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AGB Star Yields for Everyone

AGB Star Yields for Everyone. John Lattanzio 1 and Amanda Karakas 2 1: Centre for Stellar and Planetary Astrophysics, Monash University,Australia 2: Origins Institute, Department of Physics & Astronomy, McMaster University , Canada. Structure of Talk.

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AGB Star Yields for Everyone

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  1. AGB Star Yields for Everyone John Lattanzio1 and Amanda Karakas2 1: Centre for Stellar and Planetary Astrophysics, Monash University,Australia 2: Origins Institute, Department of Physics & Astronomy, McMaster University , Canada

  2. Structure of Talk • Reminder of AGB stars and vital role • Outline of what we want • What we can do • What we cannot yet do • State of the art models • Synthetic AGB models • Strengths and weaknesses • Best yields available now (and soon) • Distribution

  3. Public Speaking for Scientists Attention Time

  4. Not this one… Trivia Question 1 • Who said: “To the extent that its possible, it’s the isotopes that keep the theorists honest.” • Dave Arnett (U Arizona)

  5. S-process elements

  6. Massive stars produce most of the galactic magnesium, which is primarily 24Mg at low Z But 3 - 6 Msun AGB stars can produce large amounts of the heavy magnesium isotopes (Y. Fenner, A. Karakas, B. Gibson, J. Lattanzio)

  7. AGB stars are needed to recover the observed 25,26M/24Mg ratios at low metallicity Limongi et al. (2002) calculations generate more 25,26Mg thanWoosley & Weaver (1995) (Y. Fenner, A. Karakas, B. Gibson, J. Lattanzio, PASA, 2003)

  8. GCE of 19F – Renda et al (2003) x = Milky Way = LMC SN, WR and AGB = w Cen SN & WR SN only

  9. 23Na 22Ne 23Na 14N 23Na 22Ne Sodium 12C Note: some 23Na is primary and some is secondary!

  10. AGB star nucleosynthesis • Note the interplay of H and He burning… • Note the dependence on mixing regions… • Note that the return depends on mass-loss • Note that these are not the most precise inputs to the models…

  11. Trivia Question 2 • What is the original definition of a SHIP? • A three masted sailing vessel with square-rigging on all three masts Barque Brig

  12. What do we want? • Quantitative predictions of surface abundances over time for all M and compositions • Is this too much to ask???

  13. Something Like This – but as f(time)

  14. Something Like This – but as f(time)

  15. Trivia Question 3 • Which famous (Italian) stellar astronomer said: “We provide evolutionary tracks, yields and physics from the pre-main sequence through to the thermally pulsing AGB. Its certainly wrong, but its freely available.” • Alessandro Chieffi

  16. So why can’t we do it? • Well we can, but… • Each star takes a lot of cpu. • Typical AGB star (with my code) takes between 2 days and 4 weeks depending on the mass, mass-loss, and nucleosynthesis • There are many uncertainties…

  17. Main Problems • Mass-loss • Rate determines when AGB ends • Hence huge effect on yields • Dredge-Up • Remains hard to do properly • Surely its hydrodynamic… • Convective borders and overshoot? Supernovae have the Mass-Cut...

  18. How to Calculate Dredge-Up? • Depends on how you apply Schwarzschild …. some apply it naively and get NO dredge-up! • We search for a neutral point… a bit like overshooting… • Depends on how you implement it…

  19. Convection: mostly affects dredge-Up

  20. Calculating Dredge-Up No dredge-up Results depend on how you mix and iterate Deep dredge-up

  21. Convection: Dredge-Up • Its not simple • Its not one-dimensional • Its not static • Its not mixing-length • But it is very very hard to calculate…

  22. Convective Boundaries Eg Herwig and O… This will alter yields!

  23. Trivia Question 4 • Who said: “The ultimate goal of nuclear physics is to produce dust.” • Erwin Sedlmayr (Has his own brewery in Berlin…)

  24. The Best on Offer? • Best are full, detailed models • Star by star… • From ZAMS to end of AGB… • With the best you can do for all the physics… • One star per node on large cluster • Elements considered usually stop before the s-process…

  25. Amanda Karakas’ Thesis • Three compositions • Solar, LMC and SMC (Z=0.02, 0.008, 0.004) • Since then has added Z=0.0001 • Many masses • M=1.5 to 7 • Various bits published but not all  • Contact Amanda for yields…

  26. Other Full Model Yields • Herwig (2004) Z=0.0001, M=2 to 6 • Simon Campbell (in Fenner et al 2004) • Globular Cluster chemical evolution • M=1.25 to 6.5 • [Fe/H]=-1.4 and mix from Big Bang and SN • Ie “Z” = 0.0017 (Z=1-X-Y is not proportional to Fe) • Ventura et al (2002) • Different theory of convection (FST, not MLT) • M=3 to 6 (HBB range) • Z=0.0002 to 0.01 (5 values)

  27. Serious Advantage of Full Models • The interplay between HBB and TDU • Which ends first? • Unknown until we made some full detailed models go all the way to end of AGB • Has large effect on final envelope composition

  28. Trivia Question 5 • Who were described by Ned Kelly as: “…big, ugly, fat-necked, wombat-headed, fat-bellied, magpie-legged, narrow-hipped, splay-footed sons of Irish bailifs or English landlords…” • The Victorian Police Force

  29. The Other/Older Approach: Synthetic AGB Models • AGB stars are complicated • AGB stars take a long time to compute • But Paczynski noted that the surface L varied very nearly linearly with core mass • …at least for lower masses…

  30. Core-mass v Luminosity L/L = 59250(Mc/M – 0.5)

  31. Other relations can be fitted… • Mass in intershell convection zone • Duration of intershell convective zone • Interpulse period • Etc • Entire population can be synthesized very quickly!

  32. Synthetic AGB Models • But only as good as the inputs • And things are not simple really • Eg dredge-up law does depend on the envelope mass as well as the core and composition • There is “memory” of the earlier life of the star, at some level

  33. Not easy to know when to include Depends on M and Z Some turn it “on” at specific M and Z But what T? What rho? How much mass is burning? Very hard… The Biggest Problems? Hot Bottom Burning Dredge-Up • Can fit the dredge-up parameter l as a function of everything • But that has to come from detailed models and is not known… • Beware of this!

  34. Advantages • Well suited to yields! • Quick! • Can change reaction rates quickly • Can investigate mass-loss dependence • In principle…very powerful • But limited by the inputs of course

  35. Synthetic Yields Beware!! • Long history, starting with • Renzini and Voli 1981 • DO NOT USE RENZINI & VOLI (1981)! • Many better yields around today! • Who? • Van den Hoek & Groenewegen (1997) • Marigo (2001) • Forestini and Charbonnel (1997) • Izzard et al (2004)

  36. Comparison of synthetic with detailed yields: 4He Black = Karakas (full) Blue = Izzard et al (syn) Red = Marigo (syn) Green = Forestini & Charbonnel (syn) Magenta = vdHG (syn) Cyan = Ventura (full) Big Variation...

  37. 12C 13C 14N Z=0.02 Z=0.02 Z=0.02 Z=0.008 Z=0.008 Z=0.008 Z=0.004 Z=0.004 Z=0.004

  38. New Synthetic Yields from Izzard • Rob Izzard worked very hard on this • Aim is to include binaries • They go to places that single stars do not • So simple fits will not work all the time • Good fits to (our) detailed models • Real nucleosynthesis in most cases • Fit T and rho and then do real burning

  39. Izzard Yields Synthetic = red Detailed = green

  40. Izzard Yields Massive stars too Red and green = full models Cyan and magenta = synthetic

  41. Huge number of extra parameters to do with binaries Includes mass accretion mass-loss mass transfer Add binary population as well

  42. 4.3 Population Synthesis H H 4He 4He 12C 12C 13C 13C

  43. 14N 14N 15N 15N 16O 16O 17O 17O

  44. 27Al 27Al 32S 32S 36Ar 36Ar 40Ca 40Ca

  45. Trivia Question 6 • Which WWII General said: “I can take care of the Germans, but I am not sure I can beat Montgomery and Eisenhower.” • George Patton Bonus: "If Ike stops holding Monty's hand and gives me the supplies I'll go through the Siegfried line like shit through a goose."

  46. What is the Best Now? • Full models are probably best • Monash group • Karakas, Campbell, Lattanzio etc • Ventura et al 2002 (limited mass range) • Herwig 2004 (Z=0.0001 only, and overshoot)

  47. Synthetic if you must…. • Izzard et al 2004 • Beware: gap for M=7 to 12 = SUPER-AGB • Online yield calculator: • http://www.ciqua.org/binaryyields/index.php • For single stars set second at M=0.1 and very wide 

  48. Izzard Online Yield Calculator

  49. Izzard Online Yield Calculator

  50. Izzard Online Yield Calculator

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