FROM THE COLOR-MAGNITUDE DIAGRAM OF Ω CENTAURI AND (SUPER-)ASYMPTOTIC GIANT BRANCH STELLAR MODELS TO a GALACTIC PLANE PASSAGE GAS PURGING CHEMICAL EVOLUTION SCENARIO

Herwig, Falk; VandenBerg, Don A.; Navarro, Julio F.; Ferguson, Jason W.; Paxton, Bill

doi:10.1088/0004-637x/757/2/132

Cited by 30 publications

(33 citation statements)

References 110 publications

(187 reference statements)

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“…In super-AGB star modelling, the amount (and even occurrence) of TDU is hotly debated, with computations finding no TDU (e.g. Siess 2010; Ventura et al 2013), low efficiency TDU with λ ~ 0.07–0.3 (Ritossa et al 1996), moderate efficiency TDU with λ ~ 0.4–0.8 (Doherty et al 2015) and high efficiency TDU with λ > 1 (Herwig et al 2012; Jones et al 2016a). Although quantitative differences exist between evolutionary calculations from different research groups, the general trend is for decreasing TDU efficiency (or cessation of TDU entirely) as one transitions from intermediate/massive AGB stars, meaning those with initial masses ≳ 5 M ⊙ but not massive enough to ignite carbon, to super-AGB stars, which do ignite carbon.…”

Section: Evolutionmentioning

confidence: 99%

Super-AGB Stars and their Role as Electron Capture Supernova Progenitors

Doherty

Gil‐Pons

Siess

et al. 2017

Publ. Astron. Soc. Aust.

164

193

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We review the lives, deaths and nucleosynthetic signatures of intermediate-mass stars in the range ≈6-12 M , which form super-AGB stars near the end of their lives. The critical mass boundaries both between different types of massive white dwarfs (CO, CO-Ne, ONe), and between white dwarfs and supernovae, are examined along with the relative fraction of super-AGB stars that end life either as an ONe white dwarf or as a neutron star (or an ONeFe white dwarf), after undergoing an electron capture supernova event. The contribution of the other potential single-star channel to electroncapture supernovae, that of the failed massive stars, is also discussed. The factors that influence these different final fates and mass limits, such as composition, rotation, the efficiency of convection, the nuclear reaction rates, mass-loss rates, and third dredge-up efficiency, are described. We stress the importance of the binary evolution channels for producing electron-capture supernovae. Recent nucleosynthesis calculations and elemental yield results are discussed and a new set of s-process heavy element yields is presented. The contribution of super-AGB star nucleosynthesis is assessed within a Galactic perspective, and the (super-)AGB scenario is considered in the context of the multiple stellar populations seen in globular clusters. A brief summary of recent works on dust production is included. Last, we conclude with a discussion of the observational constraints and potential future advances for study into these stars on the low mass/high mass star boundary.

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Section: Evolutionmentioning

confidence: 99%

Super-AGB Stars and their Role as Electron Capture Supernova Progenitors

Doherty

Gil‐Pons

Siess

et al. 2017

Publ. Astron. Soc. Aust.

164

193

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“…, in-between which the core increases very slowly in mass, at a rate of approximately 10 −7 −10 −6 M yr −1 . The rate of core growth depends crucially, however, on the efficiency, λ, of the third dredge-up (Herwig et al 2012;Ventura et al 2013;Jones et al 2016b;Doherty et al 2017). The thermal pulses themselves are the result of thermal instabilities in the He-burning shell, which is of the order of a mere 10 −4 −10 −5 M of material (see, e.g.…”

mentioning

confidence: 99%

Remnants and ejecta of thermonuclear electron-capture supernovae

Jones

Roepke

Fryer

et al. 2019

A&A

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The explosion mechanism of electron-capture supernovae (ECSNe) remains equivocal: it is not completely clear whether these events are implosions in which neutron stars are formed, or incomplete thermonuclear explosions that leave behind bound ONeFe white dwarf remnants. Furthermore, the frequency of occurrence of ECSNe is not known, though it has been estimated to be of the order of a few per cent of all core-collapse supernovae. We attempt to constrain the explosion mechanism (neutron-star-forming implosion or thermonuclear explosion) and the frequency of occurrence of ECSNe using nucleosynthesis simulations of the latter scenario, population synthesis, the solar abundance distribution, pre-solar meteoritic oxide grain isotopic ratio measurements and the white dwarf mass–radius relation. Tracer particles from the 3d hydrodynamic simulations were post-processed with a large nuclear reaction network in order to determine the complete compositional state of the bound ONeFe remnant and the ejecta, and population synthesis simulations were performed in order to estimate the ECSN rate with respect to the CCSN rate. The 3d deflagration simulations drastically overproduce the neutron-rich isotopes 48Ca, 50Ti, 54Cr , 60Fe and several of the Zn isotopes relative to their solar abundances. Using the solar abundance distribution as our constraint, we place an upper limit on the frequency of thermonuclear ECSNe as 1−3% the frequency at which core-collapse supernovae (FeCCSNe) occur. This is on par with or 1 dex lower than the estimates for ECSNe from single stars. The upper limit from the yields is also in relatively good agreement with the predictions from our population synthesis simulations. The 54Cr/52Cr and 50Ti/48Ti isotopic ratios in the ejecta are a near-perfect match with recent measurements of extreme pre-solar meteoritc oxide grains, and 53Cr/52Cr can also be matched if the ejecta condenses before mixing with the interstellar medium. The composition of the ejecta of our simulations implies that ECSNe, including accretion-induced collapse of oxygen-neon white dwarfs, could actually be partial thermonuclear explosions and not implosions that form neutron stars. There is still much work to do to improve the hydrodynamic simulations of such phenomena, but it is encouraging that our results are consistent with the predictions from stellar evolution modelling and population synthesis simulations, and can explain several key isotopic ratios in a sub-set of pre-solar oxide meteoritic grains. Theoretical mass–radius relations for the bound ONeFe WD remnants of these explosions are apparently consistent with several observational WD candidates. The composition of the remnants in our simulations can reproduce several, but not all, of the spectroscopically-determined elemental abundances from one such candidate WD.

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“…The survival and migration of such massive star clusters is also key to the build-up of NSCs in dwarf galaxies, some of which may survive as the dense cores of their host galaxy during accretion to the MW (e.g. ωCen; Herwig et al 2012).…”

Section: The Pegasus Dirr Galaxy and Its Star Clustermentioning

confidence: 99%

Globular cluster ejection, infall, and the host dark matter halo of the Pegasus dwarf galaxy

Leaman

Ruiz-Lara

Cole

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Recent photometric observations revealed a massive, extended (MGC ≳ 105 M⊙; Rh ∼ 14 pc) globular cluster (GC) in the central region (D3D ≲ 100 pc) of the low-mass (M* ∼ 5 × 106 M⊙) dwarf irregular galaxy Pegasus. This massive GC offers a unique opportunity to study star cluster inspiral as a mechanism for building up nuclear star clusters, and the dark matter (DM) density profile of the host galaxy. Here, we present spectroscopic observations indicating that the GC has a systemic velocity of ΔV = 3 ± 8 km s−1 relative to the host galaxy, and an old, metal-poor stellar population. We run a suite of orbital evolution models for a variety of host potentials (cored to cusped) and find that the GC’s observed tidal radius (which is ∼3 times larger than the local Jacobi radius), relaxation time, and relative velocity are consistent with it surviving inspiral from a distance of Dgal ≳ 700 pc (up to the maximum tested value of Dgal = 2000 pc). In successful trials, the GC arrives to the galaxy centre only within the last ∼1.4 ± 1 Gyr. Orbits that arrive in the centre and survive are possible in DM haloes of nearly all shapes, however to satisfy the GC’s structural constraints a galaxy DM halo with mass MDM ≃ 6 ± 2 × 109 M⊙, concentration c ≃ 13.7 ± 0.6, and an inner slope to the DM density profile of −0.9 ≤ γ ≤ −0.5 is preferred. The gas densities necessary for its creation and survival suggest the GC could have formed initially near the dwarf’s centre, but then was quickly relocated to the outskirts where the weaker tidal field permitted an increased size and relaxation time – with the latter preserving the former during subsequent orbital decay.

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FROM THE COLOR-MAGNITUDE DIAGRAM OF Ω CENTAURI AND (SUPER-)ASYMPTOTIC GIANT BRANCH STELLAR MODELS TO a GALACTIC PLANE PASSAGE GAS PURGING CHEMICAL EVOLUTION SCENARIO

Cited by 30 publications

References 110 publications

Super-AGB Stars and their Role as Electron Capture Supernova Progenitors

Super-AGB Stars and their Role as Electron Capture Supernova Progenitors

Remnants and ejecta of thermonuclear electron-capture supernovae

Globular cluster ejection, infall, and the host dark matter halo of the Pegasus dwarf galaxy

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