QuickTime and a decompressor are needed to see this picture. QuickTime and a decompressor are needed to see this picture. QuickTime and a decompressor are needed to see this picture. Constraints on SN models from the isotopic compositions of presolar dust grains Ernst Zinner Washington University St. Louis Russbach Workshop 2012
In the last 25 years a new source of information on isotopic abundances in stars has become available in the form of stardust preserved in primitive meteorites. Grains from Red Giants or supernovae were included into the molecular cloud that collapsed into our Solar System. Cartoon by Larry Nittler Cartoon by Larry Nittler Some of these grains are preserved in primitive meteorites, from which they can be extracted and studied in detail in the laboratory.
Corundum Silicon Carbide Graphite Grains Diamond 500nm Silicate Grain Spinel How do we know these grains have a stella origin?
Three types of grains have isotopic compositions that indicate a SN origin SiC X grains constitute only 1% of all presolar SiC grains, SiC C grains only 0.1%. Low-density graphite grains constitute ~50% of all presolar graphite grains. Oxygen-rich SN grains are small and rare and have not been studied very much.
SiC Grains
J stars novae AGB SNe SiC X and C grains are distinct in their C and N isotopic ratios. ~500 SiC X grains but only a handful of C grains have been identified by isotopic searches.
X grains have deficits in 29 Si and 30 Si (or excesses in 28 Si) while C grains have excesses in 28 Si and 30 Si.
SNII AGB A SN origin is indicated by the large 28 Si excesses in X grains.
SiC X and C grains have larger inferred 26 Al/ 27 Al ratios than other grain types.
12 C/ 13 C = 190 14 N/ 15 N = 28 29 Si/ 28 Si = 282 30 Si/ 28 Si = 442 26 Al/ 27 Al = 0.6-0.9 Absolute proof for a SN origin comes from evidence for the initial presence of 44 Ti (T 1/2 = 60 yrs) in the form of 44 Ca excesses. 44 Ti is only produced in SNe.
Graphite Grains
Most low-density grains have 28 Si excesses like SiC X grains, but some have 29,30 Si excesses like C grains.
LD graphite grains have 15 N excesses.
LD graphite grains have 18 O excesses.
They have large 26 Al/ 27 Al ratios.
Ion Signal 44 Ti/ 48 Ti = 4.8x10-4 Some LD grains give evidence for initial 44 Ti.
Oxide Grains
Only few oxide grains have a clear SN signature. Some group 4 grains probably have a SN origin. What is puzzling is that there are not more O-rich grains from SNe.
Isotopic signatures of SN grains.
Isotopic ratios in 15M SN model.
Mixing of different zones is necessary to reproduce the grain data.
Mixing is necessary.
Ratio or Mass Fraction 1E+03 C-N O/C He/C He/N H 1E+02 1E+01 1E+00 1E-01 1E-02 1E-03 1E-04 1E-05 1E-06 12/13/sol 14/15/sol 26Al/27Al C/O 1E-07 7 8 9 Interior Mass (M ) Try to reproduce the C and N isotopic ratios of X grains by mixing between the H/C and He/N zones.
25 M SN model by Heger before and after explosive nucleosynthesis.
Can cover the N and C ratios of most X grains but need the 15 N spike. The 15 and 20 M SN models by Limongi and Chieffi don t have 15 N excesses anywhere in the star.
In the 15 M SN model 15 N is higher in the He/C zone than in the 25 M SN model.
Can cover most X grains.
In the O-rich zones the 15 N/ 14 N ratio is higher than in the He/C zone. Mix with layer at 2.4 M.
Miss most grains. In addition, O/C ~ 100.
Isotopic ratios in 15M SN model. C-Al
SN models cannot explain the high 26 Al/ 27 Al ratios observed in SiC X grains.
600 400 200 X grains 15 M SN 20 M SN 25 M SN Si 29Si/ 28 Si ( ) 0-200 -400-600 -800-1000 -1000-800 -600-400 -200 0 200 400 600 30Si/ 28 Si ( )
Ratio or Mass Fraction 1E+02 O/C He/C He/N H 1E+01 1E+00 1E-01 1E-02 12/13/sol 14/15/sol 26Al/27Al 29/28/sol 30/28/sol C/O 1E-03 7 8 9 Interior Mass (M ) A He/N-He/C mix has 29 Si and 30 Si excesses.
600 400 200 O/Ne-Si/S mix 15 M SN 2 29 Si O/Ne-Si/S mix 15 M SN 29Si/ 28 Si ( ) 0-200 -400-600 -800 X grains 15 M SN -1000-1000 -800-600 -400-200 0 200 400 600 30Si/ 28 Si ( ) Hoppe et al. proposed a contribution from the O/Ne zone to explain the composition of a grain with an 29 Si excess and 30 Si deficit.
Abundance Ratio SN-15-Rauscher 1E+1 Ni Si/S O/Si O/Ne 1E+0 1E-1 1E-2 1E-3 29Si/28Si/sol 30Si/28Si/sol 1E-4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 Mass 1E+0 Ni Si/S SN-15-Rauscher O/Si O/Ne The O/Si zone is rich in 30 Si and has much more Si than the O/Ne zone. 1E-1 1E-2 1E-3 1E-4 1E-5 ne20 si28 fe56 1E-6 1.6 1.8 2.0 2.2 2.4 2.6 2.8 Mass c12 o16
Fe SiC X grains do not show 54 Fe excesses although the Si/S zone is rich in 54 Fe and large excesses are expected.
46 Ti/ 48 Ti ( ) 2500 2000 1500 1000 500 0-500 Ti 2.6M 2.5M 2.4M 2.3M 2.05M 2.15M 2.2M -1000 1E-3 1E-2 1E-1 1E+0 44 Ti/ 48 Ti The situation is similar for 46 Ti. The lack of large 46 Ti excesses implies that only the inner Si/S zone contributes material to X grains.
C grains SiC C grains are rare. Their C, N, 26 Al/ 27 Al and 44 Ti/ 48 Ti ratios indicate a SN origin.
Si-S
Don Clayton didn t like the idea of mixing of material from different zones on a molecular level and formation of carbonaceous grains from this mixture.
Ratio or Mass Fraction Ratio or Mass Fraction Si/S Ni O/Si O/Ne O/C He/C He/N H 1E+03 1E+02 1E+01 1E+00 1E-01 1E-02 1E-03 1E-04 1E-05 The He/N and He/C zones are the only zones with C>O. 1E-06 1E-07 1E+03 1E+02 1E+01 1E+00 1E-01 1E-02 1E-03 1E-04 1E-05 1E-06 1E-07 2 3 4 5 6 7 8 9 10 Interior Mass (M ) Ni Si/S O/Si 2.0 2.2 2.4 2.6 2.8 3.0 Interior Mass (M ) 12C/ 13 C/sol 14N/ 15 N/sol 26Al/ 27 Al 29Si/ 28 Si/sol 30Si/ 28 Si/sol 44Ti 49V C/O Deneault et al. proposed condensation of SiC in the region between 2.4 and 2.8 M interior mass of a 25 M SN.
One cannot reproduce the C-Si ratios in this way.
There are also problems with the Ti isotopic ratios.
In order to account for the isotopic signatures of outer SN zones ( 18 O, 26 Al, 13 C) Clayton proposed that during the passage of grains formed in the Si/S-O/Si zone through outer layers these grains collect tiny graphite grains that had previously formed in these layers.
16 O/ 18 O Ratio Image The interior has a larger 18 O excess than the outer regions. Low density graphite grain from Murchison separate KE3. Stadermann et al. (2005)
18 O Secondary electron and 18 O/ 16 O images obtained with the NanoSIMS from a microtome slice of a LD Orgueil grain.
15 N 18 O The 15 N and 18 O had to come from the He/C zone.
15 N 18 O An example from another LD Orgueil grain.
Ratio or Mass Fraction Higher mass SN models show a 15 N-rich spike in the He/N layer. 1E+03 SN-25-Rauscher O/C He/C He/N H 1E+02 1E+01 The correlation of 15 N with 18 O eliminates the possibility that 15 N excesses originate in the He/N zone. 1E+00 1E-01 1E-02 1E-03 1E-04 1E-05 1E-06 1E-07 12/13/sol 14/15/sol 26Al/27Al C/O 7 8 9 Interior Mass (M )
QuickTime and a decompressor are needed to see this picture. 18 O QuickTime and a decompressor are needed to see this picture. 15 N
CONCLUSION In some cases the grains isotopic ratios let us decide between different models (e.g., between 15 and 25 M models from C, N, O isotopes). In other cases the grain data do not agree with model predictions (Si, Si-S, Ti, Fe isotopes).