Oxygen Abundances in Unevolved Metal‐poor Stars from Near‐Ultraviolet OH Lines

Israelian, G.; López, R. J. García; Реболо, Р.

doi:10.1086/306351

Cited by 221 publications

(344 citation statements)

References 49 publications

(97 reference statements)

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“…On the other hand, both the CRS and LECR models predict a linear evolution, consistent with the observations, although Fields & Olive (1998) recently suggested that the CRI model should still be considered as viable, based on their re-analysis of the data including O in low metallicity stars (Israelian, Garcia Lopez, & Rebolo 1998).…”

Section: Introduction and Overviewsupporting

confidence: 64%

“…For both the CRS and LECR cases, the accelerated particle composition is independent of [Fe/H] and the same as that of the current epoch cosmic rays, except that there are no protons and α-particles for the latter. The ambient medium composition is solar scaled with Fe/H, except that for the CRI case we also consider a slower decrease of the O abundance, O/H=(O/H) 10 0.6 [Fe/H] , which fits the recent Israelian et al (1998) data. Such a modification of the ambient medium abundances has only a negligible effect on the calculations for the CRS and LECR models.…”

Section: The Energetics Of Be Productionmentioning

confidence: 75%

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Li Be B Energetics and Cosmic Ray Origin

Ramaty

Lingenfelter

1999

Galaxy Evolution: Connecting the Distant Universe With the Local Fossil Record

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Abstract.Three different models have been proposed for LiBeB production by cosmic rays: the CRI model in which the cosmic rays are accelerated out of an ISM of solar composition scaled with metallicity; the CRS model in which cosmic rays with composition similar to that of the current epoch cosmic rays are accelerated out of fresh supernova ejecta; and the LECR model in which a distinct low energy component coexists with the postulated cosmic rays of the CRI model. These models are usually distinguished by their predictions concerning the evolution of the Be and B abundances. Here we emphasize the energetics which favor the CRS model. This model is also favored by observations showing that the bulk (80 to 90%) of all supernovae occur in hot, low density superbubbles, where supernova shocks can accelerate the cosmic rays from supernova ejecta enriched matter.

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Section: Introduction and Overviewsupporting

confidence: 64%

Section: The Energetics Of Be Productionmentioning

confidence: 75%

Li Be B Energetics and Cosmic Ray Origin

Ramaty

Lingenfelter

1999

Galaxy Evolution: Connecting the Distant Universe With the Local Fossil Record

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“…In order to convert from [O/H] to the iron metallicities [Fe/H], we have used the extensive sample of disk stars by Edvardsson et al (1993), from which we derive the relationship The dashed line is the predicted relationship on the basis of the radial gradients of young objects in the galactic disk, at galactocentric distances 4 ≤ R(kpc) ≤ 12, as discussed by Maciel (2002). The figure also includes some representative observational data by Barbuy & Erdelyi-Mendes (1989), asterisks; Boesgaard et al (1999), filled squares; Edvardsson et al (1993), crosses;Israelian et al (1998), solid dots; Spiesman & Wallerstein (1991), open circles; Spite & Spite (1991), plus signs; Takeda et al (2002), empty squares; Mishenina et al (2000), open stars, and Cavallo et al (1997), filled stars, as recomputed by Mishenina et al (2000).…”

Section: The [O/h] × [Fe/h] Relationmentioning

confidence: 76%

An estimate of the time variation of the O/H radial gradient from planetary nebulae

Maciel¹,

Costa²,

Uchida³

2002

A&A

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Abstract. Radial abundance gradients are a common feature of spiral galaxies, and in the case of the Galaxy both the magnitude of the gradients and their variations are among the most important constraints of chemical evolution models. Planetary nebulae (PN) are particularly interesting objects to study the gradients and their variations. Owing to their bright emission spectra, they can be observed even at large galactocentric distances, and the derived abundances are relatively accurate, with uncertainties of about 0.1 to 0.2 dex, particularly for the elements that are not synthesized in their progenitor stars. On the other hand, as the offspring of intermediate mass stars, with main sequence masses in the interval of 1 to 8 solar masses, they are representative of objects with a reasonable age span. In this paper, we present an estimate of the time variation of the O/H radial gradient in a sample containing over 200 nebulae with accurate abundances. Our results are consistent with a flattening of the O/H gradient roughly from −0.11 dex/kpc to −0.06 dex/kpc during the last 9 Gyr, or from −0.08 dex/kpc to −0.06 dex/kpc during the last 5 Gyr.

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“…Attention was sharply focussed on oxygen abundances in metal-poor stars by studies of the OH ultraviolet lines (Israelian et al 1998(Israelian et al , 2001Boesgaard et al 1999). These showed that [O/Fe] …”

Section: [O I] and The Oxygen Problemmentioning

confidence: 99%

“…A comparison is illuminating given the heat the "oxygen problem" has generated in recent times. Eight of our programme stars were analysed by Israelian et al (1998) or Israelian et al (2001). Differences in adopted model atmosphere parameters are small: ∆T eff = 91 ± 103 K, ∆ log g = 0.18 ± 0.26, and ∆ [Fe/H] (Table 4) and those from OH is −0.06 dex.…”

Section: [O I] and Oh Linesmentioning

confidence: 99%