A5058934310- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Nuclear physics research studies
- Astronomical and nuclear sciences
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Nuclear Physics and Applications
- Solar and Space Plasma Dynamics
- Scientific Research and Discoveries
- High-pressure geophysics and materials
- Neutrino Physics Research
- Spacecraft and Cryogenic Technologies
- Geophysics and Gravity Measurements
- Nuclear reactor physics and engineering
- Planetary Science and Exploration
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Superconducting Materials and Applications
- Fluid Dynamics Simulations and Interactions
- Atomic and Molecular Physics
- Radioactive Decay and Measurement Techniques
University of Victoria
2015-2024
Joint Institute for Nuclear Astrophysics
2015-2024
Michigan State University
2014-2024
University of Notre Dame
2008-2018
Exascale (United Kingdom)
2018
Molecular Sciences Software Institute
2018
Washington University in St. Louis
2015
University of Basel
2015
University of Turin
2010-2015
University of Chicago
2015
Stellar physics and evolution calculations enable a broad range of research in astrophysics. Modules for Experiments Astrophysics (MESA) is suite open source, robust, efficient, thread-safe libraries wide applications computational stellar A one-dimensional module, MESAstar, combines many the numerical modules simulations scenarios ranging from very low mass to massive stars, including advanced evolutionary phases. MESAstar solves fully coupled structure composition equations simultaneously....
▪ Abstract The current status of modeling the evolution and nucleosynthesis asymptotic giant branch (AGB) stars is reviewed. principles AGB have been investigated in recent years leading to improved refined models, for example with regard hot-bottom burning or third dredge-up. postprocessing s-process model yields quantitative results that reproduce many observations. However, these most other processes are intimately related physics stellar mixing. Mixing currently not well-enough...
The slow neutron capture process in massive stars (weak s process) produces most of the s-process isotopes between iron and strontium. Neutrons are provided by 22Ne(α,n)25Mg reaction, which is activated at end convective He-burning core subsequent C-burning shell. s-process-rich material supernova ejecta carries signature these two phases. In past years, new measurements cross sections beyond significantly changed predicted weak distribution. reason that variation Maxwellian-averaged (MACS)...
We update the capabilities of open-knowledge software instrument Modules for Experiments in Stellar Astrophysics (MESA). The new auto_diff module implements automatic differentiation MESA, an enabling capability that alleviates need hard-coded analytic expressions or finite difference approximations. significantly enhance treatment growth and decay convection MESA with a model time-dependent convection, which is particularly important during late-stage nuclear burning massive stars electron...
We provide a set of stellar evolution and nucleosynthesis calculations that applies established physics assumptions simultaneously to low- intermediate-mass massive star models. Our goal is an internally consistent comprehensive nuclear production yield data base for applications in areas such as pre-solar grain studies. non-rotating models assume convective boundary mixing where it has been adopted before. include 8 (12) initial masses $Z = 0.01$ ($0.02$). Models are followed either until...
We review the observed properties of extremely hot, hydrogen‐deficient post–asymptotic giant branch (AGB) stars spectral type [WC] and PG1159. Their H deficiency is probably caused by a (very) late helium‐shell flash or an AGB final thermal pulse, laying bare interior stellar regions that are usually kept hidden below hydrogen envelope. Thus, photospheric elemental abundances these allow us to draw conclusions about details nuclear burning mixing processes in precursor stars. summarize state...
We study the late evolution of solar metallicity stars in transition region between white dwarf formation and core collapse. This includes super-asymptotic giant branch (super-AGB, SAGB) stars, which ignite carbon burning form an oxygen-neon (ONe) core. SAGB star cores may grow to Chandrasekhar mass because continued H- He-shell burning, ending as core-collapse supernovae. From stellar models we find that initial range for is 7.5–9.25 M☉. perform calculations with three different codes judge...
We use three-dimensional hydrodynamical simulations to study the rapid infall phase of common envelope interaction a red giant branch star mass equal 0.88 \msun and companion ranging from 0.9 down 0.1 \msun. first compare results obtained using two different numerical techniques with resolutions, find overall very good agreement. then outcomes those observed systems thought have gone through envelope. The fail reproduce in sense that most donor remains bound at end final orbital separations...
Depending on mass and metallicity as well evolutionary phase, stars occasionally experience convective-reactive nucleosynthesis episodes. We specifically investigate the situation when nucleosynthetically unprocessed, H-rich material is convectively mixed with a He-burning zone, for example in unstable shell top of electron-degenerate cores AGB stars, young white dwarfs or X-ray bursting neutron stars. Such episodes are frequently encountered stellar evolution models extremely low zero metal...
[abridged] We study the s-process in AGB stars using three different stellar evolutionary models computed for a 3Msun and solar metallicity star. First we investigate formation efficiency of main neutron source. parametrically vary number protons mixed from envelope into C12 rich core. For p/C12 > 0.3, mainly N14 is produced, which represent major poison. The amount He intershell maximum value time-integrated flux are proportional. Then generate detailed calculations on basis constructed...
The stellar mass range 8 ≲ M/M☉ 12 corresponds to the most massive asymptotic giant branch (AGB) stars and numerous stars. It is host a variety of supernova (SN) progenitors therefore very important for galactic chemical evolution population studies. In this paper, we study transition from super-AGB (SAGB) star find that propagating neon–oxygen-burning shell common both electron capture (EC-SN) lowest iron-core-collapse (FeCCSN) progenitors. Of models ignite neon-burning off-center, 9.5 M☉...
The {\alpha}-formalism is a common way to parametrize the envelope interaction between giant star and more compact companion. {\alpha} parameter describes fraction of orbital energy released by companion that available eject star's envelope. By using new, detailed stellar evolutionary calculations we derive user-friendly prescription for {\lambda} an improved approximation binding energy, thus revising equation. We then determine both from simulations observations in self consistent manner....
The goal of this Letter is to analyze the impact a primary neutron source on s-process nucleosynthesis in massive stars at halo metallicity. Recent stellar models including rotation very low metallicity predict strong production 14N. Part nitrogen produced H-burning shell diffuses by rotational mixing into He core where it converted 22Ne providing additional neutrons for s-process. We present calculations 25 M☉ star [Fe/H] = –3, –4, about 0.8% mass made convective He-burning core. usual weak...
Context. The prediction of the spins compact remnants is a fundamental goal theory stellar evolution.
We provide here a significant extension of the NuGrid Set 1 models in mass coverage and toward lower metallicity, adopting same physics assumptions. The combined data set now includes initial masses M/Msun = 1, 1.65, 2, 3, 4, 5, 6, 7, 12, 15, 20, 25 for Z 0.02, 0.01, 0.006, 0.001, 0.0001 with alpha-enhanced composition lowest three metallicities. These are computed MESA stellar evolution code evolved up to AGB, white dwarf stage, or until core collapse. nucleosynthesis was calculated all...
Despite much effort in the past decades, C-burning reaction rate is uncertain by several orders of magnitude, and relative strength between different channels 12C(12C,alpha)20Ne, 12C(12C,p)23Na 12C(12C,n)23Mg poorly determined. Additionally, conditions a high 12C+12C may lead to lower central temperatures 13C(alpha,n)16O emerging as more dominant neutron source than 22Ne(alpha,n)25Mg, increasing significantly s-process production. This due rapid decrease 13N(gamma,p)12C with decreasing...
We present hydrodynamic simulations of the common envelope binary interaction between a giant star and compact companion carried out with adaptive mesh refinement code enzo smooth particle hydrodynamics phantom. These mimic parameters one by Passy et al. but assess impact larger, more realistic initial orbital separation on simulation outcome. conclude that for both codes post-common is somewhat larger amount unbound mass slightly greater when wide enough does not yet overflow or just...
We investigate the evolution of super-AGB thermal pulse (TP) stars for a range metallicities (Z) and explore effect convective boundary mixing (CBM). With decreasing metallicity along TP phase, He-shell flash third dredge-up (TDU) occur closer together in time. After some time (depending upon CBM parameterisation), efficient TDU begins while pulse-driven convection zone (PDCZ) is still present, causing exchange material between PDCZ envelope. This results ingestion protons into He-burning...
Based on stellar evolution simulations, we demonstrate that rapidly accreting white dwarfs in close binary systems are an astrophysical site for the intermediate neutron-capture process. During recurrent and very strong He-shell flashes stable H-burning accretion regime H-rich material enters flash convection zone. $^{12}$C(p,$\gamma)^{13}$N reactions release enough energy to potentially impact convection, i process is activated through $^{13}$C($\alpha$,n)$^{16}$O reaction. The H-ingestion...
We have found that at least seven hydrogen-deficient carbon (HdC) and R Coronae Borealis (RCB) stars, 16O/18O ratios close to in some cases less than unity, values are orders of magnitude lower measured other stars (the Solar value is 500). Greatly enhanced 18O evident every HdC RCB we cool enough detectable CO bands. The three < 1, any the stars. These discoveries important clues determining evolutionary pathways for which two models been proposed: double degenerate (white dwarf (WD)...
We present the first three-dimensional, fully compressible gas-dynamics simulations in 4π geometry of He-shell flash convection with proton-rich fuel entrainment at upper boundary. This work is motivated by insufficiently understood observed consequences H-ingestion post-asymptotic giant branch (post-AGB) stars (Sakurai's object) and metal-poor AGB stars. Our investigation focused on process top boundary subsequent advection H-rich material into deeper layers, we therefore ignore burning...
After off-center C ignition in the cores of super-AGB stars flame propagates all way down to center, trailing behind it C-shell convective zone, and thus building a degenerate ONe core. This standard picture is obtained stellar evolution simulations if bottom convection boundary assumed be discontinuity associated with strict interpretation Schwarzschild condition for instability. However, this prone additional mixing processes, such as thermohaline mixing. Using hydrodynamic we show that,...
We present a detailed analysis of the composition and nucleosynthetic origins heavy elements in metal-poor ([Fe/H]=-1.62+/-0.09) star HD94028. Previous studies revealed that this is mildly enhanced produced by slow neutron-capture process (s-process; e.g., [Pb/Fe]=+0.79+/-0.32) rapid (r-process; [Eu/Fe]=+0.22+/-0.12), including unusually large molybdenum ([Mo/Fe]=+0.97+/-0.16) ruthenium ([Ru/Fe]=+0.69+/-0.17) enhancements. However, not carbon ([C/Fe]=-0.06+/-0.19). analyze an archival...
Novae are cataclysmic variables driven by accretion of H-rich material onto a white-dwarf (WD) star from its low-mass main-sequence binary companion. New time-domain observational capabilities, such as the Palomar Transient Factory and Pan-STARRS, have revealed diversity their behaviour that should be theoretically addressed. Nova outbursts depend sensitively on nuclear physics data, more readily available nova simulations needed in order to effectively prioritize experimental effort...
We present the N, O, F, and Na abundance 12C/13C isotopic ratio measurements or upper limits for a sample of 10 C-rich, metal-poor giant stars: 8 enhanced in s-process (CEMP-s) elements 2 poor n-capture (CEMP-no). The abundances are derived from IR, K-band, high-resolution CRIRES@VLT obtained spectra. metallicity our ranges [Fe/H] = −3.4 to −1.3. F could be measured only two CEMP-s stars. With [F/Fe] 0.64, one is mildly F-overabundant, while other F-rich, at 1.44. For remaining eight...