Europium isotope ratios in s-process element-enhanced metal-poor stars: A new probe of the 151Sm branching

Wako Aoki; Sean G. Ryan; Nobuyuki Iwamoto; Timothy C. Beers; John E. Norris; Hiroyasu Ando; Toshitaka Kajino; Grant J. Mathews; Masayuki Y. Fujimoto

doi:10.1086/377681

Europium isotope ratios in s-process element-enhanced metal-poor stars: A new probe of the ¹⁵¹Sm branching

Wako Aoki^*, Sean G. Ryan, Nobuyuki Iwamoto, Timothy C. Beers, John E. Norris, Hiroyasu Ando, Toshitaka Kajino, Grant J. Mathews, Masayuki Y. Fujimoto

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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Abstract

We report on the first measurement of the Eu isotope fractions ( ¹⁵¹Eu and ¹⁵³Eu) in s-process element-enhanced metal-poor stars. We use these ratios to investigate the ¹⁵¹Sm branching of s-process nucleosynthesis. The measurement was made by detailed study of Eu II lines that are significantly affected by hyperfine splitting and isotope shifts in spectra of the carbon-rich very metal poor stars LP 625-44 and CS 31062-050, observed with the Subaru Telescope High Dispersion Spectrograph. The ¹⁵¹Eu fractions [fr(¹⁵¹Eu) = ¹⁵¹Eu/( ¹⁵¹Eu + ¹⁵¹Eu)] derived for LP 625-44 and CS 31062-050 are 0.60 and 0.55, respectively, with uncertainties of about ±0.05. These values are higher than found in solar system material but agree well with the predictions of recent sprocess models. We derive new constraints on the temperature and neutron density during the s-process based on calculations of pulsed s-process models for the ¹⁵¹Eu fraction.

Original language	English
Pages (from-to)	L67-L70
Journal	Astrophysical Journal
Volume	592
Issue number	2 II
DOIs	https://doi.org/10.1086/377681
Publication status	Published - 1 Aug 2003

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@article{7a670930d50a4e26996dc6f388b94fc4,

title = "Europium isotope ratios in s-process element-enhanced metal-poor stars: A new probe of the 151Sm branching",

abstract = "We report on the first measurement of the Eu isotope fractions ( 151Eu and 153Eu) in s-process element-enhanced metal-poor stars. We use these ratios to investigate the 151Sm branching of s-process nucleosynthesis. The measurement was made by detailed study of Eu II lines that are significantly affected by hyperfine splitting and isotope shifts in spectra of the carbon-rich very metal poor stars LP 625-44 and CS 31062-050, observed with the Subaru Telescope High Dispersion Spectrograph. The 151Eu fractions [fr(151Eu) = 151Eu/( 151Eu + 151Eu)] derived for LP 625-44 and CS 31062-050 are 0.60 and 0.55, respectively, with uncertainties of about ±0.05. These values are higher than found in solar system material but agree well with the predictions of recent sprocess models. We derive new constraints on the temperature and neutron density during the s-process based on calculations of pulsed s-process models for the 151Eu fraction.",

keywords = "Nuclear reactions, nucleosynthesis, abundances, Stars: AGE and post-AGB, Stars: Population II, Stars: abundances",

author = "Wako Aoki and Ryan, {Sean G.} and Nobuyuki Iwamoto and Beers, {Timothy C.} and Norris, {John E.} and Hiroyasu Ando and Toshitaka Kajino and Mathews, {Grant J.} and Fujimoto, {Masayuki Y.}",

year = "2003",

month = aug,

day = "1",

doi = "10.1086/377681",

language = "English",

volume = "592",

pages = "L67--L70",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "2 II",

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TY - JOUR

T1 - Europium isotope ratios in s-process element-enhanced metal-poor stars

T2 - A new probe of the 151Sm branching

AU - Aoki, Wako

AU - Ryan, Sean G.

AU - Iwamoto, Nobuyuki

AU - Beers, Timothy C.

AU - Norris, John E.

AU - Ando, Hiroyasu

AU - Kajino, Toshitaka

AU - Mathews, Grant J.

AU - Fujimoto, Masayuki Y.

PY - 2003/8/1

Y1 - 2003/8/1

N2 - We report on the first measurement of the Eu isotope fractions ( 151Eu and 153Eu) in s-process element-enhanced metal-poor stars. We use these ratios to investigate the 151Sm branching of s-process nucleosynthesis. The measurement was made by detailed study of Eu II lines that are significantly affected by hyperfine splitting and isotope shifts in spectra of the carbon-rich very metal poor stars LP 625-44 and CS 31062-050, observed with the Subaru Telescope High Dispersion Spectrograph. The 151Eu fractions [fr(151Eu) = 151Eu/( 151Eu + 151Eu)] derived for LP 625-44 and CS 31062-050 are 0.60 and 0.55, respectively, with uncertainties of about ±0.05. These values are higher than found in solar system material but agree well with the predictions of recent sprocess models. We derive new constraints on the temperature and neutron density during the s-process based on calculations of pulsed s-process models for the 151Eu fraction.

AB - We report on the first measurement of the Eu isotope fractions ( 151Eu and 153Eu) in s-process element-enhanced metal-poor stars. We use these ratios to investigate the 151Sm branching of s-process nucleosynthesis. The measurement was made by detailed study of Eu II lines that are significantly affected by hyperfine splitting and isotope shifts in spectra of the carbon-rich very metal poor stars LP 625-44 and CS 31062-050, observed with the Subaru Telescope High Dispersion Spectrograph. The 151Eu fractions [fr(151Eu) = 151Eu/( 151Eu + 151Eu)] derived for LP 625-44 and CS 31062-050 are 0.60 and 0.55, respectively, with uncertainties of about ±0.05. These values are higher than found in solar system material but agree well with the predictions of recent sprocess models. We derive new constraints on the temperature and neutron density during the s-process based on calculations of pulsed s-process models for the 151Eu fraction.

KW - Nuclear reactions, nucleosynthesis, abundances

KW - Stars: AGE and post-AGB

KW - Stars: Population II

KW - Stars: abundances

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U2 - 10.1086/377681

DO - 10.1086/377681

M3 - Article

SN - 0004-637X

VL - 592

SP - L67-L70

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2 II

ER -

Europium isotope ratios in s-process element-enhanced metal-poor stars: A new probe of the ¹⁵¹Sm branching

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