Trace Element Abundances in Single Presolar SiC Stardust Grains by Synchrotron X-Ray Fluorescence...
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Transcript of 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
Fe Ni S Cr Co Mn Ca Ti V Sr Y Zr Nb Mo Ru Os Ir Pt
Enr
ichm
ent f
acto
r
Element
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
b
Fe Ni S Cr Co Mn Ca Ti V Sr Y Zr Nb Mo Ru Os Ir Pt
Enr
ichm
ent f
acto
r
Element
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
g
Fe Ni S Cr Co Mn Ca Ti V Sr Y Zr Nb Mo Ru Os Ir Pt
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)
Example of two correlated trace elements (2):
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)
Example of two correlated trace elements (3):
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)
Ti (Si and CI normalized)
22.5-21
24.5-36b
22.5-12
22.5-10
22.5-3
18-18Na
Example of two correlated trace elements (4):
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)
Ti (Si and CI normalized)
Example of two correlated trace elements (5):
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
Example of two correlated trace elements (6):
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