Spectroscopic Analysis of 33 of the Most Metal Poor Stars. II.

McWilliam, Andrew; Preston, George W.; Sneden, Christopher; Searle, Leonard

doi:10.1086/117486

Cited by 749 publications

(1,038 citation statements)

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“…This includes the "iron" peak, which was usually assumed to be co-produced with the r-nuclei. This result was implied by the early observations by McWilliam et al [142] and [143]. Much more extensive work on low-metallicity halo stars (cf.…”

Section: Estimates Of the Ism Inventory Of Short-lived Nucleimentioning

confidence: 75%

Short-lived nuclei in the early Solar System: Possible AGB sources

et al. 2006

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The abundances of short-lived radionuclides in the early solar system (ESS) are reviewed, as well as the methodology used in determining them. These results are compared with the inventory estimated for a uniform galactic production model. It is shown that, to within a factor of two, the observed abundances of 238 U, 235 U, 232 Th, 244 Pu, 182 Hf, 146 Sm, and 53 Mn are roughly compatible with long-term galactic nucleosynthesis. 129 I is an exception, with an ESS inventory much lower than expected from uniform production. The isotopes 107 Pd, 60 Fe, 41 Ca, 36 Cl, 26 Al, and 10 Be require late addition to the protosolar nebula. 10 Be is the product of energetic particle irradiation of the solar system as most probably is 36 Cl. Both of these nuclei appear to be present when 26 Al is absent. A late injection by a supernova (SN) cannot be responsible for most of the short-lived nuclei without excessively producing 53 Mn; it can however be the source of 53 Mn itself and possibly of 60 Fe. If a late SN injection is responsible for these two nuclei, then there remains the problem of the origin of 107 Pd and several other isotopes. Emphasis is given to an AGB star as a source of many of the nuclei, including 60 Fe; this possibility is explored with a new generation of stellar models. It is shown that if the dilution factor (i.e. the ratio of the contaminating mass to the solar parental cloud mass) is f 0 ∼ 4×10 −3 , a reasonable representation for many nuclei is obtained; this requires that ( 60 Fe/ 56 Fe) ESS ∼ 10 −7 to 2×10 −6 . The nuclei produced by an AGB source do not include 53 Mn, 10 Be or 36 Cl if it is very abundant. The role of irradiation is discussed with regard to 26 Al, 36 Cl and 41 Ca, and the estimates of bulk solar abundances of these isotopes are commented on. The conflict between various scenarios is emphasized as well as the current absence of an astrophysically plausible global interpretation for all the existing data. Examination of abundances for the actinides indicates that a quiescent interval of ∼ 10 8 years is required for actinide group production. This is needed in order to explain the data on 244 Pu and the new bounds on 247 Cm. Because this quiescent interval is not compatible with the 182 Hf data, a separate type of r-process event is needed for at least the actinides, distinct from the two types that have previously been identified. The apparent coincidence of the 129 I and trans-actinide time scales suggests that the last heavy r contribution was from an r-process that produced very heavy nuclei but without fission recycling so that the yields at Ba and below (including I) were governed by fission.

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Section: Estimates Of the Ism Inventory Of Short-lived Nucleimentioning

confidence: 75%

Short-lived nuclei in the early Solar System: Possible AGB sources

et al. 2006

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“…Zhao and Magain's (1990b) EW data were analyzed with (T eff , log g, and ξ) values taken from Magain (1989) and [Fe/H] values taken from Zhao and Magain(1990a). McWilliam et al's (1995a) EW data were analyzed with the parameters taken from McWilliam et al (1995b).…”

Section: Literature Data Analysismentioning

confidence: 99%

“…to ∼ −4) by the extensive study of McWilliam et al (1995b) using the resonance D lines (Na i 5890/5896). It should be pointed out that most of these previous studies were done based on the assumption of LTE.…”

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confidence: 99%

Non-LTE Analysis of the Sodium Abundance of Metal-Poor Stars in the Galactic Disk and Halo

Takeda

Zhao

Takada-Hidai

et al. 2003

Chin. J. Astron. Astrophys.

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“…The precise nature of this early r-process unfortunately remains elusive. (Burris et al 2000;Jehin et al 1999;Edvardsson et al 1993;McWilliam et al 1995, McWilliam 1998. r-process rich stars from Westin et al (2000); Sneden et al (2003), Hill et al 2002 andCowan et al (2002).…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Cosmic Evolution of r-Process Elements

Truran

Otsuki

2005

Proc. IAU

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Abstract. The rapid neutron capture process (r-process) is understood to be responsible for the synthesis of approximately half of all of the isotopes present in Solar System matter in the mass region from approximately zinc through the actinides. While the general features of this process were identified in the classic papers by B 2 FH (1957) and Cameron (1957), our current understanding of the r-process remains woefully incomplete. We have yet to cleanly identify which of the studied astrophysical sites contribute significantly to the observed abundance pattern. We have yet to reconcile the apparent duplicity of r-process sites with extant models for the operation of the r-process in diverse astronomical environments. While we may still remain theoretically challenged in our attempts to understand the r-process mechanism and to identify its site, significant clues have come from the observational side. Triggered by the first detections of the element europium (formed predominantly by the r-process) in low metallicity stars (Spite & Spite 1978), observations of heavy element abundances in halo stars have since served to provide tremendously important clues to the nature of the r-process mechanism. Identified constraints include: the utter dominance of the r-process contributions (over those of the s-process in extremely metal deficient stars; an extraordinary robustness of the r-process pattern in the mass range A > ∼ 130-140; and the demand for a second r-process site for the production of the A < ∼ 130 r-process nuclei. We will review these observational trends and theoretical models in the context of the Galactic (Cosmic) evolution of r-process abundances.

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Spectroscopic Analysis of 33 of the Most Metal Poor Stars. II.

Cited by 749 publications

References 0 publications

Short-lived nuclei in the early Solar System: Possible AGB sources

Short-lived nuclei in the early Solar System: Possible AGB sources

Non-LTE Analysis of the Sodium Abundance of Metal-Poor Stars in the Galactic Disk and Halo

Cosmic Evolution of r-Process Elements

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