# Presentation: 090115

##  Galactic LiBeB  Origin and EvolutionR. Ramaty -NASA/GSFC

- Stable isotopes: 6Li, 7Li, 9Be, 10B, 11B
- Most of the 7Li from BBN, AGB stars, novae and type II SNe
- About 20% of the 11B from type II SNe
- All the rest - produced by cosmic rays
- Spallation of C, N, O
-  + 4He  6Li, 7Li; 3He + 4He  6Li

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## Cosmic Ray Origin Models

- Acceleration: SN shocks, ~1050 erg/SN, i.e. 10% of the ejecta kinetic energy
- Source material that is accelerated in dispute:
- Gas and dust with average ISM composition
- Gas and dust from relatively fresh SN ejecta accelerated in superbubbles
- Hot ISM, formed by superbubble mergers, the likely site of cosmic ray acceleration, could have metal abundances dominated by SN ejecta

## Evolutionary Calculations          two models

**CRI** (cosmic rays interstellar), the cosmic ray source composition evolves as the ISM
**CRS** (cosmic ray superbubble), the cosmic ray source composition throughout all the evolution remains the same as that of the current epoch cosmic rays
- For both models the cosmic ray energy spectrum (power law in momentum) and energy/SN (~1050erg) do not evolve and are the same for core collapse (II, Ib/c) and thermonuclear (Ia) SNe

## Ambient Medium Abundance Evolution

- For -4<[Fe/H]<0
- He/H slowly evolving from 0.08 to 0.1
- [C/H]=[Fe/H], i.e. C/Fe=const, because at early times both C and Fe from massive stars and at later times C production by intermediate mass stars is compensated by Fe production from type Ia SNe
- [N/H]=[Fe/H] for simplicity
- Debate on the behavior of O at low [Fe/H]; full evolutionary calculations

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## Evolutionary Calculation

- One reservoir - primordial gas accumulation on 2 time scales, H=10Myr, d=5Gyr
- IMF, star formation, gas removal, stellar lifetimes, returned gas
- Fe,O production by SNII -- **WW95 and TS98**;  Fe by SNIa -- scaled to SNII for [Fe/H]>-1
- Possible delays, incorporation into high velocity dust-- Fe(mix)=0 or 30Myr; O(mix)=0 or 1Myr
- Calculate [O/Fe] vs. [Fe/H]; two limiting cases:                           **WW95(mixing); TS(no mixing)**

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## Be Evolution for CRS & CRI

- Wcr = 1050 erg/SN for SNII and SNIa
- CRI - all SN use Q/W(CRI)
- CRS - 85% of SNII and 50% of SNIa in superbubbles - use Q/W(CRS); 15% SNII and 50% SNIa use Q/W(CRI)
- Delayed Be deposition due to cosmic ray transport - tens of millions of years for nH=0.1 cm-3
- Calculate H,Fe,O,Be as functions of time; plot Be/H vs. Fe/H and O/H

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## CONCLUSIONS so far

- CRI, i.e. cosmic rays accelerated out of the average ISM, severely underpredicts the Be data, the increase in [O/Fe] notwithstanding
- Cosmic rays should be accelerated out of SN enriched material as in the CRS model, by shocks of successive SNe in superbubbles
- That the same energy per SN, ~1050 erg, is needed for the Be production as the value found from current epoch cosmic ray data and SN statistics provides strong support for the CRS model

## Current epoch cosmic rays CRI or CRS?

- Meyer, Drury, Ellison showed that with the preferential acceleration of refractories (Mg, Al, Si, Ca, Fe, Ni) and the A/Q dependence of the acceleration of volatiles  (H,He,Ne,Ar) in the well-mixed, warm ISM, the cosmic ray source abundances are consistent with solar abundances. **This supports the CRI model, but is in conflict with the Be evolution.**
- Acceleration of supernova ejecta in superbubbles (SB), including high velocity dust, also yields agreement between cosmic ray source and solar abundances.
- Most SNII are in SBs, and also a significant fraction of SNIa’s because of the large filling factors of the SB.
- The metallicity of the SB could be dominated by SN ejecta.
- A/Q does not work in the 106K SB, but mass dependent scattering of ambient atoms by the fast SN grains can achieve the A dependent enrichment of the cosmic ray volatiles vs. solar abundances.
**Thus, CRS is a good possibility for current epoch cosmic rays and is consistent with the Be evolution.**

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## The Hybrid CRI+LECR Model

- The possible existence of LECRs remains. They could be metal enriched by being accelerated in SBs as the CRS cosmic rays. A hybrid CRI+LECR model could be a solution to the Be evolution problem with CRI.
- This LECR paradigm was motivated by the reports of nuclear gamma ray lines from Orion. These data were retracted. Thus there is no information that would support (or negate) the existence of LECRs.
- Awaiting more sensitive gamma ray observation, we  consider the CRI+LECR model, in which the 2 cosmic ray components coexist, with the LECRs having the CRS composition independent of [Fe/H].

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## The Reaction 3He+4He6Li+p Induced by Fast 3He

- In solar flares this reaction produces enough 6Li to account for measurements in lunar soil where there is a solar wind implanted component (Chaussidon & Robert). The fast 3He result from preferential gyroresonant acceleration due to plasma turbulence. In our calculations (Ramaty et al., ApJL, in press, all the flare produced 6Li is evacuated by the solar wind.

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## Li-6 from Post BBN Era

- The reaction 3He+4He6Li+p, and its mirror 3H+4He6Li+n, might play a role here too (Jedamzik, PRL, 84, 3248, 2000). The fast 3He and 3H (several MeV/nucl) result from the photo-disintegration of 4He by gamma rays from the decays of relics left over from the BB. Jedamzik points out that the 6Li data sets more stringent constraints on the relics than do the 2H and 3He, and that 6Li produced in the post BBN era might explain the early Galactic 6Li data.

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## CONCLUSIONS

- Be requires acceleration from fresh SN ejecta
- CRI, aka standard GCR, does not work, increase in [O/Fe] notwithstanding
- Cosmic ray data consistent with CRI and CRS
- LECR could make CRI consistent with the Be data
- CRS and LECR accelerated in superbubbles
- Gammas, B/Be and 11B/10B to prove LECR existence
- 6Li at [Fe/H]<-2 suggest extragalactic origin, production by 3He and 3H associated with the decay or relics