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Transcript of THE MONASH CHEMICAL YIELDS - iau-fm7.stsci.eduiau-fm7.stsci.edu/programs/FM7-IAU-Doherty.pdfElement...
THE MONASH CHEMICAL YIELDS PROJECT (Mon ey)
Carolyn DohertyJ. Lattanzio, G. Angelou, S.W. Campbell,
R. Church, T. Constantino, S. Cristallo, P. GilPons, A. Karakas, M. Lugaro, R. Stancliffe
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Element productionLow and intermediate stars are important for galactic chemical evolution as they enrich the environment with C, N, F, and ~ ½ of all of the elements past Fe via the sprocess
Goal: to produce a large and homogeneous set of (single star) nucleosynthetic yields for low and intermediate mass stars
Overview* Low & intermediate mass star evolution (AGB stars)
* Evolution Code – Overview
* Nucleosynthesis Code overview
* Proton ingestion episodes
● * Our computational grid
* Low metallicity models
* Mon ey Online
* Summary & Conclusions
χ
AGB Star Recap Stars in the mass range ~ 0.8 – 10 Msun
After core H & He (& C) burning they enter the thermally pulsing AGB phase which consists of alternating H & He shell burning phases
Strong mass loss erodes the envelope to leave a CO (or ONe) white dwarf Lugaro 2005
TPAGB nucleosynthesis : Third dredge up events Hot Bottom burning
Evolution Program (MONSTAR)
Monash version of Mount Stromlo stellar program
Recent code developments
* Low temperature variable composition opacities from ÆSOPUS (Marigo & Aringer 2009 ) & updated equation of state to OPAL & Helmholtz (see Constantino et al. 2014).
* Refined carbon burning, updated electron screening & neutrino losses (Doherty et al. 2010)
* “Extramixing” non canonical mixing thermohaline (Angelou et al. 2011, 2012)
* Addition of species 7Be, 7Li, 13C for 13C (a,n)
Nucleosynthesis Program (MONTAGE)
Modified Monash nucleosynthesis code (Church et al. 2009)
A lower network to Ca Solves mixing and burning simultaneous
● Upper network (from Cristallo et al. 2009) is decoupled with 2 step
● *burn neutrons passed to network and then *mix.
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● Upper Network 1 – includes only neutron capture reactions and beta decays 389 species (475)
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● Upper Network 2 – 631 (717 total) species, inc. species further from beta stability – for very high neutron densities
Hybrid code is MUCH FASTER
Results compare very well with brute force method
Spatial coverageHow fine an initial mass spacing is required?
IMF Weighted yields (from our light element compilations)
Some isotopes are only produced in narrow mass range – we want to capture these peaks
~ 0.1, 0.25 or 0.5 Msun divisions
Doherty et al. 2014a (inc Karakas 2010)
Z =0.02Z=0.008Z=0.004
Initial Mass (Msun)
Metallicity coverageHow to choose which metallicities? e.g. * Presolar grains * Globular clusters * CEMP s stars (Fe/H 3.5 to 2)* First Stars Z=0 * Supersolar
Harris 1996
Busso et al. 2001
Proton ingestion episodes (PIEs)Campbell 2007
Low Z, low mass AGB stars Convective He burning region comes in contact with H rich regionProtons are ingested (PIE) where it has high temp and density Production of 13C from 12C and then activation of the 13C(a,n)16O neutron source e.g. Fujimoto et al. 1990,Lau et al. 2009 Campbell et al. 2008/10, Herwig 2011, Bertolli et al 2013 etcALSO Dredgeout event in massive SuperAGB stars
High neutron densities (~ 1015 n cm3 )
Doherty et al. 2015
s/r or i process nucleosynthesis
Stable isotopes
r-process code from Petermann et al. 20121-zone trajectories
i process path
Stable isotopes
s processr process
With the high neutron densities the abundances can venture far from beta stabilityiprocess (Cowen & Rose 1977)
PIE MODELS NEED OUR LARGER NETWORK
Met
allic
ity
Key areasHeavy element yield predictions for:
* SuperAGB stars
* LowZ AGB stars
* Supersolar Z stars
● * PIES
Extramixing (thermohaline)
Uncertainty parameter space
13C Pockets
Proton ingestion episodes (PIES)
We insert a partially mixed zone (PMZ) for 13C pocket
Uncertainties – parameter spaceAGB stellar modeling involve many uncertainties For the evolution, in particular the:
* Mass loss rate AGB phase RGB phase
* Mixing length theory value (MLT) of FST etc?Our standards * Reimers 1975 eta= 0.4 (RGB) and Vassiliadis and Wood 1993 (modified Wood 2007) (AGB)BUT test grids will be performed for a substantial subset
For the nucleosynthesis some main uncertainties are: * 13C pocket – size, which mass etc * Nuclear reaction rates
With the speed of our nucleosythesis calculations we can compute subgrids with different 13C pocket sizes, profiles to provide robust uncertainty bounds
Low metallicity AGB stars Update to the light element, low mass, low Z AGB star yields
Inclusion of low temp molecular opacity shortens duration of the TPAGB phase and reduces HBB temperatures
● Our preliminary calculations show greatly reduced 3DU/HBB products and also a quite different white dwarf mass distribution
Constantino et al. 2014 (+ works Marigo & collaborators)
Tem
pera
ture
(MK
)
Campbell & Lattanzio 2008
Monχey online – coming soon EVOLUTION
* Stellar tracks
* Thermally pulsing evolutionary properties
NUCLEOSYNTHESIS
* Surface compositions
* Internal chemical compositions
* Neutron densitiesYIELDS
* Stellar Yields
* Weighted element/isotopic yields scaled by a range of IMFs
* Uncertainty estimates for each element/isotope
AGB STAR TUTORIAL
PLOTTING INTERFACE
Summary and Conclusions● Low and intermediate mass star nuceleosynthetic calculations
and stellar yields have a large range of applications from Galactic Chemical evolution, presolar grain abundances, planetary nebula studies, CEMPs stars etc.
Computations for the Mon eyχ project are well underwayWe expect a release of the first results later this year
We are currently working on the web interface – any requests for functionality, or specific outputs are very welcome !
"Everybody's Got Something To Hide.... *EXCEPT* for me and my MonKey" John Lennon and Paul McCartney