AGB Star Yields for Everyone

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
Trivia Question 1

• Who said
• To the extent that its possible, its 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 than Woosley 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
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 cant 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 (Z0.02, 0.008, 0.004)
• Since then has added Z0.0001
• Many masses
• M1.5 to 7
• Various bits published but not all ?
• Contact Amanda for yields

26
Other Full Model Yields

• Herwig (2004) Z0.0001, M2 to 6
• Simon Campbell (in Fenner et al 2004)
• Globular Cluster chemical evolution
• M1.25 to 6.5
• Fe/H-1.4 and mix from Big Bang and SN
• Ie Z 0.0017 (Z1-X-Y is not proportional to
  Fe)
• Ventura et al (2002)
• Different theory of convection (FST, not MLT)
• M3 to 6 (HBB range)
• Z0.0002 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
The Biggest Problems?
Hot Bottom Burning
Dredge-Up

• 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

• 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 principlevery 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
Z0.02
Z0.02
Z0.02
Z0.008
Z0.008
Z0.008
Z0.004
Z0.004
Z0.004
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
Add binary population as well

• Huge number of extra parameters to do with
  binaries
• Includes
• mass accretion
• mass-loss
• mass transfer

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 (Z0.0001 only, and overshoot)

47
Synthetic if you must.

• Izzard et al 2004
• Beware gap for M7 to 12 SUPER-AGB
• Online yield calculator
• http//www.ciqua.org/binaryyields/index.php
• For single stars set second at M0.1 and very
  wide ?

48
Izzard Online Yield Calculator
49
Izzard Online Yield Calculator
50
Izzard Online Yield Calculator
51
Izzard Online Yield Calculator
52
Trivia Question 7

• Which geologist/astronomer said
• The beauty of science is that nature will tell
  you when you are wrong. So will your colleagues,
  but they may not always be right!
• Jerry Wasserburg

Accepting Crafoord Prize in Geology, 1986, from
King of Sweden
53
What is in the pipeline?

• Project with Stan Woosley
• He runs Z0 supernovae
• Their yields are the initial composition for my
  AGB models and his massive models
• The yields from that run (plus earlier, plus Big
  bang) are the next generation
• After a few generations just go to scaled solar
• Full, detailed, consistent models
• With all their uncertainties ?

54
Publication and distribution

• Karakas contact her (copy of thesis)
• Campbell contact him (copy of thesis)
• All will appear on webpages eventually
• Izzard for calculating your own
• Contact him for a copy of his thesis

55
The End?
This is not the end...
...it is not even the beginning of the end...
...but it may be the end of the beginning.
56
More appropriate for a theorist
Man will occasionally
stumble over the truth,
but most times he will
pick himself up
and carry on...