trace element abundances in single presolar sic stardust grains by synchrotron x-ray fluorescence...

Trace Element Abundances in

Single Presolar SiC Stardust Grains

by Synchrotron X-Ray Fluorescence

(SXRF)Zhonghu Cai (XOR)

Barry Lai (XOR)

Steve Sutton (CARS)

Bob Clayton

Andy Davis

Roy Lewis

Yoav Kashiv

The never ending story…

Zhonghu Cai (XOR)

Barry Lai (XOR)

Steve Sutton (CARS)

Bob Clayton

Andy Davis

Roy Lewis

Yoav Kashiv

Types of presolar stardust grains found

(an incomplete list)

Carbides

• Diamond (C)

• SiC

• Graphite (C)

• TiC (subgrains)

• Fe-Zr-Mo-Ru carbides

(subgrains)

Oxides

• Corundum (Al2O3)

• Spinel (MgAl2O4)

• Hibonite (CaAl12O19)

• TiO2

• Mg-Fe Silicate

[(Mg,Fe)SiO2, olivine?]

Other

• Si3N4

Summary of properties of some grains(Zinner, 1998; Bernatowicz et al., 1996)

Grain Group Group

fraction

Abundance Crystal size Stellar sources

(%) (ppm wt.)

Diamond ~500 ~2 nm SN

SiC ~10 ~0.3- 20 mm

Mainstream ~90 C- rich TP- AGB

A ~2 C- rich TP- AGB

B ~2 C- rich TP- AGB

X ~1 SN

Y ~1 C- rich TP- AGB

Z ~1 C- rich TP- AGB

Nova < 1 Nova

Graphite ~2 ~1- 20 mmSN, C- rich TP-

AGB, Nova

Ti- , Zr- , Mo- ,

Ru- carbide

Subgrains in

graphite~3- 220 nm

Same as the host

graphite

Corundum (Al2O3) ~0.04 ~0.5- 3 mm RG, TP- AGB

Si3N4 ~0.002 ~1 mm SN

How do we identify and classify stardust grains?

By their isotopic composition which is very different

from ‘average’ solar system composition.(Plot by A. Davis, compilation of data from several sources)

SiC group 12C/ 13C 14N/ 15N

Mainstream 15 - 100 > 272

A < 3.5

B 3.5 - 15

X < 272

Y > 100 > 272

Z < 100

And classified by their Si isotopic composition as

well.(Plot by A. Davis, compilation of data from several sources)

SiC group 29Si 30Si Slope

Mainstream most > 0 most > 0 1.34

A most > 0 most > 0 1.34

B most > 0 most > 0 1.34

X < 0 < 0 < 1

Y > 0 > 0, > 29Si

Z > 0, > 29Si

A Fe-rich sub-grain (metallic Fe or Fe-carbide)

inside

A presolar graphite grain.(Bernatowicz et al., 1996)

What affects the abundance of a trace element in

the grains?

1. The composition of the stellar atmosphere gas:

• The initial composition of the star.

• Nuclear burning in the star (if applies).

• Mixing in the star (dredge-up events).

2. The time dependent physical conditions in the stellar atmosphere:

p-Tcurves.

3. The thermochemical behavior of the element under the chemical

and physical conditions: refractory, volatile, etc.

4. The trace element incorporation mechanism:

condensation as an inclusion, condensation in solid solution, other?

The experiment was conducted at

the Advanced Photon Source (APS)

at Argonne National Lab (ANL).

The experimental technique that was used is

Synchrotron X-Ray Fluorescence (SXRF).

Unlike in astronomical spectroscopy here we are

looking at electronic transitions between inner

shells.

Unlike starlight the x-ray beam energy is tunable.

This is done with an insertion device (ID) called an

undulator.

A residual grain spectrum (i.e., with background

subtracted) taken with a primary x-ray beam energy of

22.5 keV.

0

10

20

30

40

50

60

70

80

0 5 10 15 20

Grain #14

Num

ber

of Counts

X-ray Energy (keV)

Si

Y

Zr

Ti

Mn

FeV

Ni

W

Mo

Ru(S)

Nb

Sr

Minor and trace elements detected

in presolar SiC grains

(an incomplete list)

In aggregates

Ne, Ar, Kr, Xe,

Sm, Dy.

In single grains

1. Abundance:

N, Mg, Al, Ca, Ti,

V, Fe, Sr, Y, Zr,

Nb, Ba, Ce, Nd.

2. Isotopic composition:

B, N, Mg (Al),

Ti (V), Fe, Sr, Zr,

Mo, Ru (Tc), Ba.

This study

1. Detected before:

Ca, Ti, V, Fe,

Sr, Y, Zr, Nb.

2. New elements:

S, Cr, Mn, Co,

Ni, Mo, Ru, W,

Os, Ir, Pt.

The general grain pattern.

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

Fe Ni S Co Cr Mn Ca Ti V Sr Y Zr Nb Mo Ru Nd W Os Ir Pt

Enr

ichm

ent

fact

or

Element

(22.5 keV)

Examples of specific grain patterns.

10-5

10-4

10-3

10-2

10-1

100

101

102

Fe Ni S Cr Co Mn Ca Ti V Sr Y Zr Nb Mo Ru Os Ir Pt

a


Enr

ichm

ent f

acto

r

Element

10-5

10-4

10-3

10-2

10-1

100

101

102


b


Enr

ichm

ent f

acto

r

Element

10-5

10-4

10-3

10-2

10-1

100

101

102


g


Enr

ichm

ent f

acto

r

Element

Comparison of the general grain pattern

with calculations of a 1.5 Msolar AGB star.

(Gallino et al., private communication)

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

Fe Ni S Co Cr Mn Ca Ti V Sr Y Zr Nb Mo Ru Nd W Os Ir Pt

En

richm

ent

fac

tor

Element

(22.5 keV)

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

0 Fe Ni S Cr Co Mn Ca Ti V Sr Y Zr Nb Mo Ru W Os Ir Pt 20

M1.5, st

CI

M1.5, st, p9, no decay

M1.5, st, p9, + decay

M1.5, st, p17, no decay

M1.5, st, p17, + decay

0 Fe Ni S Cr Co Mn Ca Ti V Sr Y Zr Nb Mo Ru W Os Ir Pt 20

En

richm

ent

fa

cto

r

Element

Comparison of the general grain pattern with ISM

depletions.

(Welty et al., 1999)

-5

-4

-3

-2

-1

0

1

S Mn Co Cr Fe Ni Ca Ti

De

ple

tion

(de

x)

Element

Depletions in the grains (22.5 keV)

-5

-4

-3

-2

-1

0

1

S Mn Co Cr Fe Ni Ca Ti

Cold cloud

Warm cloud

CI

De

ple

tion

(de

x)

Element

ISM depletions

Schematic correlations between two trace elements

in the grains: nuclear and chemical effects.

10-4

10-3

10-2

10-1

100

101

102

103

10-4 10-3 10-2 10-1 100 101 102 103

B=A

Bx1

Bx5

Bx10

Bx15

Bx20

Bx30

Bx40

B/2

B/5

B/10

B/50

B (

Si a

nd C

I nor

ma

lize

d)

A (Si and CI normalized)

B enrichment: nuclear and/or chemical

B chemicaldepletion

A & Benrichment:nuclear and/orchemical

A & Bchemicaldepletion

Example of two correlated trace elements (1):

no nuclear enrichment, but with chemical enrichment

(both) -

V vs. Ti.

10-5

10-4

10-3

10-2

10-1

100

101

10-4 10-3 10-2 10-1 100 101 102

V = TiThis workMainstreamABYKJAKJBKJCKJDKJEKJFM1.5Upper limit (V)

V (

Si a

nd C

I nor

ma

lize

d)

Ti (Si and CI normalized)


no nuclear enrichment and chemical depletion (both) -

Ni vs. Fe.

10-5

10-4

10-3

10-2

10-1

100

101

10-5 10-4 10-3 10-2 10-1 100 101

Ni = Fe

This work

M1.5

Ni (

Si a

nd C

I nor

ma

lize

d)

Fe (Si and CI normalized)


nuclear (Zr) and chemical enrichments (both) -

Zr vs. Ti.

10-2

10-1

100

101

102

10-2 10-1 100 101 102

Zr = TiThis workMainstreamABYKJAKJBKJCKJDKJEM1.5Upper limit (Zr)

Zr

(Si a

nd C

I nor

ma

lize

d)


22.5-21

24.5-36b

22.5-12

22.5-10

22.5-3

18-18Na


nuclear enrichment (Sr), and chemical depletion (Sr) -

Sr vs. Ti.

10-3

10-2

10-1

100

101

102

10-4 10-3 10-2 10-1 100 101 102

Sr = TiThis workMainstreamABYKJAKJBKJCKJDKJEKJFM1.5

Sr

(Si a

nd C

I nor

ma

lize

d)



nuclear and chemical enrichments (both) -

Mo vs. Zr.

10-2

10-1

100

101

102

103

10-2 10-1 100 101 102 103

Mo = ZrThis workM1.5Upper limit (Mo)

Mo

(Si a

nd C

I nor

ma

lize

d)

Zr (Si and CI normalized)

22.5-1224.5-17

24.5-30

22.5-7

22.5-2

22.5-3

24.5-36b

22.5-4

24.5-21a


nuclear and chemical enrichments (both) –

Nb vs. Zr.

10-2

10-1

100

101

102

103

10-2 10-1 100 101 102 103

Nb = ZrThis workMainstreamABKJAKJBKJCKJDKJEKJFM1.5M1.5 + decayUpper limit (Nb)

Nb

(Si a

nd C

I nor

ma

lize

d)

Zr (Si and CI normalized)

22.5-7

24.5-17

24.5-36b

24.5-30

22.5-3

22.5-2

22.5-12

24.4-21a

22.5-4

trace element abundances in single presolar sic stardust grains by synchrotron x-ray fluorescence...

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