THE EFFECT OF THE14N(p, γ)15O REACTION ON THE BLUE LOOPS IN INTERMEDIATE-MASS STARS

Halabi, Ghina M.; Eid, M. F. El; Champagne, Arthur E

doi:10.1088/0004-637x/761/1/10

Cited by 18 publications

(22 citation statements)

References 30 publications

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“…The minimum core masses at the first thermal pulse and first TDU are higher in the Z = 0.007 models. Besides the difference in metallicity, the stellar evolutionary code used for the calculations has been updated to use the LUNA rate (Bemmerer et al 2006) of which govern energy generation during core He burning and therefore the size of the core at the beginning of the AGB (e.g., Castellani et al 1992;Imbriani et al 2001;Halabi et al 2012).…”

Section: The Third Dredge-upmentioning

confidence: 99%

Helium enrichment and carbon-star production in metal-rich populations

Karakas

2014

Monthly Notices of the Royal Astronomical Society

101

141

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We present new theoretical stellar evolutionary models of metal-rich asymptotic giant branch (AGB) stars. Stellar models are evolved with initial masses between 1M ⊙ and 7M ⊙ at Z = 0.007, and 1M ⊙ and 8M ⊙ at Z = 0.014 (solar) and at Z = 0.03. We evolve models with a canonical helium abundance and with helium enriched compositions (Y = 0.30, 0.35, 0.40) at Z = 0.014 and Z = 0.03. The efficiency of third dredge-up and the mass range of carbon stars decreases with an increase in metallicity. We predict carbon stars form from initial masses between 1.75-7M ⊙ at Z = 0.007 and between 2-4.5M ⊙ at solar metallicity. At Z = 0.03 the mass range for C-star production is narrowed to 3.25-4M ⊙ . The third dredge-up is reduced when the helium content of the model increases owing to the reduced number of thermal pulses on the AGB. A small increase of ∆Y = 0.05 is enough to prevent the formation of C stars at Z = 0.03, depending on the mass-loss rate, whereas at Z = 0.014, an increase of ∆Y 0.1 is required to prevent the formation of C stars. We speculate that the probability of finding C stars in a stellar population depends as much on the helium abundance as on the metallicity. To explain the paucity of C stars in the inner region of M31 we conclude that the observed stars have Y 0.35 or that the stellar metallicity is higher than [Fe/H] ≈ 0.1.

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Section: The Third Dredge-upmentioning

confidence: 99%

Helium enrichment and carbon-star production in metal-rich populations

Karakas

2014

Monthly Notices of the Royal Astronomical Society

101

141

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“…The mean reason behind triggering the blue loop is the enforcement of the SHB. A recent study showing the sensitivity of the loop formation to convective mixing and nuclear reaction is presented by [1]. It is intersecting to note that these blue loops occur in the region of the cepheid instabilities so that available observations may be used for testing the theoretical description of their formation (see [1] for details).…”

Section: The Evolution To the Agb Phasementioning

confidence: 99%

“…A recent study showing the sensitivity of the loop formation to convective mixing and nuclear reaction is presented by [1]. It is intersecting to note that these blue loops occur in the region of the cepheid instabilities so that available observations may be used for testing the theoretical description of their formation (see [1] for details). The core helium burning phase ends after the position 6, and the star evolves back to the RGB, where envelope convection develops again and this is the second dredge up episode which is marked in the right panel in Fig.…”

Section: The Evolution To the Agb Phasementioning

confidence: 99%

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Nucleosynthesis in asymptotic giant branch stars

Eid

2014

AIP Conference Proceedings

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The nucleosynthesis in asymptotic giant branch stars (briefly: AGB)is a challenging and fascinating subject in the theory of stellar evolution and important for observations as well. This is because about of half the heavy elements beyond iron are synthesized during thermal pulsation phases of these stars. Furthermore, the understanding of the production of the heavy elements and some light elements like carbon and fluorine represent a powerful tool to get more insight into the internal structure of these stars. The diversity of nuclear processing during the AGB phases may also motivate experimental activities in measuring important nuclear reactions. In this contribution, we emphasize several interesting feature of the nucleosynthesis in AGB stars which still needs further elaboration especially from theoretical point of view.

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“…We use the mixing scheme described in [13]. The overshooting distance is expressed as l= H p , where H p is the pressure scale height.…”

Section: Effect Of Core Overshootingmentioning

confidence: 99%

Effect of 12C+12C reaction & convective mixing on the progenitor mass of ONe white dwarfs

Halabi¹,

Eid²

2015

AIP Conference Proceedings

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Abstract. Stars in the mass range ~8 -12 M are the most numerous massive stars. This mass range is critical because it may lead to supernova (SN) explosion, so it is important for the production of heavy elements and the chemical evolution of the galaxy. We investigate the critical transition mass (M up ), which is the minimum initial stellar mass that attains the conditions for hydrostatic carbon burning. Stars of masses < M up evolve to the Asymptotic Giant Branch and then develop CO White Dwarfs, while stars of masses M up ignite carbon in a partially degenerate CO core and form electron degenerate ONe cores. These stars evolve to the Super AGB (SAGB) phase and either become progenitors of ONe White Dwarfs or eventually explode as electron-capture SN (EC-SN). We study the sensitivity of M up to the C-burning reaction rate and to the treatment of convective mixing. In particular, we show the effect of a recent determination of the ¹²C+¹²C fusion rate, as well as the extension of the convective core during hydrogen and helium burning on M up in solar metallicity stars. We choose the 9 M characteristics of the evolution with the new C-burning rate.

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THE EFFECT OF THE¹⁴N(p, γ)¹⁵O REACTION ON THE BLUE LOOPS IN INTERMEDIATE-MASS STARS

Cited by 18 publications

References 30 publications

Helium enrichment and carbon-star production in metal-rich populations

Helium enrichment and carbon-star production in metal-rich populations

Nucleosynthesis in asymptotic giant branch stars

Effect of 12C+12C reaction & convective mixing on the progenitor mass of ONe white dwarfs

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