Schweißen von Temperguß

Maeder, Hans

doi:10.1007/978-3-663-05569-3

Cited by 3 publications

(3 citation statements)

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“…Carigi (2000) computed chemical evolution models for the Galactic disk, under an inside-out formation scenario, based on different combinations of seven sets of stellar yields by different authors; the ∆Y /∆O spread predicted by her models is in the 2.9 to 4.6 range for the Galactocentric distance of M17 (5.9 kpc). Carigi et al (1995), based on yields by Maeder (1992), computed closed box models adequate for irregular galaxies, like the SMC, and obtained ∆Y /∆O = 2.95. They also computed models with galactic outflows of well mixed material, that yielded ∆Y /∆O values similar to those of the closed box models, and models with galactic outflows of O-rich material that yielded values higher than 2.95.…”

Section: The Primordial Helium Abundancementioning

confidence: 99%

The Chemical Composition of the Small Magellanic Cloud HiiRegion NGC 346 and the Primordial Helium Abundance

Peimbert

Ruíz

2000

ApJ

181

243

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Spectrophotometry in the λλ 3400-7400 range is presented for 13 areas of the brightest H ii region in the SMC: NGC 346. The observations were obtained at CTIO with the 4-m telescope. Based on these observations its chemical composition is derived. The helium and oxygen abundances by mass are given by: Y (SMC)= 0.2405 ± 0.0018 and O(SMC)= 0.00171 ± 0.00025. From models and observations of irregular and blue compact galaxies it is found that ∆Y /∆O = 3.5 ± 0.9 and consequently that the primordial helium abundance by mass is given by: Y p = 0.2345 ± 0.0026(1σ). This result is compared with values derived from Big Bang nucleosynthesis, and with other determinations of Y p .

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Section: The Primordial Helium Abundancementioning

confidence: 99%

The Chemical Composition of the Small Magellanic Cloud HiiRegion NGC 346 and the Primordial Helium Abundance

Peimbert

Ruíz

2000

ApJ

181

243

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“…It is generally inferred from core collapse simulations that single stars more massive than ∼ 20 − 25 M ⊙ form black holes (e.g., Fryer 1999). Stars more massive than ∼ 20 − 25 M ⊙ in binaries are also expected to form black holes in order to explain the Galactic black hole transient systems and to satisfy nucleosynthetic constraints (e.g., Maeder 1992;Portegies Zwart, Verbunt & Ergma 1997;Kobulnicky & Skillman 1997;Ergma & van den Heuvel 1998). However, a number of studies have been pointed out that binary interactions can significantly increase the neutron star/black hole mass formation limit.…”

Section: Introductionmentioning

confidence: 99%

The Most Massive Progenitors of Neutron Stars: CXO J164710.2−455216

Belczyński

Taam

2008

Astrophysical Journal

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The evolution leading to the formation of a neutron star in the very young Westerlund 1 star cluster is investigated. The turnoff mass has been estimated to be ∼ 35 M ⊙ , indicating a cluster age ∼ 3 − 5 Myr. The brightest X-ray source in the cluster, CXO J164710.2-455216, is a slowly spinning (10 s) single neutron star and potentially a magnetar. Since this source was argued to be a member of the cluster, the neutron star progenitor must have been very massive (M zams ∼ > 40 M ⊙ ) as noted by Muno et al. (2006). Since such massive stars are generally believed to form black holes (rather than neutron stars), the existence of this object poses a challenge for understanding massive star evolution. We point out while single star progenitors below M zams ∼ < 20 M ⊙ form neutron stars, binary evolution completely changes the progenitor mass range. In particular, we demonstrate that mass loss in Roche lobe overflow enables stars as massive as 50 − 80 M ⊙ , under favorable conditions, to form neutron stars. If the very high observed binary fraction of massive stars in Westerlund 1 ( ∼ > 70%) is considered, it is natural that CXO J164710.2-455216 was formed in a binary which was disrupted in a supernova explosion such that it is now found as a single neutron star. Hence, the existence of a neutron star in a given stellar population does not necessarily place stringent constraints on progenitor mass when binary interactions are considered. It is concluded that the existence of a neutron star in Westerlund 1 cluster is fully consistent with the generally accepted framework of stellar evolution.

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“…In England and Wales, in 1955, 31 per cent of all infant deaths occurred in the first day of life (Ministry of Health, 1957). In the United States of America "nearly 40,000 infants fail to survive the first 24 hours of life" (Maeder, 1957). The majority ,of these deaths are associated with asphyxia and few would disagree with Smith and Cook (1955) who state that "ventilatory difficulty accounts for approximately 50 per cent of neonatal mortality".…”

Section: Introductionmentioning

confidence: 99%

Maternal and Obstetric Factors in Asphyxia Neonatorum With a Preliminary Report on a Possible Association With Abo Blood Groups

Amiel

1960

BJOG

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Schweißen von Temperguß

Cited by 3 publications

References 0 publications

The Chemical Composition of the Small Magellanic Cloud HiiRegion NGC 346 and the Primordial Helium Abundance

The Chemical Composition of the Small Magellanic Cloud HiiRegion NGC 346 and the Primordial Helium Abundance

The Most Massive Progenitors of Neutron Stars: CXO J164710.2−455216

Maternal and Obstetric Factors in Asphyxia Neonatorum With a Preliminary Report on a Possible Association With Abo Blood Groups

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