Martin Asplund

1
Lithium isotopic abundances in the first stars

• Martin Asplund
• Jorge Melendez

David Lambert Poul Erik Nissen Francesca
Primas Verne Smith
2
Motivation

• Lithium isotopes very useful
• Big Bang nucleosynthesis
• Cosmic ray physics
• Stellar structure and evolution
• Galaxy formation and evolution

3
Method
Isotopic shift in Li I 670.8nm resonance line
Exceptionally high-quality spectra needed
4
Observations
S/N450-1000 R90,000-150,000Sn

• VLT/UVES
• 6.5 nights
• 24 stars
• -3
• Asplund et al. (2006)

• Gemini/bHROS
• 6 nights
• 6 stars
• -3
• Smith et al.

• Keck/HIRES
• 4 nights
• 10 stars
• -3.3
• Asplund Melendez

5
Analysis
Model atmospheres 1D hydrostatic and 3D
hydrodynamical
Stellar parameters Teff H? line and colours log
g Hipparcos parallaxes Fe/H Fe II lines
6
Line broadening
1D rotation and macro-/microturbulence 3D
rotation Fe I, Fe II, Na I, Mg I, K I, Ca I, Sc
II, Ti II, Cr I lines
3D
1D
7
Li I 670.8nm line
Rotation, micro-/macroturbulence and instrumental
broadening fixed 7Li abundance, 6Li/7Li,
continuum level and wavelength shift free
parameters
8
6Li/7Li ratio
Errors from S/N, line broadening and stellar
parameters included
??2
9
6Li detections from Keck

• Excellent agreement for HD84937 and HD140283
  with Smith et al. (1993, 1998), Cayrel et al.
  (1999), Aoki et al. (2004) and Asplund et al.
  (2006)
• Same 6Li/7Li in 3D and 1D

6Li detections at Fe/H
10
6Li results from VLT and Keck

• Twelve 2? detections but many 1? results
• Most stars have 6Li/7Li ? 0.01?
• Or systematic errors?

11
Two cosmological Li problems
Keck
VLT
Nissen et al. (1999)
GCR (Prantzos 2006)
12
Two cosmological Li problems
With standard Li depletion
Keck
VLT
Nissen et al. (1999)
Note 7Li depletion 0.5 dex implies 6Li
depletion 1 dex
13
Possible 6Li production sites

• Stellar flares
• Cosmological cosmic rays
• Non-standard Big Bang nucleosynthesis

14
6Li production Stellar flares
Rotation convection ? magnetic activity ? 6Li
Tatischeff Thibaud (2007) LX5,000 LX,o for 1
Gyr ? log 6Li 1.0 as observed

• Problems
• No rapid rotation or magnetic activity in halo
  stars
• How does 6Li end up in photosphere?

15
6Li production Pop III stars

• Rollinde et al. (2005, 2006, 2007)
• Cosmic ray acceleration from Pop III supernovae
• SFR(z), top-heavy IMF, z10 reionization
• 6Li production

-10

• Problems
• Energetically possible?
• Fe and O enrichment?

-12
Rollinde et al. (2007)
-14
-10
-20
16
6Li production BBNS

• Supersymmetric particles like gravitino, stau and
  neutralino can modify BBNS
• Annihilation
• Decay
• Reaction rates

Jedamzik (2007)
6Li production
Problem Unproven physics
6Li production 7Li destruction
Jedamzik (2004, 2006, 2007), Kawasaki et al.
(2006), Cyburt et al. (2006), Pospelov (2007),
Bird et al. (2006)
17
Summary

• Two cosmological lithium problems
• 7Li inconsistent with Big Bang nucleosynthesis
• 6Li inconsistent with Galactic cosmic ray
  production

Extraordinarily challenging observations and
analysis
18
Happy half-century John!