p-process signatures in presolar grains



Reto Trappitsch
October 18, 2024



A window into the past

  • Presolar grains are at least 4.567 Ga old
  • Interstellar residence time:

Biased sample since this was measured on very large grains!

p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Which type of star made these grains?

  • Most SiC grains from AGB stars
    • Condensed from convective envelope
    • Study the s-process
  • Some grains from core-collapse supernovae
    • Condensed in heterogeneous ejecta
    • Trace nucleosynthesis and the stellar engine
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Probing the p nuclei

  • Presolar CCSNe grains
    • Search for signatures of various nucleosynthesis processes
    • νp-process, ...
  • Presolar grains from AGB star
    • Majority of p nuclei are destroyed
    • Derive p abundance via precise s isotope measurements
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Probing the p nuclei

  • Presolar CCSNe grains
    • Search for signatures of various nucleosynthesis processes
    • νp-process, ...
  • Presolar grains from AGB star
    • Majority of p nuclei are destroyed
    • Derive p abundance via precise s isotope measurements
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024


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Separating isobars by laser ionization

p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Presolar CCSN grains: Ru, Mo, and Ba isotopes

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  • Very limited measurements for these grains are availasble
  • The p nuclei are often missing due to their low abundance
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

What can we do with these measurements?

  • Strange Mo isotopic pattern with enhancements in 96,97Mo
    • No p nuclei anomaly
    • Anomaly could be explained by neutrino driven winds (Bliss et al., 2018)
  • Ru isotopic pattern
    • Clear, correlated p and r nuclei enhancements
  • Contamination with solar material is a huge concern for these measurements

We need more correlated measurements to understand the underlying astrophysical processes

p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Mo in AGB star grains is especially interesting

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p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Peek inside an AGB star

  • s-process in He intershell
    → Destroys p nuclei
  • Dredge-up: Mix into convective envelope
  • Some p nuclei never see the s-process
    • Proxies for galactic chemical evolution
    • Determine abundance with precision measurements
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Measurements indicate constant r/p isotope production

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Stephan et al. (2019)
  • 92Mo not made in s-process but destroyed
  • Extrapolation towards no-92Mo yield pure s-process composition
  • This would be possible for other elements, e.g., Ru, Sm, and (maybe) Pt
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Varying stellar conditions

  • 97,98Mo constant
  • 94, 95, 100Mo vary more than expected
  • Variations likely indicate varying temperature/neutron density effects on branch points
p-process signatures in presolar grains | Oct 18, 2024

Remember the chart of the isotopes!

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p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Presolar grain analysis: Hands-on astrophysics...

  • Isotopic messenger
  • Fine probes for many processes
    • s-process nucleosynthesis
    • Rare nucleosynthesis processes
    • GCE
    • ...
  • High precision measurements allow us to understand rare astrophysical processes
  • Let's start with more comparisons of what we have measured!

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SiC grain imaged in the secondary electron microscope
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

... or astronomy with a microscope











xkcd.com
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024

Acknowledgement

Brett Isselhardt, Wei Jia Ong, Mike Savina, Ziva Shulaker
Andy Davis, Mike Pellin, Philipp Heck, Thomas Stephan
p-process signatures in presolar grains | Reto Trappitsch | Oct 18, 2024