ORCID Profile
0000-0003-2952-859X
Current Organisations
Medical University of Warsaw
,
Monash University
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In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Astronomical and Space Sciences | Astronomy And Astrophysics | Stellar Astronomy and Planetary Systems | Galactic Astronomy | Numerical Analysis | Astronomical and Space Instrumentation | Optics And Opto-Electronic Physics | Instruments And Techniques | Atomic And Molecular Physics | Theoretical Physics | Pattern Recognition and Data Mining | Fluid Physics | Cosmology and Extragalactic Astronomy | Nuclear Physics
Physical sciences | Expanding Knowledge in the Physical Sciences | Scientific instrumentation | Expanding Knowledge in the Information and Computing Sciences | Mathematical sciences | Computer software and services not elsewhere classified | Expanding Knowledge in Technology |
Publisher: EDP Sciences
Date: 11-09-2008
Publisher: AIP
Date: 2008
DOI: 10.1063/1.2916973
Publisher: American Astronomical Society
Date: 10-06-1998
DOI: 10.1086/305730
Publisher: American Astronomical Society
Date: 10-10-2006
DOI: 10.1086/506957
Publisher: Oxford University Press (OUP)
Date: 27-04-2014
DOI: 10.1093/MNRAS/STU571
Publisher: Oxford University Press (OUP)
Date: 06-1988
Publisher: American Astronomical Society
Date: 03-2006
DOI: 10.1086/499263
Publisher: American Astronomical Society
Date: 12-1986
DOI: 10.1086/164810
Publisher: American Astronomical Society
Date: 02-1987
DOI: 10.1086/184823
Publisher: AIP
Date: 2007
DOI: 10.1063/1.2818983
Publisher: IOP Publishing
Date: 07-2016
Publisher: American Astronomical Society
Date: 12-2006
DOI: 10.1086/508504
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-12-2006
Abstract: Low-mass stars, ∼1 to 2 solar masses, near the Main Sequence are efficient at producing the helium isotope 3 He, which they mix into the convective envelope on the giant branch and should distribute into the Galaxy by way of envelope loss. This process is so efficient that it is difficult to reconcile the low observed cosmic abundance of 3 He with the predictions of both stellar and Big Bang nucleosynthesis. Here we find, by modeling a red giant with a fully three-dimensional hydrodynamic code and a full nucleosynthetic network, that mixing arises in the supposedly stable and radiative zone between the hydrogen-burning shell and the base of the convective envelope. This mixing is due to Rayleigh-Taylor instability within a zone just above the hydrogen-burning shell, where a nuclear reaction lowers the mean molecular weight slightly. Thus, we are able to remove the threat that 3 He production in low-mass stars poses to the Big Bang nucleosynthesis of 3 He.
Publisher: American Astronomical Society
Date: 10-02-2016
Publisher: EDP Sciences
Date: 16-10-2006
Publisher: Cambridge University Press (CUP)
Date: 2003
DOI: 10.1071/AS03010
Abstract: We investigate the production of aluminium and magnesium in asymptotic giant branch models covering a wide range in mass and composition. We evolve models from the pre-main sequence, through all intermediate stages, to near the end of the thermally-pulsing asymptotic giant branch phase. We then perform detailed nucleosynthesis calculations from which we determine the production of the magnesium and aluminium isotopes as a function of the stellar mass and composition. We present the stellar yields of sodium and the magnesium and aluminium isotopes. We discuss the abundance predictions from the stellar models in reference to abundance anomalies observed in globular cluster stars.
Publisher: American Astronomical Society
Date: 20-09-2006
DOI: 10.1086/505593
Publisher: Cambridge University Press (CUP)
Date: 22-07-2014
DOI: 10.1017/PASA.2014.21
Abstract: The chemical evolution of the Universe is governed by the chemical yields from stars, which in turn are determined primarily by the initial stellar mass. Even stars as low as 0.9 M ⊙ can, at low metallicity, contribute to the chemical evolution of elements. Stars less massive than about 10 M ⊙ experience recurrent mixing events that can significantly change the surface composition of the envelope, with observed enrichments in carbon, nitrogen, fluorine, and heavy elements synthesized by the slow neutron capture process (the s -process). Low- and intermediate-mass stars release their nucleosynthesis products through stellar outflows or winds, in contrast to massive stars that explode as core-collapse supernovae. Here we review the stellar evolution and nucleosynthesis for single stars up to ~ 10 M ⊙ from the main sequence through to the tip of the asymptotic giant branch (AGB). We include a discussion of the main uncertainties that affect theoretical calculations and review the latest observational data, which are used to constrain uncertain details of the stellar models. We finish with a review of the stellar yields available for stars less massive than about 10 M ⊙ and discuss efforts by various groups to address these issues and provide homogeneous yields for low- and intermediate-mass stars covering a broad range of metallicities.
Publisher: American Astronomical Society
Date: 11-1989
DOI: 10.1086/167999
Publisher: Cambridge University Press (CUP)
Date: 2009
DOI: 10.1071/AS09008
Abstract: We present montage , a post-processing nucleosynthesis code that combines a traditional network for isotopes lighter than calcium with a rapid algorithm for calculating the s -process nucleosynthesis of the heavier isotopes. The separation of those parts of the network where only neutron-capture and beta-decay reactions are significant provides a substantial advantage in computational efficiency. We present the yields for a complete set of s -process isotopes for a 3-M ⊙ , Z = 0.02 stellar model, as a demonstration of the utility of the approach. Future work will include a large grid of models suitable for use in calculations of Galactic chemical evolution.
Publisher: Cambridge University Press (CUP)
Date: 08-2018
DOI: 10.1017/S1743921318007019
Abstract: I present a subjective list of what I think are the most serious problems in the modelling of AGB stars. Because AGB stars represent the last phase of stellar evolution, they suffer from the accumulation of the effects of uncertainties in all the earlier phases. The complexity of AGB evolution adds further uncertainties specific to the evolutionary behaviour of those stars. Most of the problems are associated with mixing, specifically the boundaries of mixed regions. The nature of the “extra-mixing” remains a mystery, let alone how to model it reliably. Other problems are briefly mentioned and I finish with some hopes of making progress in the future.
Publisher: American Astronomical Society
Date: 06-1993
DOI: 10.1086/172705
Publisher: American Astronomical Society
Date: 05-2002
DOI: 10.1086/339733
Publisher: Oxford University Press (OUP)
Date: 06-06-2007
Publisher: Cambridge University Press (CUP)
Date: 11-2009
DOI: 10.1017/S1743921310004539
Abstract: We examine the effects of thermohaline mixing on the composition of the envelopes of low-metallicity asymptotic giant branch (AGB) stars. We have evolved models of 1, 1.5 and 2M ⊙ and of metallicity Z = 10 −4 from the pre-main sequence to the end of the thermal pulsing asymptotic giant branch with thermohaline mixing applied throughout the simulations. We find that the small amount of 3 He that remains after the first giant branch is enough to drive thermohaline mixing on the AGB and that the mixing is most efficient in the early thermal pulses, with the efficiency dropping from pulse to pulse. We note a surprising increase in the 7 Li abundance, with log 10 ϵ( 7 Li) reaching values of over 2.5 in the 1.5M ⊙ model. It is thus possible to get stars which are both C- and Li-rich at the same time. We compare our models to measurements of carbon and lithium in carbon-enhanced metal-poor stars which have not yet reached the giant branch. These models can simultaneously reproduced the observed C and Li abundances of carbon-enhanced metal-poor turn-off stars that are Li-rich.
Publisher: American Physical Society (APS)
Date: 13-02-2006
Publisher: American Astronomical Society
Date: 09-1989
DOI: 10.1086/185522
Publisher: Oxford University Press (OUP)
Date: 11-2013
Publisher: American Astronomical Society
Date: 23-03-2009
Publisher: Elsevier BV
Date: 05-2001
Publisher: Oxford University Press (OUP)
Date: 07-1985
Publisher: Oxford University Press (OUP)
Date: 17-06-2017
Publisher: American Astronomical Society
Date: 04-03-2014
Publisher: American Astronomical Society
Date: 06-08-2015
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921307010927
Abstract: With the first discovery of surviving pre-solar minerals in primitive meteorites in 1987 a new kind of astronomy emerged, based on the study of stellar condensates with all the detailed methods available to modern analytical laboratories. The pre-solar origin of the grains is indicated by considerable isotopic ratio variations compared with Solar System materials, characteristic of nuclear processes in different types of stars.
Publisher: Oxford University Press (OUP)
Date: 15-05-2017
Publisher: AIP
Date: 1995
DOI: 10.1063/1.47367
Publisher: EDP Sciences
Date: 15-05-2008
Publisher: Cambridge University Press (CUP)
Date: 08-2015
DOI: 10.1017/S1743921316000909
Abstract: Commission 35 (C35), “Stellar Constitution”, consists of members of the International Astronomical Union whose research spans many aspects of theoretical and observational stellar physics and it is mainly focused on the comprehension of the properties of stars, stellar populations and galaxies. The number of members of C35 increased progressively over the last ten years and currently C35 comprises about 400 members. C35 was part of Division IV (Stars) until 2014 and then became part of Division G (Stars and Stellar Physics), after the main IAU reorganisation in 2015. Four Working Groups have been created over the years under Division IV, initially, and Division G later: WG on Active B Stars, WG on Massive Stars, WG on Abundances in Red Giant and WG on Chemically Peculiar and Related Stars. In the last decade the Commission had 4 presidents, Wojciech Dziembowski (2003-2006), Francesca D'Antona (2006-2009), Corinne Charbonnel (2009-2012) and Marco Limongi (2012-2015), who were assisted by an Organizing Committee (OC), usually composed of about 10 members, all of them elected by the C35 members and holding their positions for three years. The C35 webpage ( iau-c35.stsci.edu ) has been designed and continuously maintained by Claus Leitherer from the Space Telescope Institute, who deserves our special thanks. In addition to the various general information on the Commission structure and activities, it contains links to various resources, of interest for the members, such as stellar models, evolutionary tracks and isochrones, synthetic stellar populations, stellar yields and input physics (equation of state, nuclear cross sections, opacity tables), provided by various groups. The main activity of the C35 OC is that of evaluating, ranking and eventually supporting the proposals for IAU sponsored meetings. In the last decade the Commission has supported several meetings focused on topics more or less relevant to C35. Since the primary aim of this document is to present the main activity of C35 over the last ten years, in the following we present some scientific highlights that emerged from the most relevant IAU Symposia and meetings supported and organized by C35 in the last decade.
Publisher: American Astronomical Society
Date: 13-03-2015
Publisher: AIP
Date: 2008
DOI: 10.1063/1.2916959
Publisher: Cambridge University Press (CUP)
Date: 1983
DOI: 10.1017/S1323358000016970
Abstract: Star formation is believed to occur in interstellar clouds consisting of both gas and grains. Under the gravitational influence of such a cloud the constituent dust grains sediment toward the centre, and both calculations and implications of this sedimentation have been published by many authors (McCrea and Williams 1965 Horedt 1973, 1976 Prentice 1976 Krautschneider 1977 Flannery and Krook 1978 and others). Two main results from these calculations warrant our attention. Firstly, the timescale for appreciable sedimentation T s ≃ 10 7 -10 8 years, which is consistent with age estimates of many clouds (Harrison 1978, Blitz and Shu 1980). Secondly, the sedimentation proceeds more rapidly for larger grains. This leads to an increase of mean grain size toward the centre of the cloud.
Publisher: Oxford University Press (OUP)
Date: 06-05-2015
DOI: 10.1093/MNRAS/STV770
Publisher: Oxford University Press (OUP)
Date: 03-1984
Publisher: American Astronomical Society
Date: 24-07-2014
Publisher: Springer Berlin Heidelberg
Date: 1989
DOI: 10.1007/BFB0114919
Publisher: Oxford University Press (OUP)
Date: 09-09-2017
Publisher: Oxford University Press (OUP)
Date: 08-2000
Publisher: Elsevier BV
Date: 07-2002
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-08-2014
Abstract: We can learn about the solar system's past by measuring heavy radioactive isotopes in meteorites—the extraterrestrial equivalent of carbon dating on Earth. Elements heavier than iron are mainly synthesized in supernovae or asymptotic giant branch (AGB) stars. Knowing exactly which element is produced where, is key to dating the solar system. Lugaro et al. found that AGB stars generated more of a nuclide called 182 Hf than previously thought (see the Perspective by Bizzarro). Its abundance indicates that it was produced about 30 million years before the Sun's formation. Science , this issue p. 650 see also p. 620
Publisher: Elsevier BV
Date: 07-2005
Publisher: Oxford University Press (OUP)
Date: 29-07-2015
Publisher: American Astronomical Society
Date: 24-01-2011
Publisher: American Astronomical Society
Date: 04-2003
DOI: 10.1086/367887
Publisher: Springer Netherlands
Date: 1987
Publisher: Cambridge University Press (CUP)
Date: 08-2007
DOI: 10.1017/S1743921307000567
Abstract: Low-mass stars, ∼ 1–2 solar masses, near the Main Sequence are efficient at producing 3 He, which they mix into the convective envelope on the giant branch and distribute into the Galaxy by way of envelope loss. This process is so efficient that it is difficult to reconcile the observed cosmic abundance of 3 He with the predictions of Big Bang nucleosynthesis. In this paper we find, by modeling a red giant with a fully three-dimensional hydrodynamic code and a full nucleosynthetic network, that mixing arises in the supposedly stable and radiative zone between the hydrogen-burning shell and the base of the convective envelope. This mixing is due to Rayleigh-Taylor instability within a zone just above the hydrogen-burning shell. In this zone the burning of the 3 He left behind by the retreating convective envelope is predominantly by the reaction 3 He + 3 He → 4 He + 1 H + 1 H, a reaction which, untypically for stellar nuclear reactions, lowers the mean molecular weight, leading to a local minimum. This local minimum leads to Rayleigh-Taylor instability, and turbulent motion is generated which will continue ultimately up into the normal convective envelope. Consequently material from the envelope is dragged down sufficiently close to the burning shell that the He in it is progressively destroyed. Thus we are able to remove the threat that He production in low-mass stars poses to the Big Bang nucleosynthesis of 3 He. Some slow mixing mechanism has long been suspected, that connects the convective envelope of a red giant to the burning shell. It appears to be necessary to account for progressive changes in the C/C and N/C ratios on the First Giant Branch. We suggest that these phenomena are also due to the Rayleigh-Taylor-unstable character of the He-burning region.
Publisher: Cambridge University Press (CUP)
Date: 08-2015
DOI: 10.1017/S1743921316005767
Abstract: Super Asymptotic Giant Branch (Super-AGB) stars reside in the mass range ≈ 6.5-10 M ⊙ and bridge the ide between low/intermediate-mass and massive stars. They are characterised by off-centre carbon ignition prior to a thermally pulsing phase which can consist of many tens to even thousands of thermal pulses. With their high luminosities and very large, cool, red stellar envelopes, these stars appear seemingly identical to their slightly more massive red supergiant counterparts. Due to their similarities, super-AGB stars may therefore act as stellar imposters and contaminate red supergiant surveys. The final fate of super-AGB stars is also quite uncertain and depends primarily on the competition between the core growth and mass-loss rates. If the stellar envelope is removed prior to the core reaching ≈ 1.375 M ⊙ , an O-Ne white dwarf will remain, otherwise the star will undergo an electron-capture supernova (EC-SN) leaving behind a neutron star. We determine the relative fraction of super-AGB stars that end life as either an O-Ne white dwarf or as a neutron star, and provide a mass limit for the lowest mass supernova over a broad range of metallicities from the Z=0.02 to 0.0001.
Publisher: AIP
Date: 2007
DOI: 10.1063/1.2818997
Publisher: American Astronomical Society
Date: 10-2001
DOI: 10.1086/322415
Publisher: Springer Science and Business Media LLC
Date: 2002
Publisher: AIP
Date: 2012
DOI: 10.1063/1.4754386
Publisher: Wiley
Date: 12-1990
Publisher: EDP Sciences
Date: 09-2017
Publisher: Oxford University Press (OUP)
Date: 20-04-2016
Publisher: Oxford University Press (OUP)
Date: 05-2007
Publisher: American Astronomical Society
Date: 08-2019
Publisher: AIP
Date: 2012
DOI: 10.1063/1.4754389
Publisher: Cambridge University Press (CUP)
Date: 2003
DOI: 10.1071/AS03059
Abstract: Asymptotic giant branch stars are expected to produce 22 Ne through the combined H and He burning that operates during their thermally pulsing evolution. However, observationally there is a fairly tight correlation between the O and Ne abundances as measured in planetary nebulae in various populations. In this paper we use recent detailed stellar evolutionary calculations for compositions appropriate to the Galaxy and the Large Magellanic Cloud, in an attempt to determine if the models are consistent with the observed abundances. We show that there is only a narrow range in stellar mass, about 2 to 4 M ⊙ (lower for lower [Fe/H]) where 22 Ne is produced in sufficient quantities to affect the total observed elemental neon abundance, which is mostly 20 Ne. The models appear to be consistent with the observations, but a more thorough analysis is required.
Publisher: Oxford University Press (OUP)
Date: 21-05-2013
DOI: 10.1093/MNRAS/STT728
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.EJVS.2013.07.020
Abstract: ACST-2 is currently the largest trial ever conducted to compare carotid artery stenting (CAS) with carotid endarterectomy (CEA) in patients with severe asymptomatic carotid stenosis requiring revascularization. Patients are entered into ACST-2 when revascularization is felt to be clearly indicated, when CEA and CAS are both possible, but where there is substantial uncertainty as to which is most appropriate. Trial surgeons and interventionalists are expected to use their usual techniques and CE-approved devices. We report baseline characteristics and blinded combined interim results for 30-day mortality and major morbidity for 986 patients in the ongoing trial up to September 2012. A total of 986 patients (687 men, 299 women), mean age 68.7 years (SD ± 8.1) were randomized equally to CEA or CAS. Most (96%) had ipsilateral stenosis of 70-99% (median 80%) with contralateral stenoses of 50-99% in 30% and contralateral occlusion in 8%. Patients were on appropriate medical treatment. For 691 patients undergoing intervention with at least 1-month follow-up and Rankin scoring at 6 months for any stroke, the overall serious cardiovascular event rate of periprocedural (within 30 days) disabling stroke, fatal myocardial infarction, and death at 30 days was 1.0%. Early ACST-2 results suggest contemporary carotid intervention for asymptomatic stenosis has a low risk of serious morbidity and mortality, on par with other recent trials. The trial continues to recruit, to monitor periprocedural events and all types of stroke, aiming to randomize up to 5,000 patients to determine any differential outcomes between interventions. ISRCTN21144362.
Publisher: Cambridge University Press (CUP)
Date: 08-2015
DOI: 10.1017/S1743921316004725
Abstract: The Monχey project will provide a large and homogeneous set of stellar yields for the low- and intermediate- mass stars and has applications particularly to galactic chemical evolution modelling. We describe our detailed grid of stellar evolutionary models and corresponding nucleosynthetic yields for stars of initial mass 0.8 M ⊙ up to the limit for core collapse supernova (CC-SN) ≈ 10 M ⊙ . Our study covers a broad range of metallicities, ranging from the first, primordial stars (Z = 0) to those of super-solar metallicity (Z = 0.04). The models are evolved from the zero-age main-sequence until the end of the asymptotic giant branch (AGB) and the nucleosynthesis calculations include all elements from H to Bi. A major innovation of our work is the first complete grid of heavy element nucleosynthetic predictions for primordial AGB stars as well as the inclusion of extra-mixing processes (in this case thermohaline) during the red giant branch. We provide a broad overview of our results with implications for galactic chemical evolution as well as highlight interesting results such as heavy element production in dredge-out events of super-AGB stars. We briefly introduce our forthcoming web-based database which provides the evolutionary tracks, structural properties, internal/surface nucleosynthetic compositions and stellar yields. Our web interface includes user- driven plotting capabilities with output available in a range of formats. Our nucleosynthetic results will be available for further use in post processing calculations for dust production yields.
Publisher: Oxford University Press (OUP)
Date: 11-07-2009
Publisher: Oxford University Press (OUP)
Date: 24-08-2018
Publisher: American Astronomical Society
Date: 07-1991
DOI: 10.1086/170179
Publisher: American Astronomical Society
Date: 11-2005
DOI: 10.1086/444615
Publisher: Cambridge University Press (CUP)
Date: 2007
DOI: 10.1071/AS07021
Abstract: We present stellar yields calculated from detailed models of low and intermediate-mass asymptotic giant branch (AGB) stars. We evolve models with a range of mass from 1 to 6 M ⊙ , and initial metallicities from solar to 1/200th of the solar metallicity. Each model was evolved from the zero age main sequence to near the end of the thermally pulsing (TP) AGB phase, and through all intermediate phases including the core He-flash for stars initially less massive than 2.5 M ⊙ . For each mass and metallicity, we provide tables containing structural details of the stellar models during the TP-AGB phase, and tables of the stellar yields for 74 species from hydrogen through to sulfur, and for a small number of iron-group nuclei. All tables are available for download. Our results have many applications including use in population synthesis studies and the chemical evolution of galaxies and stellar systems, and for comparison to the composition of AGB and post-AGB stars and planetary nebulae.
Publisher: Cambridge University Press (CUP)
Date: 2009
DOI: 10.1071/AS09048
Publisher: American Astronomical Society
Date: 05-1991
DOI: 10.1086/191569
Publisher: Cambridge University Press (CUP)
Date: 04-2008
DOI: 10.1017/S1743921308022850
Abstract: We have calculated a set of low-mass (0.85 M ⊙ ≤ M ≤ 3.0 M ⊙ ) zero metallicity and extremely metal-poor (−6.5 ≤ [Fe/H] ≤ −3.0) stellar models, including nucleosynthetic yields for 74 species. As far as we are aware these are the first detailed yields in the mass and metallicity range considered. Due to the difficulty in modelling such stars the yields naturally contain numerous uncertainties, and thus present interesting challenges for future stellar modelling. We briefly present some results in the context of the Galactic Halo star observations, and also discuss qualitatively some of the uncertainties in the modelling. We conclude by suggesting that much work is still necessary in this research area. For ex le, multidimensional fluid dynamics models are needed to simulate the violent proton ingestion events that occur during the core He flash and early TPAGB, observations and theory of mass loss at low metallicities are needed, the effects of reaction rate uncertainties need to be quantified, and low temperature opacities variable in carbon (and nitrogen) need to be included in the models.
Publisher: EDP Sciences
Date: 2006
DOI: 10.1051/EAS:2006032
Publisher: Cambridge University Press (CUP)
Date: 2017
DOI: 10.1017/PASA.2017.52
Abstract: 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 electron-capture 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.
Publisher: American Astronomical Society
Date: 06-02-2017
Publisher: Cambridge University Press (CUP)
Date: 2003
DOI: 10.1071/ASV20N4_IN
Publisher: Oxford University Press (OUP)
Date: 07-2015
Publisher: Cambridge University Press (CUP)
Date: 2002
DOI: 10.1071/AS02013
Abstract: We present new evolutionary sequences for low and intermediate mass stars (1−6 M ⊙ ) for three different metallicities, Z = 0.02, 0.008, and 0.004. We evolve the models from the pre-main sequence to the thermally-pulsing asymptotic giant branch phase. We have two sequences of models for each mass, one which includes mass loss and one without mass loss. Typically 20 or more pulses have been followed for each model, allowing us to calculate the third dredge-up parameter for each case. Using the results from this large and homogeneous set of models, we present an approximate fit for the core mass at the first thermal pulse, M c 1 , as well as for the third dredge-up efficiency parameter, λ, and the core mass at the first dredge-up episode, M c min , as a function of metallicity and total mass. We also examine the effect of a reduced envelope mass on the value of λ.
Publisher: Oxford University Press (OUP)
Date: 17-07-2014
Publisher: Cambridge University Press (CUP)
Date: 2008
DOI: 10.1071/AS08002
Abstract: In 2007 the field of nuclear astrophysics celebrated its 50th birthday.
Publisher: Oxford University Press (OUP)
Date: 08-12-2015
Publisher: Cambridge University Press (CUP)
Date: 2008
DOI: 10.1071/AS08005
Abstract: Recent work has proposed that a merger event between a red-giant and a He white dwarf may be responsible for the production of R stars (Izzard, Jeffery & Lattanzio 2007). We investigate the proposed evolution and nucleosynthesis of such a model. We simulate the hypothesized late ignition of the core flash by increasing neutrino losses until ignition occurs sufficiently far from the centre that the subsequent evolution produces carbon dredge-up to the extent that the post-flash object is a carbon star. Detailed nucleosynthesis is performed within this approximation and we show that the overall properties are broadly consistent with the observations. Details will depend on the dynamics of the merger event.
Publisher: CSIRO Publishing
Date: 1992
DOI: 10.1071/PH920559
Abstract: We review some of the difficulties associated with understanding star formation, and discuss some numerical approaches. In particular we describe a method which seems to hold promise for future studies.
Publisher: American Astronomical Society
Date: 10-11-2004
DOI: 10.1086/424559
Publisher: Springer Netherlands
Date: 2001
Publisher: Wiley
Date: 27-09-2012
Publisher: EDP Sciences
Date: 10-05-2007
Publisher: EDP Sciences
Date: 09-2013
Publisher: Elsevier BV
Date: 08-1997
Publisher: EDP Sciences
Date: 24-05-2012
Publisher: Wiley
Date: 09-2016
Abstract: Stellar models provide a vital basis for many aspects of astronomy and astro‐physics. Recent advances in observational astronomy – through asteroseismology, precision photometry, high‐resolution spectroscopy, and large‐scale surveys – are placing stellar models under greater quantitative scrutiny than ever. The model limitations are being exposed and the next generation of stellar models is needed as soon as possible. The current uncertainties in the models propagate to the later phases of stellar evolution, hindering our understanding of stellar populations and chemical evolution. Here we give a brief overview of the evolution, importance, and substantial uncertainties of core helium burning stars in particular and then briefly discuss a range of methods, both theoretical and observational, that we are using to advance the modelling.
Publisher: American Institute of Physics
Date: 2008
DOI: 10.1063/1.2905570
Publisher: ASCE
Date: 1997
DOI: 10.1063/1.53325
Publisher: American Astronomical Society
Date: 10-04-2008
DOI: 10.1086/529024
Publisher: Oxford University Press (OUP)
Date: 04-2002
Publisher: American Astronomical Society
Date: 20-02-2009
Publisher: American Astronomical Society
Date: 12-1991
DOI: 10.1086/170821
Publisher: EDP Sciences
Date: 13-05-2009
Publisher: Oxford University Press (OUP)
Date: 23-08-2004
Publisher: Oxford University Press (OUP)
Date: 13-12-2018
Publisher: EDP Sciences
Date: 06-2009
Publisher: Cambridge University Press (CUP)
Date: 2018
DOI: 10.1017/PASA.2018.42
Abstract: Getting a better understanding of the evolution and nucleosynthetic yields of the most metal-poor stars ( Z ≲ 10 −5 ) is critical because they are part of the big picture of the history of the primitive universe. Yet many of the remaining unknowns of stellar evolution lie in the birth, life, and death of these objects. We review stellar evolution of intermediate-mass Z ≤ 10 −5 models existing in the literature, with a particular focus on the problem of their final fates. We emphasise the importance of the mixing episodes between the stellar envelope and the nuclearly processed core, which occur after stars exhaust their central He (second dredge-up and dredge-out episodes). The depth and efficiency of these episodes are critical to determine the mass limits for the formation of electron-capture SNe. Our knowledge of these phenomena is not complete because they are strongly affected by the choice of input physics. These uncertainties affect stars in all mass and metallicity ranges. However, difficulties in calibration pose additional challenges in the case of the most metal-poor stars. We also consider the alternative SN I1/2 channel to form SNe out of the most metal-poor intermediate-mass objects. In this case, it is critical to understand the thermally pulsing Asymptotic Giant Branch evolution until the late stages. Efficient second dredge-up and, later, third dredge-up episodes could be able to pollute stellar envelopes enough for the stars to undergo thermal pulses in a way very similar to that of higher initial Z objects. Inefficient second and/or third dredge-up may leave an almost pristine envelope, unable to sustain strong stellar winds. This may allow the H-exhausted core to grow to the Chandrasekhar mass before the envelope is completely lost, and thus let the star explode as an SN I1/2. After reviewing the information available on these two possible channels for the formation of SNe, we discuss existing nucleosynthetic yields of stars of metallicity Z ≤ 10 −5 and present an ex le of nucleosynthetic calculations for a thermally pulsing Super-Asymptotic Giant Branch star of Z = 10 −5 . We compare theoretical predictions with observations of the lowest [Fe/H] objects detected. The review closes by discussing current open questions as well as possible fruitful avenues for future research.
Publisher: American Astronomical Society
Date: 10-12-1996
DOI: 10.1086/178152
Publisher: American Astronomical Society
Date: 11-12-2019
Publisher: American Astronomical Society
Date: 30-03-2012
Publisher: American Astronomical Society
Date: 12-1989
DOI: 10.1086/168189
Publisher: Oxford University Press (OUP)
Date: 19-07-2018
Publisher: Springer New York
Date: 2004
Publisher: Oxford University Press (OUP)
Date: 21-01-2010
Publisher: Springer Science and Business Media LLC
Date: 29-05-2013
DOI: 10.1038/NATURE12191
Abstract: The asymptotic giant branch (AGB) phase is the final stage of nuclear burning for low-mass stars. Although Milky Way globular clusters are now known to harbour (at least) two generations of stars, they still provide relatively homogeneous s les of stars that are used to constrain stellar evolution theory. It is predicted by stellar models that the majority of cluster stars with masses around the current turn-off mass (that is, the mass of the stars that are currently leaving the main sequence phase) will evolve through the AGB phase. Here we report that all of the second-generation stars in the globular cluster NGC 6752--70 per cent of the cluster population--fail to reach the AGB phase. Through spectroscopic abundance measurements, we found that every AGB star in our s le has a low sodium abundance, indicating that they are exclusively first-generation stars. This implies that many clusters cannot reliably be used for star counts to test stellar evolution timescales if the AGB population is included. We have no clear explanation for this observation.
Publisher: Oxford University Press (OUP)
Date: 02-2003
Publisher: Cambridge University Press (CUP)
Date: 08-2013
DOI: 10.1017/S1743921313014749
Abstract: Standard models of low-mass core helium burning stars typically give an asymptotic l =1 g-mode period spacing well below that inferred from observed mixed modes. We find that most physical uncertainties, such as mixing beyond the fully convective core, are not significant enough to be responsible for such a discrepancy. The solution to the problem may lie in a deviation of structure away from its canonical form, such as a more massive H-exhausted core, which we briefly explore here.
Publisher: Oxford University Press (OUP)
Date: 19-07-2018
Publisher: American Astronomical Society
Date: 15-11-2012
Publisher: Elsevier BV
Date: 07-2005
Publisher: Oxford University Press (OUP)
Date: 04-2015
DOI: 10.1093/MNRAS/STV612
Publisher: American Astronomical Society
Date: 15-11-2011
Publisher: Oxford University Press (OUP)
Date: 28-11-2014
Publisher: Oxford University Press (OUP)
Date: 14-01-2016
Publisher: American Astronomical Society
Date: 06-08-2018
Start Date: 2003
End Date: 12-2005
Amount: $270,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2010
End Date: 12-2013
Amount: $389,000.00
Funder: Australian Research Council
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Funder: Australian Research Council
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End Date: 12-2003
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Funder: Australian Research Council
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End Date: 12-2015
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Funder: Australian Research Council
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End Date: 12-2005
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Funder: Australian Research Council
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Funder: Australian Research Council
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End Date: 12-2005
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Funder: Australian Research Council
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Funder: Australian Research Council
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Funder: Australian Research Council
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End Date: 12-2009
Amount: $350,000.00
Funder: Australian Research Council
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