:</i></b> The percutaneous ultrasound-guided fetal surgery procedure for bladder neck obstruction is the focus for elements of preoperative counseling, intraoperative procedure/risk complications, and postoperative management. <b><i>Methods:</i></b> A quality improvement review Squire 2.0 (2000–2020) was undertaken for the percutaneous LUTO fetal surgery shunting (lower urinary tract obstruction), process and procedure which require 2 process pathways, one to evaluate the fetal candidate and a second to treat. This structured review is focused on identifying the process elements to allow the determination of the number of evidenced-based elements that would allow for audit and measurement of the clinical element variance for comparative feedback to the individual surgical provider or surgery center. <b><i>Interventions:</i></b> Titles and abstracts were screened to identify potentially relevant articles with priority given to meta-analyses, systematic reviews, randomized controlled studies, nonrandomized controlled studies, reviews, and case series. <b><i>Results:</i></b> A series of potential clinical elements for the diagnostic fetal evaluation and for the 3 protocol areas of surgical care for the procedures (pre-, intra-, and postoperative care) are identified using an ERAS-like process. <b><i>Conclusions:</i></b> The identified clinical elements have the potential for ERAS-LUTO fetal therapy guideline. Multidisciplinary collaboration (surgeon, anesthesia, nursing, imaging, and laboratory) is required for ERAS quality improvement in the pre-, intra-, and postoperative processes. Process elements in each of the operative areas can be audited, evaluated, compared, and modified/improved.

scholarly journals The AMBRE Project: r-process elements in the Milky Way thin and thick discs

2018 ◽  
Vol 619 ◽  
pp. A143 ◽  
Author(s):  
G. Guiglion ◽  
P. de Laverny ◽  
A. Recio-Blanco ◽  
N. Prantzos
Keyword(s):  
Chemical Evolution ◽  
Milky Way ◽  
Element Abundances ◽  
Thick Disc ◽  
Thin Disc ◽  
Solar Metallicity ◽  
R Process ◽  
Process Elements ◽  
Process Element ◽  
The Eu

Context. The chemical evolution of neutron capture elements in the Milky Way disc is still a matter of debate. There is a lack of statistically significant catalogues of such element abundances, especially those of the r-process. Aims. We aim to understand the chemical evolution of r-process elements in Milky Way disc. We focus on three pure r-process elements Eu, Gd, and Dy. We also consider a pure s-process element, Ba, in order to disentangle the different nucleosynthesis processes. Methods. We take advantage of high-resolution FEROS, HARPS, and UVES spectra from the ESO archive in order to perform a homogeneous analysis on 6500 FGK Milky Way stars. The chemical analysis is performed thanks to the automatic optimization pipeline GAUGUIN. We present abundances of Ba (5057 stars), Eu (6268 stars), Gd (5431 stars), and Dy (5479 stars). Based on the [α/Fe] ratio determined previously by the AMBRE Project, we chemically characterize the thin and the thick discs, and a metal-rich α-rich population. Results. First, we find that the [Eu/Fe] ratio follows a continuous sequence from the thin disc to the thick disc as a function of the metallicity. Second, in thick disc stars, the [Eu/Ba] ratio is found to be constant, while the [Gd/Ba] and [Dy/Ba] ratios decrease as a function of the metallicity. These observations clearly indicate a different nucleosynthesis history in the thick disc between Eu and Gd–Dy. The [r/Fe] ratio in the thin disc is roughly around +0.1 dex at solar metallicity, which is not the case for Ba. We also find that the α-rich metal-rich stars are also enriched in r-process elements (like thick disc stars), but their [Ba/Fe] is very different from thick disc stars. Finally, we find that the [r/α] ratio tends to decrease with metallicity, indicating that supernovae of different properties probably contribute differently to the synthesis of r-process elements and α-elements. Conclusions. We provide average abundance trends for [Ba/Fe] and [Eu/Fe] with rather small dispersions, and for the first time for [Gd/Fe] and [Dy/Fe]. This data may help to constrain chemical evolution models of Milky Way r- and s-process elements and the yields of massive stars. We emphasize that including yields of neutron-star or black hole mergers is now crucial if we want to quantitatively compare observations to Galactic chemical evolution models.

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