Pre-solar Grains - University of Victoria

Pre-solar GrainsLearning from their isotopic signatures

Thursday, November 25, 2010

Stardust from Meteorztes18

Table 1.3 Infbrmation from presolar grains relating to their site otformation and their journey through space'

information

Meteor ' . . .

grains is an extremely precise 1''-site of formation and must be e:'::mixing in stars.

The composit ion of the Paler-. -- :ini t ial composit ion of the star al i -

- -- 'star i tself . The init ial composit- ' r- --star and the place where the stal" -' ' -chemical evoiut ion calculat ions. T---fecycl ing of matter represel l ter i . : -into new stars in which the matl ' - : ' -reactions, and from the stars ba'- ' ,- ' : --such studies is to follow the er-ol':: -regions of a galaxy and in matlr . ' l - :-( ompared with observatiotts c-t- -

and of the interstellar mediuui. 1-,ix' nucleosynthesis in the p&r!l l i :- -in presolar grains is beiieved to r'' -:tars, thus providing detailed c'-'1r>- - -'

Galaxy (see e.g. Sec. 4.6) '

The stel lar composit ion is frrr-- - :

r ing inside the star i tself . Thest :--composition and evolution&1'\' :-': --t ions are due to nuclear r!&ctir- ' l -- ' --

interiors. They depend crucia- '- ' --)tar and the effi.ciency of nuclea-l -' 'the different region of the stal al't --lar evolution, while nuclear I'eai' - -'or calculated theoreticalll-. TiL. '--g la ins show large var ia l iot t . ' l ' -their parent stars. The anah-=l. -

thermal structure of the stal ' : i l - - :In order for the nucleosvl l l l --- -

: t&r to be relevant Lo l l te c 'u:r- :tnuch cooler outer regiotts. . ' ' ' l l - ' ---that the processed material i : ' - :of the star. In red giant stat ' : - -(see Secs. 4.2. I and 4.3) becatt := - . -

stel lar mass is located and n-l t t l - - -

tion (fluid circulation). per.itl. i-

1.5 New information from presolar grains

When considering the different astronomical sites through which presolargrains journey, uJ r.pr"rented in Fig. I.2, iL is clear why these grains rep-resent not only a new fieid of urtron"onty, where dust from stars is analysedin the laboratory, but also a new scientific field requiring the common ef-fort of scientists from very different disciplines' These discipiines rangefrom nuclear physics, to theoretical astrophysics, observational astronomy'cosmochemistry and the laboratory analysis of materials' The informationthat we can extract from presolar grains is summarised in Table 1'3 andd,iscussed in the rest of this section'

Circumstel lar regions - initial composition of the star (Galactic

Chemical Evolution)- stellar thermal structure, nucleosynthests

and nuclear reaction rates

- mixing processes inside red giant stars.

and during nova and supernova exploslons- ptysical tnd ch"t"i"al properties of the gas

around stars

- destruction processes of cosmic dust

- exposure to Calact ic cosmic raYs

- cloud and grain chemistrY- survival of presolar mater ia l in the

Interstellar medium

Molecular cloud

Solar system

Meteorite

early solar sYstem

metamorPhit- Pto""t""t of -"t"ofu

l .S. lstel tareaolut ion,nucleosynthes' i 'so 'ndrni ' r ingThe very precise analysis of the isotopic composition of presoiar grains rep-resents a breakthrough in the field oi stelrar evorution and nucleosvnthesis.During the chemi.ul"pro."ss of formation of molecules and grains aroundstars, isotopic fractionation effects, i.e. preferences in incorporating dif-ferent isotopes of a given element' could have only prod'uced verY smallisotopic anomalier, ul u level of a few parts per thousand' Thus, the enor-mous range of variation in the isotopic compositions observed in presolar

What can we learn from pre-solar grains?

‣ As discussed in the “guest” lectures dust is everywhere

‣ dust grains carry signatures of their past history and constrain the physics processes involved in their formation, advection into the proto-solar cloud, the solar system formation along with the formation of the meteoritic parent body of the grains


Types of pre-solar grains

12 Stardust from Meteorites

Graphite and SiC grains also contain tiny subgrains of Ti, Zr, Mo,

Ru and Fe-carbides [29] as weil as subgrains of Fe-Ni metals [75]. AIso

polycyciic aromatic hydrocarbon (PAH) molecules have been found in many

graphite grains [187].

Presolar grains are all refractory, which means that, at high tempera-

tures, roughly between 1300 and 2000 K, they can condense directly from

the gas phase. The condensation sequence of minerals depends on the initial

composition of the gas, and indeed mainly on the C/O ratio. If CIO < I,

all the carbon is locked up in carbon monoxide (CO) molecules, which have

a very strong bond and are stable at high temperature, and the condensed

minerals are mostly oxides and silicates. If C lO > 1, instead, all the oxygen

is locked up in CO molecules and carbon compounds can condense, such as

graphite and carbides. Since in the solar system CIO - 0.4, carbon bearing

minerals could not have condensed in the protosolar nebula. Hence, these

types of meteoritic grains are virtually all of presolar origin.

Table 1.2 Types of presolar grains, abundance in the

Murchison meteorite f1321, and typical size.

type abundance (pp-) size (p,m)

!.4.L D'iarnonds

The most abundant presolar 3l::-r-:nanometers (10-e m). hence - ' ._-- . - :

are fat more abundant than clrr.,- - - 1--,

stitute almost 6% of the total rt.r:: .:

diamonds carry the exotic Xe-HL .:.

cleosynthesis 1270]. Since these r r. .

stars exploding as superno\-F. pr.> -:origin. The implications of t l i i- r-;presence of the Xe-HL compolrE: ., :

the only information from the :,.:-, .origin. However, this origin cai^ i,-,

-.of the diamond grains because .: =

so that only about one nanodia::- :-

anomalous Xe. Moreover. beca,;- -be analysed one by one, their ca:: -_,rnly in bulk, i.e. in collection. - -it is only possible to obtain dar: r_

mill ions of grains, which happer-= -

this does not necessarily mean ::,.-

oosition, because extreme coltn, :--_

ar-eraging process. The laNr'15\ :.-.-::

:he terrestrial value, but in agit-:_-_.

221] . As for noble gases in nre:-" :--.

lifferent components and the ir:-: -- "Ref. 113al.

The favoured mechanism f,r: :-= .

:'lentified in a chemical vapoul--rj:r :_.

. 'rre [78], by which material in a -. .:,.

:"eactions, rather than a high-p,:::---l

rroduced, for example, dianror,-: ,r--",-ith condensation in cooi stellr.:

----_{ases in the diamonds, ion implar-- ::-.

-,r ould also be consistent ri-ith rl-t : -

-

increases with the grain size -2!.

In summary, it is not knor..-r- t-__.

actually presolar. Some of thel.

' - , f the solar system f761. This r= -- . . t .

diamond

silicates

sil icon carbide (SiC) 9a

spinel (MSAIzO+) Ic

>750"_b

>2d

0.002

0.1 - 0.5

0.1 - 20

0.5

0.8 - 28

0.5-4

- l

graphite

corundum (AlzO:) -0.005"

si l icon ni t r ide (Si3N4) >0.002/

o Found and measured in - 40 chondritic meteorites.

Abundances vary with the matrix content and metamor-

phic degree of the meteorite.b Identified in the Acfer 094 and North West Africa 530

meteorites with contrasting abundance estimations of -

25 ppm [200], 30 ppm [199] and 75 ppm [194].

' Also identified in other chondritic meteorites such as

Murray, Orgueil and Acfer 094.d Also identified in nine other chondritic meteorites.

' Also identified in four other chondritic meteorites, with

abundance up to 0.2 ppm.

/ Inaccurately known, also identified in four other chon-

dritic meteorites.

Lugaro TB

Lodders & Amari (2005)

Diamonds:‣ nm size → C isotopic ratio only

measured in bulk‣ some carry Xe-HL component related to

p- and r-process → massive stars, from SN

‣ formation: chemical vapour-deposition-like process at low P consistent with origin in cool atmospheres (rather than high-pressure shock-induced metamorphism)

‣ still unknown which fraction pre-solar

Silicate grains: ‣ SiO and other Si-based minerals (e.g.

olivine [Mg, Fe]2SiO4

‣ not found until 2004 because more easily destroyed during the chemical separation phase and because small

Silicon carbide grains (SiC):‣ large (a few )→ analysis of single

grains possible0.1µm

high enough to make elemental abundance and isotopic measurements withreasonable precision.

The average size of SiC grains is !0.5 mm in the Murchison meteorite, with sizesranging up to 20 mm, but grains 410 mm are extremely rare. The size distribution ofSiC in different types of meteorites varies, e.g., the Murchison chondrite typically haslarger-sized SiC on average than other meteorites, for unknown reasons (Amari etal., 1994; Huss et al., 1997; Russell et al., 1997).

The morphology of most SiC grains extracted from meteorites by chemicalprocedures shows euhedral shapes with more or less pitted surfaces (Fig. 4a and b).In order to examine ‘‘pristine’’ SiC grains not subjected to chemicals, Bernatowicz etal. (2003) dispersed matrix material excavated from the interior of the Murchisonmeteorite onto polished graphite planchets and examined them by SEM. The pristinegrains have less surface pits than grains isolated by chemical procedures, indicatingthat etching of surface defect structures occurs during chemical isolation. Of the 81pristine grains studied by Bernatowicz et al. (2003), !60% are coated with anamorphous, possibly organic phase. No differences in morphology other than thosecaused by sample extraction procedures have been observed among SiC grains.

Synthetic SiC has several hundred different crystallographic modifications butpresolar SiC apparently only occurs in the cubic 3C and hexagonal 2H modificationand intergrowths of these two (Daulton et al., 2002, 2003). This limited polytypedistribution in presolar SiC suggests condensation of SiC at relatively low totalpressures in circumstellar shells (Daulton et al., 2002, 2003).

5.1.1. Chemical and isotopic compositions of ‘‘bulk’’ SiC aggregatesThe analyses of bulk samples have the advantage that data with high precision can

be obtained. This provides well-defined average properties for whole suites of

ARTICLE IN PRESS

Fig. 4. Secondary electron images of SiC grains from the Murchison meteorite. Larger grainssuch as these shown are relatively rare. Scale bars are 1 mm. (a) The pitted surface structure iscommon for SiC grains, and most likely due to the harsh chemical treatments during theextraction from meteorites. The 12C/13C ratio of this grain is 55 (cf. solar ¼ 89). (b) A SiCgrain with a smooth surface. The 12C/13C ratio of this grain is 39.

K. Lodders, S. Amari / Chemie der Erde 65 (2005) 93–166 107


Silicon carbide grains (SiC):‣ carry signature of s process (Xe-S)‣ carry the Ne-E(H) signature

associated with 22Ne

• Graphite grains

• Oxide grains‣ corundum:‣ spinel: ‣ Titanium oxide:

• Silicon nitride grains‣ requires C/O>1 ( )‣ SN orgin?

Al2O3

MgAl2O4

TiO2

Si3N4

searched for by ion imaging and then studied. The ‘‘true’’ distribution (by number) isnoted in the legends of Figs. 6 and 7, and in Table 5.

About 93% (by number) of presolar SiC are mainstream grains, with lower12C/13C and higher 14N/15N than the respective terrestrial reference ratios of12C/13C ¼ 89 and 14N/15N ¼ 272. Their Si-isotopic composition is slightly 29Si- and30Si-rich (29Si/28Si and 30Si/28Si are up to 1.2" solar). In the three Si-isotope plot,mainstream grains define a line with d29Si ¼ #15.9+1.31 d30Si (Lugaro et al., 1999).The fit parameters vary depending on the number of points included in theregressions, e.g., Hoppe et al. (1994) find d29Si ¼ #15.7+1.34 d30Si, and Nittler andAlexander (2003) obtained d29Si ¼ #18.3(70.6) +1.35(70.01) d30Si .

Grains with 12C/13Co10 and 14N/15N ¼ 40–12,000 are called A+B grains (Amariet al., 2001a). Originally, it was thought that two distinct populations ‘‘A’’ and ‘‘B’’existed, but these two belong to the same continuum spanned by C- and N-isotopes(Fig. 6). The Si-isotopes of A+B grains are similar to those of mainstream grains(Fig. 7). In the three Si-isotope plot, A+B grains define a line withd29Si ¼ –34.1(71.6)+1.68(70.03) d30Si (Amari et al., 2000b) with a small off-setin slope compared to the mainstream grains. The A+B grains are the second largestpresolar SiC population and constitute 3–4% of all SiC grains.

ARTICLE IN PRESS

Fig. 6. SiC grains fall into different populations based on their C- and N-isotope ratios(Alexander, 1993; Amari et al., 2001a–c; Hoppe et al., 1994, 1997,2000; Huss et al., 1997; Linet al., 2002; Nittler et al., 1995). For comparison, stellar data are plotted with error bars andtheir N-isotope ratios are typically lower limits (Wannier et al., 1991; Querci and Querci, 1970;Olson and Richer, 1979). The dotted lines indicate solar isotope ratios.

K. Lodders, S. Amari / Chemie der Erde 65 (2005) 93–166110


ARTIC

LEIN

PRESS

Table 5. Some characteristics of presolar silicon carbide populations

Designation Mainstream X Y Z A+Ba Nova

Crystal type 3C, 2Hb 3C, 2Hb 3C, 2Hb 3C, 2Hb 3C, 2Hb 3C, 2H?b

Heavy traceelementsc

!10–20" c Highly depleted !10" c NA Solar or 10–20" c NA

12C/13C 10–100 20–7000 140–260 8–180 o3.5 (A)3.5–10(B)

o10

14N/15N 50–2" 104 10–180 400–5000 1100–1.9" 104 40–1.2" 104 o2029Si/28Sic 0.95–1.20" 28Si-rich 0.95–1.15" Esolar 1.20" Esolar30Si/28Sic 0.95–1.14" 28Si-rich 30Si-rich 30Si-rich 1.13" 30Si-rich26Al/27Al 10#3–10#4 0.02–0.6 Similar to MS Similar to MS o0.06 Up to 0.4Other isotopicmarkersc

Excess in 46Ti,49Ti, 50Tiover 48Ti

44Ca excess41K excess




47Ti-rich

22Ned Yes NA NA NA NA NAAbundance (%) 87–94 1 1–2 0–3 2–5 $ 1

Sources: Amari et al. (2001a, b), Hoppe and Ott (1997), Hoppe and Zinner (2000), Nittler and Hoppe (2004a, b), Ott (2003), Zinner (1998).aGroup A and B grains were initially separated but later found to form a continuum in composition.bCubic 3C, hexagonal 2H; Daulton et al. (2002, 2003).cAbundance compared to solar composition.d 22Ne ¼ Ne–E(H) ¼ Ne(G); and NA: not analyzed.

K.Lodders,

S.Amari

/Chem

ieder

Erde65

(2005)93

–166109


Mainstream SiC grains




ARTICLE IN PRESS



Clues:‣ C-rich and dust-forming, s process → 3rd

DUP , evolved AGB stars

C and N isotopic signatures‣ start with abundance distribution at the

end of H-core burning before envelope convection forms

‣ then this signature will be mixed to the surface

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Mainstream SiC grainsC and N isotopic signatures‣ start with abundance distribution at the end of H-core burning

before envelope convection forms‣ then this signature will be mixed to the surface‣ cf. movie of abundance evolution

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ARTICLE IN PRESS




Mainstream SiC grainsC and N isotopic signatures‣ need to get C-rich‣ evolve up the AGB with 3rd DUP (REMINDER! we have already

covered all this in earlier classes!)

25 Jul 2005 8:14 AR AR251-AA43-11.tex XMLPublishSM(2004/02/24) P1: KUV

438 HERWIG

Figure 3 Thermal pulse 14, the subsequent interpulse phase and thermal pulse 15 of 2 M!,Z = 0.01 sequence ET2 of Herwig & Austin (2004). The timescale is different in each panel.The red solid line indicates the mass coordinate of the H-free core. The dotted green lineshows the boundaries of convection; each dot corresponds to one model in time. Convectionzones are light green. The shown section of the evolution comprises 12,000 time steps. Thecolors indicating convection zones, layers with H-shell ashes and the region of the 13C pocketmatch those in Figure 5.

post-AGB stars and their observational implications for the s-process (van Winckel2003). In recent years several summaries of the properties of new models have ap-peared in conference proceedings (Lattanzio & Boothroyd 1997, Blocker 1999,Herwig 2003b). A textbook on AGB stars is now available and covers the basics ofthe interior evolution and the atmosphere, circumstellar, and other observationalproperties (Habing & Olofsson 2004). This review describes the new detailedpicture of the interior evolution and nucleosynthesis that is now emerging.

According to model calculations, thermal-pulse AGB evolution is strongly massdependent. For example dredge-up efficiency, the s process, C-star formation, orhot-bottom burning are strongly correlated with specific initial mass ranges. There-fore different evolutionary properties of AGB stars can be classified according tomass, and a schematic overview is given in Figure 2. Generally stars are broadlydistinguished by their initial masses as massive, intermediate, and low-mass stars.Here low-mass stars may be designated to have M < 1.8 M! (depending on over-shoot mixing), ignite He-core burning under degenerate conditions in a flash, andend their lives as white dwarfs. Intermediate-mass stars ignite He in the nondegen-erate core and end their lives as white dwarfs, and massive stars are those massiveenough to explode as a supernova. This classification is not useful for thermal-pulse AGB stars. For example, the s-process’ nuclear production site consists of

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C and N isotopic signatures‣ again, comparison with grains‣ initial 12C/13C for AGB evolution

after first DUP too large! need for ‘extra-mixing’ !!

‣ Extra-mixing: slow (compared to convection) mixing connection between bottom of convective envelope and H-shell; physics unclear, combintation of ‣ rotation‣ magnetic fields‣ internal gravity waves‣ thermohaline mixing

f f i f f imtr f f i f f i

: c r .

: /d

i - - r:a l

' .v):

' talt !

+ij

-1

l - r l 1ft it il t ul ut l*

trr.- * -im

Wl

5; ur

HFiilUH

'Hl -[!.-'! E=r

ffiLil =

t ruq

Stardust from M eteorxtes

104

When the star ascencls tl = --rr

up carries 12C to the sr-lrfa( -

r ich and hence SiC grainS Li : - , .rzgltzg ratio reaches \:ahie: r .-

and between - 40 and 6() ir- -

ratios are unaffected br- the ,l --

As shown in Fig. 4.7. t l i , .

qualitatively explained usinc -. .

and mixing occurr ing dur t r r ' * ' :

This is part icular ly t rue i f : , , : - , '

is included in the models. . r : r -

above. Hou'ever, the range,-,- --

t lre condition that CIO > 1. -

covered by SiC grain data. l -

\-alues than those predicteci

and below the theoretical i i t...-

The extra-mixing pheire,ti- ' -

rvork not only during the t 'e' l --

r in th is case they are sut l iet i i r . ' - ,

they seem to be requireci to r : - ' -

of presolar oxide grains 2r l r

also explain SiC grain data .-..-

ratios than those covered br -- .

216). Note that there are r , , ,

r r r ix ing could occur dur i r rg r i '

u'ith the advancement of the Fi-

mass) the H-burning sheil i t-.- ,

clestroyed the discontinuitr ir,

up.

On the other hand. grait.. -

difficult to account for. sitrct . -

dicted to occur. They cor-tl, i : ' .

posi t ion of the star. In fact . . r . . - .

the life of the Galaxy. Hor'.', -.' -

isotopes is very compler atr , r - - .

the abundance of 1aN Rp])!i- r : '

component. while 15N is pr' . "

SNII . Even the solar isoto1t, , . . .

factor of two l22I].

7.|r)

zt,

i 000

1001 100

r2(- / 13c."/

v

Fig. 4.7 The C and N compositions measured in single mainstream SiC grains (squares,

from Fig. 4.1) are compared to the evolution of the isotopic ratios predicted at the stellar

surface for stellar models of 3,A,19 (circles) and 1.5 &f9 (triangles) with initiai solar

composition during the red giant and AGB phase. The solid l ines represent the change

in composition starting from solar initial values to the values produced by the operation

of the first dredge-up and extra-mixing phenomena during the red giant phase (see text

for details). The open symbols represent the change in composition during the AGB

phase because of the operation of the third dredge-up. The larger symbols are employed

when the condition for the formation of SiC, CIO > 1, is satisfied in the envelope.

2.3 Me. This is because, in this case, the red giant phase lasts long enough

to allow the H-burning shell to progress to a point in mass where it can de-

stroy the barrier to mixing due to the composition discontinuity left behind

by the first dredge-up (visible at around 0.5 Ma in Fig. 4.6). This type

of non-standard mixing could be generated by rotation and/or magnetic

fields. However, exactly what drives the extra mixing, and how it works is

still largely unknown.



22Ne/He tripple isotope plot:‣ composition resulting from the

mixing of two distinct components on straight line connecting the two components

‣ location on line indicates mixing degree

‣ N-component solar‣ G-component: intershell of AGB

stars

!}ep aq? dq u.lrroqs uor+tslaJJoc poo8 ar{J, 'rBlos o} asolc uorlrsoduroc e a^!q

o1 ua>le+ dlerrddl sr luauoduoc NI aql ',{1a.tr1cadsa.r ,syuauodu,to, ((O,, pue

,,NJ,, o{} pall!J ore ((s}uorpa;3ur,, ollr} asarlil 'dn-e8pa-rp prSi} fq adola,rua

aq? o?ul Iloqsrolul aH aql ruoq paxru itsrra1!ur oq? pu! '"re1s aq1 3o adol

-alua aq? ul luasa"rd d11er1rur lerra?!ru aq? uao.4.1oq aJn?xrur e .,{q pacnpo-id

se,lrr lurod qrea dq paluasa"rdor uorlrsodrnoc oql 1!q? 8ur.u.oqs se pala;rdralur

sl slqJ '8'f '8lC 3o 1o1d edolosr-aarr{} aq} ur aurl 1q8re"r1s ! uo er1 slurod

'polecrpur sr r!?s aq] Jo .{1rcr11e1auroql puE 's1oqur.,(s uado se uâoqs arc (luauodruoc p) sr!?s gDV Jo Ilaqsralur aH ar{} Jouorlrsodurol aql roJ suorlrrpard I!JrloroaqJ 'sluauoduroc C aql pu! N aq? Jo Furxrru

3o saer8ap snolr!,t Jo su!aur .{q parnpo"rd uaaq Sur,teq se palard.ra}ur aJe suorlrsoduroe

po Josqo aql 'srels gCV Jo llaqsJalul eH aq? ur pacnpord luauoduro) ,,C,, aq? sarl

aurl Surxrur oql Jo pua lJal ruolloq aql oJ .(fo1d aef ur al!rs 3o 1no) V.ZI:aNzz/"N0.pue vIIZ:oNzz/oHr :sorler r!los aq? oJ asolD 'luauodruoc ((N), Ieruror aq+ serl aurl

Surxrtu aql Jo pue 1q8r.r "raddn aql oJ 'sluauodruoc oml uaa.&\1aq aurl Surxrru oql sE

pa1a.rd"ra1ur sI qtlq,â 'aur1 uorlelarror e?Ep aql sluasaJda.r aurl prlos aqJ '(azrs ure"r8 aq1

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sazrs ?uaraJrp;o sure-r8 CIS ul parnseatu sorl!r oN73/aNs6 pue a51../aHr orlJ g.t .FI.{

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gov prrB (aNiz.

Surcnpo.rc : :.-,

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luauodruoc (tt)g-aX or{l ]12 ;

salelaJJo) aNzz Jo a)tlepull(rL. --. - -

cls lBq+ paroôlslp se-\\ lI ----

oNzz olur sderap qllq-\\ 'p-\:_ -:

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pa,,r.allaQ sI ?I (p!alsul 'iTl:i :'

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olSurs ur uolllsoduor .IIJU- -;t -'

'sase8 olqou ul!luoJ o] ttlaa> .- ' .

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'luauodruo) snol!tuou! (H l--..',.

]tIatI{-}dIli

,rtpnls o1 sute.r8 CIS ot tiollpII;"; -',

{",iI 'sasBLId qclJ-ua8.\xo .II-r - -

o1 paârloq oslB are (t'9 'rJ( -,--

aq? ulqll,Lr. pala-rdJoJul oQ r.ii ,.-'

ur paôrqJ! aq plnoJ {Sts} SI--;- --

JSn!Jaq sure-r8 CIS ul qottr:.t . .

uaaq ?ou s!q 1r (.,(laleunl.ro]ti_

I

-sod (os1e pu! sr!}s gCy puE ---

posn aq usJ sur!J8 ruea;lsulPTl. -

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Al isotopes:‣ 25Mg/24Mg ~ 10% solar, 26Mg/24Mg

shows large excess → presence of live 26Al

‣ → extrapolate back to time of grain condensation: 26Al/27Al ~ 10-3 for mainstream grains and ~10-2 for A+B grains

‣ 26Al nucleosynthesis: H-burning if T high enough for MgAl cycle

‣ for DUP has to go through He-flash conv. zone → high cross sections of (n,p) and (n,α) reactions destroy some of the 26Al (NP program with new detector NEURAL at TRIUMF/LANL)

their stellar sources. The X grains have 26Al/27Al of up to !0.6 (Fig. 8), whereasratios in A+B and mainstream grains typically do not exceed 0.01 (Hoppe et al.,1994; Amari et al., 2001a). Isotopic compositions were also measured for Ca and Ti(Ireland et al., 1991; Amari et al., 1992, 2001a, b; Hoppe et al., 1994, 1996, 2000;Nittler et al., 1996; Alexander and Nittler, 1999; Hoppe and Besmehn,2002; Besmehn and Hoppe, 2003) and Fe, Zr, Mo, Sr, Ba, and Ru (e.g., Nicolussiet al., 1997, 1998a, c; Pellin et al., 2000a, b; Davis et al., 2002; Savina et al., 2003a, b,2004).

5.1.3. Trace elements in individual SiC grainsSilicon carbide grains contain several trace elements, some of them in considerable

amounts. Magnesium concentrations are typically around 100 ppm and Alabundances can reach several mass-percent (e.g., Hoppe et al., 1994). Nitrogen,probably substituting for carbon in the SiC lattice, shows relatively highconcentrations so the N-isotopic ratios can be analyzed with reasonable precision.However, determination of the absolute concentration of N is difficult as carbonmust be present to produce CN" which is used to analyze N by the ion probe (Zinneret al., 1989). In addition to Al and Mg, concentrations of Ca, Ti, V, Fe, Sr, Y, Zr,Nb, Ba, Ce, and Nd were measured in 60 SiC grains (average size: 4.6 mm) and inthree size-sorted SiC aggregates of 0.49–0.81 mm (Amari et al., 1995c). The general

ARTICLE IN PRESS

12C /

13C

1 10 100 1000 10000

26A

l/27A

l

100

10-1

10-2

10-3

10-4

10-5

graphite

Si3N4

SiC - A+B

SiC-mainstr.

SiC - X

SiC - Y

SiC - nova

Fig. 8. Inferred 26Al/27Al ratios versus 12C/13C ratios in SiC and low-density graphite grains.The SiC type X and graphite grains have the largest 26Al/27Al. See text for data sources.


gierterNachdruck 1 998 21

Sc44,955910

o 27,2

Sc 40183 ms

p+ 5,7; 9,6. . .

1 3737;755.. .pp 1,09;1,00..Bc 3,31; 3,75.

Sc 41596 ms

a+tr8

i rz-sis, zgsgl

Sc 4261s | 0,68s

"y 438;1525;1227

p+ 5,4...1 (1525..

Sc 433,89 h

g* 1,2. . .t373.. .

18

17

20

19

Ca40,078

r 0,43

Ca 3550 ms

a+

pzp 4,09; 3,29r 810-

Ca 36102 ms

R+

9p 2,550.. .r1619;1113;1184',

Ca37181 ms

p+9p 3,10;0,87;3,17...'y 3239; 2750;1 970..-.

Ca 38439 ms

p c,o. . .1 1568-. .m

Ca 39860 ms

tQ522\

Ca 411,03 . 105 a

noa

,K39,0983

K35190 ms

A+

r2983;2590.. .gp 1,425;'I ,705; 1 ,555...

K36342 ms

g+ 9,9 .."t 1970;2433:2208...Pp 0,970;0,693...Ba 2,015;2,725...

K371,22 s

B+ 5,1. . .t2796...

K38924,6 ms | 7,6 m

p* 5,0 1 2168..

1 ,28 . 10e ap- 1,3; e; P+.. .1 1461; on.o 4,4o30; on. q 0,39

Ar39,948

0,66

Ar 3115,1 ms

a+pp 2,08; 1,43.. .gzp 7,16p3p 4,40

Ar 3298 ms

g* 9,0. . .

Bp 3,35; 2,42.. .

1 461; 707 . ..

Ar 33174,1 ms

p+ 9,8; 10,6. . .

r810;1542;223' l ' . . .Bp 3,17.. .

Ar 34844 ms

B+ 5,0. . .^v666;3129.. .s

Ar 351,78 s

p+ 4,9. . ."y1219; (1763..

Ar 3735,0 d

no1

o6. p 69

on. a 1 970

Ar 39269 a

p- 0,6no "yo 600

c l35,4527

r 33,6

c l 31150 ms

A+

Bp 0,99; 1 ,52. .

c l32291 ms

F+ 9,5i 11,7. . .

12231;4770...

fu 2,20;1,67...pp 0,991 i 0,762; 1 ,324. . .

cl 332,51 s

p+ 4,5. . .'y(841;1966;2867...)

ct 3432,0m I 1,53sp.2,5... I12127. I

lll3 1*,,ul"r 146 | n0 1

ct 363,0 . 105 a

B- 0,7e; B+.. .no "Yo<10

cl 3837,18 m

p- 4,9. . .

t2168:1642.. .

ct 3956m

P- 1,9; 3,4. . .

t 1267;25Q:1517.. .

168

1 5 l",t,.tttt '

s2721 ms

A+

ppB2p 5,94

s28125 ms

pp 2,98; 1,46;3,70.. .

s29187 ms

g+1 1384.. .pp 5,4412,'t3..

s301,18 s

p* 4,4

1 678.5,1 . . .

s312,58 s

g+ 4,4. . .1 1266.. .

s3587,5 d

g- o,2no'y

s375,0 m

p- 1 ,8; 4,9. . .

1 31 03.. .

s382,83 h

B- 1 ,0; 2,9. . .

t 1942; '1746

P2620 ms

g+pzp 4,929p 7,271 6,84

P27260 ms

Rf

9p 0,73; 0,61..

P28268 ms

p+ 11,5. . .

t 1779; 4497...pp 0,680; 0,956Bo 2,105; 1,434

P294,1 s

p* 3,9. . .

1 1273...

P302,50 m

F* 3,2. . .1(2235.. .1

P3214,26 d

|d.1,7

nol

P3325,34 d

B- 0,2nof

P3412,4 s

p- 5,4. . .y 2127.. .

P3547,4 s

p- 2,3..."y 1572...

P365,6 s

r 3291; 903;1638;2540.. .

P372,31 s

R_

r646;1583;2254...

B1

iIi

I

I

IIIl

I

si 2342,3 ms

Rf

gp 2,4Oi 2,83...

92p 5,86; 6,18

si 24140 ms

g+

8p 1,51;4,09..

si 25218 ms

af

pp 4,09; 0,39;

1 1369-. . .

si 262,21 s

p+ 3,8. . .

t829;'1622...m

si 274,16 s

g+ 3,8. . .t QZlO.. . \

s i 312,62 h

p- 1,5. ."y (1266)o 0,3

si 32172 a

g- 0,2no1

si 336,18 s

B- 3,9; 5,8. . .

1 1848.. .

si 342,77 s

p- 3,1t 1179:429;1 608

si 3s0,78 s

R_

r 4101 ; 2386;3860; 241.. .

si 360,45 s

r 1 75; 250:878:425...

Al 2259 ms

B+pp'1,32i 0,72...gzp 4,48...po 3,27

Al 23470 ms

R+

pp 0,83

Al 24129 ms

I 2,07 s

\426 | Pt4,4;8,7B+13.3. . 111369;11369. 12754,8n142 17069.. .1,79 I Bo 1,98...

Al 257,18 s

p+ 3,3. . .'y (1612.. . )

At 266,35 s | 216.

I 10sa

I B' 1,2I 1 18oe;

B* 3,2 | 1130.. .

AI 282,246 m

Al 296,6 m

p- 2,5. . .

t 1273;2426;2028..,

At 303,60 s

p- 5,1; 6,3. . .

t2235;1263;3498.. .

Al 31644 ms

9- 5,6; 7,9. . .'v 2317; 1695

Al 3233 ms

t 1941:3042;4230...

Al 3354 ms

Al 3460 ms

B_r 3328; 930;125;4257Bn

Ar 35- 150 ms

Bn

Mg 21122,5 ms

o+

r 332; 1 384;1 634-. . .Bp 1,94i ' l ,77. . .

Mg 223,86 s

B+ 3,2. . .

r583;74.. .

Mg 2311,3 s

g+ 3,1 . . .

1 440.. .

Mg 279,46 m

B- 1 ,8. . .t844:1Q14.. .o 0,07

Mg 2820,9 h

g- 0,5; 0,9.- .

t 31; 1342:401' ,942.. .

Mg 291,30 s

9- 4,3;7,5. . .

t2224;1398;960.. .

Mg 30335 ms

B- 6,1 . . .t?44;444.. .

Mg 31230 ms

B_1 1 61 3; 947;'1626; 666...pn

Mg 32120 ms

R-

t 2765;736;2467Bn

Mg 3390 ms

p-Bn

Mg 3420 ms

pn

Na 20446 ms

p+ 11,2. . .pa 2,15;4,44..

1 1634.. .

Na 2122,48 s

p+ 2,5...y 351 . . .

Na 222,603 a

B+ 0,5; 1,8

1'1275o6,p 28000on,s 260

Na 2420 ms | 14,96 h

I B- t'+'ty472 1j2754;B -6 1136e.. .

Na 2559,6 s

B- 3,8. . .

r 975; 390;585;1612.. .

Na 261,07 s

p- 7,4. . .

1 1809.. .

Na 27304 ms

B- 8,0. . .

r985;1698..Bn 0,46.. .

Na 2830,5 ms

B- 13,9. . .

1 1474;2389.. .

Bn

Na 2944,9 ms

p- 10,8; 13,4.

r 55; 2560;1474-. . .Bn 4,13; 1,70.

Na 3048 ms

g- 12,2i 15,7.

t 1482: 1Q40-;1 978.. .pn; g2n; pa

Na 3117,0 ms

B- 15,4. . .

1 51;1482':2244pn 0,08;0,51.. .

P2n

Na 3213,5 ms

B_r886;2153.. .Bn; B2n

Na 338,2 ms

R_

Pn; P2nr 886-; 547;1243...

Ne 1917,22 s

g+ 2,2. . .

1(110;197;1 357)

Ne 2337,2 s

9 4,4. . .^v440;1639.

Ne 243,38 m

g- 2,o. . .'y874m

Ne 25602 ms

Ii- 7,3. . .'y90:980.. .

Ne 26197 ms

B_183;233.. .BN

Ne 2732 ms

pn

Ne 2817 ms

R-

Bn

Ne 29- 200 ms

p-9n

Ne 30 t\e Jz

F18109,7 m

p+ 0,6no1

F2011,0 s

p- 5,4. . .v 1634.. .

F214,16 s

B- 5,3; 5,7. . .^,aRi.1eoE

F224,23 s

F- 5,5. . .

t 1275: 2Q83;2 1 66.. .

F232,23 s

F240,34 s

R_

ry1982

F2559 ms

R-

Bn

F26 F27 F29

22

22

21

o1927,1 s

p- 3,3; 4,7. . .

t 197; 1357..

o2013,5 s

p- 2,8. . .ry 1057.. .

o213,4 s

g- 6,4. . .

r 1 730; 351 7280i 1787...

o222,25 s

t72:637;1 862.. .

Q2382 ms

p-Bn

o2461 ms

' t8 20

N 167,13 s

p- 4,3;10,4. . .

I 6129;71 15.. .

Ba 1,76.

5,3 ps

l1 120

l t . .

N174,17 s

9- 3,21 8,7. . .

Bn 1 l7; 0,38."t 871;2184ipo 1,25; 1,41

N180,63 s

9- 9,4; 11,9...

j 1982: 822: 16521 2473p0 1,08;1,41.. .

0n 1 35; 2,46...

N19329 ms

p-pn"y96;3138;709

N20142 ms

p-Fn

N2195 ms

Bn

N2224 ms

p-pn

N23

c152,45 s

p- 4,5; 9,8. .^,

(2AR

c16o,747 s

9- 4,7i7,9. . .

9n O,79i 1,72

c17193 ms

Bn 1,62.- ..i 1375t 1849;1 906.. .

c1892 ms

R_

r2614;880;2499...

Fn C;88; 1,55.. .

c1949 ms

Fn 1,01;0,46.. .g2n

c2014 ms

Bn

c22

81413,8 ms

p,- 14,0. . .

r 6090; 6730gn

81510,4 ms

B_gn 1,77,.3,20...

8175,1 ms

p-Bn; B2n;B3n; p4n

B 19

16

Be 144,35 ms

9-pn <0,8; 3,02:3,52.. .; g2n

1 3528';3680'

12 14

10


Si triple isotope plot:‣ mainstream grains show a correlation line (the ‘mainstream

line’) that does not pass through the solar value‣ the mainstream line has a slope of 1.3, but intrinsic

nucleosynthesis in AGB stars predict a slope of only ~0.5, implying a larger 30Si than 29Si production

Fig. 12. Probability distribution of mainstream SiC Si-isotopic compositions generated by summing Gaussian distributions corresponding to measurement uncertainties for individual grains. (a) Contour plot of probability distribution. The solid line is the best-fit line to the mainstream grains (Fig. 11). (b) Shaded surface representation of distribution. The location of grain groups IV, V, and VI, defined by [Huss et al., 1997] are indicated; groups V and VI were not seen in the present study ( Fig. 11) and group IV has a much a lower abundance in Murchison than in Orgueil data of [Huss et al., 1997]. (Nittler & Alexander, 2003)

The SiC grains of type X, !1% of all SiC, have higher 12C/13C and lower 14N/15Nthan the respective solar ratios. The X grains have low d29Si and d30Si values, and28Si excesses reach up to 5" solar (Amari et al., 1992; Hoppe et al., 2000; Amari andZinner, 1997). Another 1% of all SiC grains have 12C/13C4100 and 14N/15N abovethe solar ratio (Amari et al., 2001b; Hoppe et al., 1994). These Y grains appear to be12C-rich mainstream grains but their 30Si/28Si ratios are slightly larger than inmainstream grains, which merits placing them into a separate group. Up to 3% of allSiC grains, particularly among smaller-sized grain fractions, are Z grains. Their12C/13C and 14N/15N ratios are similar to those of mainstream grains, but Z grainshave large 30Si excesses (Alexander, 1993; Hoppe et al., 1997). Only a few nova SiCgrains, with 12C/13C ¼ 4–9, and 14N/15N ¼ 5–20, are known (Amari et al., 2001c;Jose et al., 2004; Nittler and Hoppe, 2004a, b). Most nova grains have close-to-solar29Si/28Si but 30Si excesses.

Many SiC grains have 26Mg/24Mg larger than the solar ratio but solar 25Mg/24Mgwithin 10% (Amari et al., 1992, 2001a–c; Hoppe et al., 1994, 2000; Huss et al., 1997).Magnesium in some X grains is almost pure 26Mg, and 26Mg excesses are most likelyfrom in situ decay of 26Al (t1/2 ¼ 7.3" 105 a) that was incorporated into grains at

ARTICLE IN PRESS

!30Si

!2

9S

i

-800 -600 -400 -200 0 200 400 600 800-800

-600

-400

-200

0

200

400

600

SiCmainstream ~93%

A+B 4-5%

X ~ 1%

Y ~1%

Z ~1%

nova

Si3N

4

Fig. 7. The Si-isotopes for presolar SiC grains (references as in Fig. 6) and stars (symbols witherror bars) are given in the d-notation which describes the deviation of an isotope ratio (iN/jN)of a sample from the (terrestrial) standard ratio in per-mil: diN(%) ¼ [(iN/jN)sample/(iN/jN)standard–1]" 1000. The grains fall into distinct populations. The triangles show twodeterminations for the C-star IRC+101216 (Cernicharo et al., 1986, Kahane et al., 1988). Theother stellar data (circles) are for O-rich M-giants (Tsuji et al., 1994).

K. Lodders, S. Amari / Chemie der Erde 65 (2005) 93–166 111

δ(mX/nX) =(

(mX/nX)measured/modeled

(mX/nX)!− 1

)× 1000

28Si(n, γ)29Si(n, γ)30Si and 32S(n, γ)33S(n, α)30Si


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Sc 40183 ms

p+ 5,7; 9,6. . .

1 3737;755.. .pp 1,09;1,00..Bc 3,31; 3,75.

Sc 41596 ms

a+tr8

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"y 438;1525;1227

p+ 5,4...1 (1525..

Sc 433,89 h

g* 1,2. . .t373.. .

18

17

20

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r 0,43

Ca 3550 ms

a+

pzp 4,09; 3,29r 810-

Ca 36102 ms

R+

9p 2,550.. .r1619;1113;1184',

Ca37181 ms

p+9p 3,10;0,87;3,17...'y 3239; 2750;1 970..-.

Ca 38439 ms

p c,o. . .1 1568-. .m

Ca 39860 ms

tQ522\

Ca 411,03 . 105 a

noa

,K39,0983

K35190 ms

A+

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K36342 ms

g+ 9,9 .."t 1970;2433:2208...Pp 0,970;0,693...Ba 2,015;2,725...

K371,22 s

B+ 5,1. . .t2796...

K38924,6 ms | 7,6 m

p* 5,0 1 2168..

1 ,28 . 10e ap- 1,3; e; P+.. .1 1461; on.o 4,4o30; on. q 0,39

Ar39,948

0,66

Ar 3115,1 ms

a+pp 2,08; 1,43.. .gzp 7,16p3p 4,40

Ar 3298 ms

g* 9,0. . .

Bp 3,35; 2,42.. .

1 461; 707 . ..

Ar 33174,1 ms

p+ 9,8; 10,6. . .

r810;1542;223' l ' . . .Bp 3,17.. .

Ar 34844 ms

B+ 5,0. . .^v666;3129.. .s

Ar 351,78 s

p+ 4,9. . ."y1219; (1763..

Ar 3735,0 d

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Ar 39269 a

p- 0,6no "yo 600

c l35,4527

r 33,6

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c l32291 ms

F+ 9,5i 11,7. . .

12231;4770...

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cl 332,51 s

p+ 4,5. . .'y(841;1966;2867...)

ct 3432,0m I 1,53sp.2,5... I12127. I

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B- 0,7e; B+.. .no "Yo<10

cl 3837,18 m

p- 4,9. . .

t2168:1642.. .

ct 3956m

P- 1,9; 3,4. . .

t 1267;25Q:1517.. .

168

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pp 2,98; 1,46;3,70.. .

s29187 ms

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s312,58 s

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s3587,5 d

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p- 1 ,8; 4,9. . .

1 31 03.. .

s382,83 h

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t 1942; '1746

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g+pzp 4,929p 7,271 6,84

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Rf

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P28268 ms

p+ 11,5. . .

t 1779; 4497...pp 0,680; 0,956Bo 2,105; 1,434

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p* 3,9. . .

1 1273...

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p- 5,4. . .y 2127.. .

P3547,4 s

p- 2,3..."y 1572...

P365,6 s

r 3291; 903;1638;2540.. .

P372,31 s

R_

r646;1583;2254...

B1

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Rf

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92p 5,86; 6,18

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g+

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af

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p+ 3,8. . .

t829;'1622...m

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g+ 3,8. . .t QZlO.. . \

s i 312,62 h

p- 1,5. ."y (1266)o 0,3

si 32172 a

g- 0,2no1

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B- 3,9; 5,8. . .

1 1848.. .

si 342,77 s

p- 3,1t 1179:429;1 608

si 3s0,78 s

R_

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\426 | Pt4,4;8,7B+13.3. . 111369;11369. 12754,8n142 17069.. .1,79 I Bo 1,98...

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p+ 3,3. . .'y (1612.. . )

At 266,35 s | 216.

I 10sa

I B' 1,2I 1 18oe;

B* 3,2 | 1130.. .

AI 282,246 m

Al 296,6 m

p- 2,5. . .

t 1273;2426;2028..,

At 303,60 s

p- 5,1; 6,3. . .

t2235;1263;3498.. .

Al 31644 ms

9- 5,6; 7,9. . .'v 2317; 1695

Al 3233 ms

t 1941:3042;4230...

Al 3354 ms

Al 3460 ms

B_r 3328; 930;125;4257Bn

Ar 35- 150 ms

Bn

Mg 21122,5 ms

o+

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Mg 223,86 s

B+ 3,2. . .

r583;74.. .

Mg 2311,3 s

g+ 3,1 . . .

1 440.. .

Mg 279,46 m

B- 1 ,8. . .t844:1Q14.. .o 0,07

Mg 2820,9 h

g- 0,5; 0,9.- .

t 31; 1342:401' ,942.. .

Mg 291,30 s

9- 4,3;7,5. . .

t2224;1398;960.. .

Mg 30335 ms

B- 6,1 . . .t?44;444.. .

Mg 31230 ms

B_1 1 61 3; 947;'1626; 666...pn

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R-

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p-Bn

Mg 3420 ms

pn

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p+ 11,2. . .pa 2,15;4,44..

1 1634.. .

Na 2122,48 s

p+ 2,5...y 351 . . .

Na 222,603 a

B+ 0,5; 1,8

1'1275o6,p 28000on,s 260

Na 2420 ms | 14,96 h

I B- t'+'ty472 1j2754;B -6 1136e.. .

Na 2559,6 s

B- 3,8. . .

r 975; 390;585;1612.. .

Na 261,07 s

p- 7,4. . .

1 1809.. .

Na 27304 ms

B- 8,0. . .

r985;1698..Bn 0,46.. .

Na 2830,5 ms

B- 13,9. . .

1 1474;2389.. .

Bn

Na 2944,9 ms

p- 10,8; 13,4.

r 55; 2560;1474-. . .Bn 4,13; 1,70.

Na 3048 ms

g- 12,2i 15,7.

t 1482: 1Q40-;1 978.. .pn; g2n; pa

Na 3117,0 ms

B- 15,4. . .

1 51;1482':2244pn 0,08;0,51.. .

P2n

Na 3213,5 ms

B_r886;2153.. .Bn; B2n

Na 338,2 ms

R_

Pn; P2nr 886-; 547;1243...

Ne 1917,22 s

g+ 2,2. . .

1(110;197;1 357)

Ne 2337,2 s

9 4,4. . .^v440;1639.

Ne 243,38 m

g- 2,o. . .'y874m

Ne 25602 ms

Ii- 7,3. . .'y90:980.. .

Ne 26197 ms

B_183;233.. .BN

Ne 2732 ms

pn

Ne 2817 ms

R-

Bn

Ne 29- 200 ms

p-9n

Ne 30 t\e Jz

F18109,7 m

p+ 0,6no1

F2011,0 s

p- 5,4. . .v 1634.. .

F214,16 s

B- 5,3; 5,7. . .^,aRi.1eoE

F224,23 s

F- 5,5. . .

t 1275: 2Q83;2 1 66.. .

F232,23 s

F240,34 s

R_

ry1982

F2559 ms

R-

Bn

F26 F27 F29

22

22

21

o1927,1 s

p- 3,3; 4,7. . .

t 197; 1357..

o2013,5 s

p- 2,8. . .ry 1057.. .

o213,4 s

g- 6,4. . .

r 1 730; 351 7280i 1787...

o222,25 s

t72:637;1 862.. .

Q2382 ms

p-Bn

o2461 ms

' t8 20

N 167,13 s

p- 4,3;10,4. . .

I 6129;71 15.. .

Ba 1,76.

5,3 ps

l1 120

l t . .

N174,17 s

9- 3,21 8,7. . .

Bn 1 l7; 0,38."t 871;2184ipo 1,25; 1,41

N180,63 s

9- 9,4; 11,9...

j 1982: 822: 16521 2473p0 1,08;1,41.. .

0n 1 35; 2,46...

N19329 ms

p-pn"y96;3138;709

N20142 ms

p-Fn

N2195 ms

Bn

N2224 ms

p-pn

N23

c152,45 s

p- 4,5; 9,8. .^,

(2AR

c16o,747 s

9- 4,7i7,9. . .

9n O,79i 1,72

c17193 ms

Bn 1,62.- ..i 1375t 1849;1 906.. .

c1892 ms

R_

r2614;880;2499...

Fn C;88; 1,55.. .

c1949 ms

Fn 1,01;0,46.. .g2n

c2014 ms

Bn

c22

81413,8 ms

p,- 14,0. . .

r 6090; 6730gn

81510,4 ms

B_gn 1,77,.3,20...

8175,1 ms

p-Bn; B2n;B3n; p4n

B 19

16

Be 144,35 ms

9-pn <0,8; 3,02:3,52.. .; g2n

1 3528';3680'

12 14

10


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Pre-solar Grains - University of Victoria