Light Element Nucleosynthesis:The Li-Be-B StoryJake VanderPlasPhys 554 – 12-6-2007Mz3: Hubble Heritage ImagePresentation Summary• The Problem of Light Elements• Big Bang Nucleosynthesis• Cosmic Ray Nucleosynthesis• Supernova Nucleosynthesis• The Field NowElemental AbundancesLi Be BFeP554 class notesCWhere are the light elements?(Burbidge et al 1957)• Noted that D, 6Li,7Li, 9Be, 10B, 11B arefragile enough to bedestroyed in stellarinteriors• Posited “x-process”– a low-density,low-temperaturenucleosyntheticprocessPrantzos 2007Stellar Processes?• Stellar burning bypasses LiBeB with triple- process• Conditions in stellar interior favordestruction of LiBeBBig Bang Nucleosynthesis7Li6Li11B9Be10BVangioni-Flam 199910 orders ofmagnitude!From standardBBN model…Fields&Olive 1999Spite Plateau:Evidence of primordialorigins of 7LiMetallicity is a tracer of age:[Fe/H] = log(Fe/H) - log(Fe/H)solarNo PrimordialAbundanceFields&Olive 1999Spite Plateau:Evidence of primordialorigins of 7LiMetallicity is a tracer of age:[Fe/H] = log(Fe/H) - log(Fe/H)solarNo PrimordialAbundanceNo – it’s OK (Richard 2005)Discrepancy with BBN?• Light elements not from BBN (except 7Li)• Light elements not from stellar burning• So they must come from galactic processes– Cosmic Rays– Supernovae– Neutrino processesWhat is the x-process?Cosmic Ray Nucleosynthesis• Cosmic rays are enrichedwith Li-Be-B• ~5 orders of magnitudemore enriched than ISMPrantzos 2007Possible Sources of thisAbundance• Supernovae– more on this in a bit• Cosmic ray interaction with ISM– Spallation– Inverse SpallationCosmic ray Spallation• Cosmic ray particles interact with CNO inISM to produce light elements•This is a metallicity dependent“secondary” process – it depends on theamount of CNO in the ISMP, CNOLi-Be-B + smallerproductsSecondaryProcess?• Be/H and Be/H appear roughlylinear with Fe/H, which doesn’tmatch predictions• GCR more energetic in past?Probably not (Ramaty et al1997)• Galaxy more “leaky” nowthan in the past? Probablynot (Prantzos et al 1993)• CNO/Fe higher in the past?Very Possible (Boesgaard et al1999, Fields et al 1999)• Stellar primary source?Possibly for B, not for Be(Woosley et al 1990)Fields&Olive 1999],,[)(ONCNEdtLiBeBdGCRInverse Spallation• C,N,O,H accelerated by supernovae reactswith interstellar H & He, breaks apartCNOHe/HLi-Be-B + smallerproductsLi-Be-BInverse Spallation• Primary source if CNO abundance in GCRis constant with timeQuestions:Is this a good assumption?Where do these energetic CNO come from?“Superbubbles”• GCRs contain no 59Ni (half life ~ 105 years)– Secondary acceleration? Timescale betweensupernovae is ~ 105 years (Prantzos 2007)– Supermassive stars? Quick evolution meansless heavy elements end up in stellar windsSupernova Nucleosynthesis•11B had been thought to havebeen produced by 12C(,) atsupernova shock fronts(Dearborn 1989).• Neutrinos produced in core-collapse supernovae could besufficient to break apartnuclei in the Carbon shell(Woosley et al 1990)• Process described in detail inclass notes – I won’telaborate hereHHeCONeFeMgSiExplosion ModelsWoosley & Weaver 1995 – incorporated neutrinoprocesses in detailed explosion models – found Beoverproduced by a factor of 2. Other models predict asmuch as a factor of 5. 11B/Be ~ 4 for ISM (Olive et al 1994)Neutrino TemperatureEffectsEnergy Range fromtypical neutron star massWoosley & Weaver1995 calculationT=8MeVLower neutrino temperatureleads to smaller weak-current interaction cross-section.6 MeV fits observationsYoshida et al 2004Production range fromabundance measurements andGalactic evolution modelsSources of Li-Be-B• Big Bang Nucleosynthesis7Li (trace of others)• Stellar Nucleosynthesis7Li?• Supernova Nucleosynthesis 11B 7Li– “Normal” processes:– Neutrino effects:• Cosmic ray Nucleosynthesis 6,7Li 10,11B 9Be– Spallation– Inverse SpallationWhat we can learn from Li-Be-BAbundances• B from measurements of 7Li in low-metallicity halo stars(Fields et al 2005)• Spite plateau + BBN models are evidence for of Big Bang(Spite & Spite 1982)• Mixing lengths in stellar atmospheres (7Li discrepancies)• Asplund plateau – 6Li from exotic heavy particle decay?(Jedamzik 2004) Pop III star ages? (Prantzos 2007)• Neutrino spectrum in core-collapse supernovae (Yoshidaet al 2004)• Constraints on neutrino oscillations (Yoshida et al 2006)RemainingMysteries/Disagreements• “Asplund plateau” of 6Li in metal-poor starschallenges standard BBN• O/Fe~1?: Primary vs. secondary slope• Source of heavy GCRs• Correct mixture of processes?Asplund et al 2006ReferencesAsplund, M. et al 2006, ApJ 644, 229Burbidge, M. et al 1957, Rev. Mod. Phys. 29, 547Boesgaard, A. M et al 1999, AJ, 117, 492Dearborn D. et al 1989, ApJ 347, 455Fields B.D. & Olive K.A. 1999, ApJ 516, 797Fields B.D. et al 2005 ApJ 623, 1083Jedamzik, K. 2004, Phys Rev D 70, 063524Olive K.A. et al 1994, ApJ 424:666Prantzos N. et al 1993 ApJ 403,630Prantzos N. 2007, SSRv 130, 27Ramaty R. et al 1997, ApJ 488, 730Richard O. et al, 2005, ApJ 619, 538Spite, M., Spite, F., 1982, A&A 115, 357Vangioni-Flam E. & Casse M. 1999, ASS 265, 77Woosley S.E. et al. 1990 ApJ 356,272Woosley S.E. & Weaver T.A. 1995 ApJS 101,181Yoshida T. et al. 2004 ApJ 600,204Yoshida T. et al 2006 ApJ [astro-ph/0606042]Prantzos 2007 (based on Ramaty1997) – necessary GCR energyincrease to change Be/Fe andLi/Fe