Nuclear Astrophysics

1
Nuclear Astrophysics

• Roland Diehl
• Nuclear Astrophysics Science Issues
• Specific Sub-Topics Status, Challenges,
  Requirements
• Next Steps for Gamma-Ray Astronomy Missions

2
The Key Science Questions of Nuclear Astrophysics

• How are the elements and isotopes formed, which
  we see throughout the universe?
• How do nuclear transmutations affect the sites
  where they occur?

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Key Science Question 1 The Cosmic Abundance
Pattern

• How are the elements and isotopes formed, which
  we see throughout the universe?

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Key Science Question 1 (current-day frontier)
Cosmic Nuclear Reaction Dynamics

• How are the elements and isotopes formed, which
  we see throughout the universe?
• Nuclear-Reaction Dynamics
• Specific Isotopic Abundances as Calibration
  Marks

Cas A _at_ 1.157 MeV 44Ti (T1/259y)
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Key Science Question 2 (e.g.) Stellar
Evolution

• How do nuclear transmutations affect the sites
  where they occur?

Stars are gravitationally- confined
thermonuclear reactors Stellar structure lt-gt
Nuclear-reaction physics
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Key Science Question 2 (current-day frontier)
Cosmic Explosions

• How do nuclear transmutations affect the sites
  where they occur?

500 msec (fast!) R10000km)

• SNIa - HOW?
• Explosive C Burning
• Flame Propagation Dynamics
• Issues
• Rapid Time Scales
• Huge Range in Spatial Dimensions

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Key Science Question 1 The Present Status

• How are the elements and isotopes formed, which
  we see throughout the universe?
• Basics known (processes)
• Details poorly understood (e.g.)
• SNIa Fe yield 0.5 0.4 Mo
• Unknown sites for r-process(es), p nuclei
  synthesis
• Unknown relevant nuclear-reaction rates
• Uncertain relevance of neutrino reactions (ccSN)
• Stability of heavy nuclei (deformations, skin,?)
• Cosmic-ray nucleosynthesis (LiBeB) contribution
  uncertain

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Nuclear Reaction Uncertainties in Astrophysics

• New Effects
• EC in initial cc-SN n shells partly occupied
  at finite (SN) temperature

Experimentally-Unaccessible Reactions Target and
Projectile areRadioactive/shortlived
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Key Science Question 2 in Nuclear Astrophysics

• How do nuclear transmutations affect the sites
  where they occur?
• Basics known (stellar phases, explosions)
• Details poorly understood
• SNIa lightcurves vs. composition and GCE
• Shell burnings in massive stars and AGB
• Explosive C burning in SNIa
• Explosive shell burnings in SNII
• Burried C burning in Type-I XRB Superbursts

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Key Science Question 2 (current-day frontier)
Cosmic Explosions, Stars

• How do nuclear transmutations affect the sites
  where they occur?

• SNIa
• Nuclear-Burning Front
• CC-SN
• pe-gtn initial collapse
• Stars
• Stellar Core Sizes lt-gt
• 12C(a,g)16O

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Key Science Question 2 (current-day frontier)
Stellar Structure in Late Phases

• Episodes of Core and Shell Burning
• Impacts on Pre-SN Core Size Composition
• Nucleosynthesis Products

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Key Science Questions Interested?

• If we want to go beyond empirical models of the
  effects of
• Sources of nucleosynthesis -gt chemical
  evolution
• Stellar structure explosions -gt object/event
  frequencies
• then we need to proceed investigating the
  nuclear physics in cosmic environments
• MeV Gamma-rays are a natural messager
• (nuclear binding energies)

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Key Science Questions Relevant?

• If we want to go beyond current nuclear astronomy
  data of
• Gamma-ray observatories (survey _at_10-5 ph cm-2
  s-1 E/dE500)
• Indirect methods (e.g. inferred abundances from
  meteorites, recombination)
• then we must identify the uniqueness of cosmic
  gamma-rays in nuclear-astrophysics topics

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Cosmic Vision in Nuclear Astrophysics

• We seek understanding of cosmic phenomena in
  terms of nuclear-physics
• We want to add new qualities to existing astronomy

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Gamma-Ray Lines for Nucleosynthesis Study

• Radioactive Trace Isotopes as Nucleosynthesis
  By-Products
• For Gamma-Spectroscopy We Need
• Decay Time gt Source Dilution Time
• Yields gt Instrumental Sensitivities

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Status and Issues, in more detail

• Thermonuclear Supernovae (56Ni)
• Core Collapse Supernovae (56Ni, 44Ti)
• Novae (22Na, 7Be, e)
• Cumulative Nucleosynthesis
• Cosmological (56Ni)
• Massive Stars (26Al, 60Fe)
• Supernovae and Novae (e annihilation)

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Thermonuclear Supernovae (SNIa)

• Rarely SNIa 56Ni Decay Gamma-Rays are Above
  Instrumental Limits (10-5 ph cm-2 s-1)
• 2 Events captured / 9 Years CGRO
• Signal from SN1991T (3s) (13 Mpc)
• Upper Limit for SN1998bu (11 Mpc)
• 2 Candidate Events / 2 Years INTEGRAL
• Gamma-Ray Results
• Controversial
• Exceptional Events (1991T)?
• Systematic Uncertainty too Large!

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Thermonuclear Supernovae (SNIa)
Close Binary System
SN IaProgenitor Models
Giant
WD
White Dwarf Merger
Binary Mass Transfer
He Layer
C/O Layer

• Issues
• The 56Ni Power Source 0.5 Mo of 56Ni??
• Which Progenitor Path?
• Which Explosion Model?

WD at MCh
He Shell Flash
SN Ia
Central C Ignition
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Core Collapse-Supernovae Model
Empirical / Parametrized Models for
Explosion(Explosion Energy, Mass Cut)

• Explosion Mechanism Competition Between Infall
  and Neutrino Heating
• 3D-Effects Important for Energy Budget AND
  Nucleosynthesis

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Core Collapse Supernovae 56Ni and 44Ti

• Consistency of cc-SN Model Cas A vs.
• 44Ti from Models/SN1987A/g-Rays
• 44Ti Correlation to
• Large Explosion Energy
• Large Mass of 56Ni (Bright Supernova)

Aspherical explosions?? (-gtGRB) Need Event
Statistics, 44Ti Spectra
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Core Collapse Supernovae 60Fe

• Neutron Capture on 56,58Fe
• n Sources
• 13C(a,n)16O (He Burning)
• 20Ne(a,n)23Na (O/Ne Burning)
• Sites/Locations
• CC-Supernova O/Ne Shell and Bottom of He Shell
• Giant Phase of Massive Star He Shell, C Shell
• Astrophysical Significance
• Clarify SN Nuclear-Reaction Parameters
  (multi-paramter issue!)
• CC-SN Shell Structure
• n Capture from Fe-Group Elements-gt r-process
  feeding

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Novae

• Brief Annihilation Flash
• b Decay Continuum (before optical nova!)
• 22Na Radioactivity (O-Ne Novae)

• None SeenYet
• Need ltlt2kpc
• 511 keV Flash survey

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SNIa Cosmology with Gamma-Rays

• Cosmological SN Fill in MeV Emission to Diffuse
  Background (gap between AGN and Blazars SN
  lines redshift-gt characteristic cont)
• SN rate (zgt5), SNIa/cc-SN ratio (z SNIa delay)

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Massive Stars 26Al

• Nucleosynthesis in the Current Galaxy (t106y)
• Massive Stars are dominating sources
• COMPTEL imaging
• Massive-Star clusters of right age are
  26Al-bright
• Population synthesis
• Nucleosynthesis products from massive-star
  clusters ejected into ISM cavities
• COMPTEL Orion
• SPI Line Shapes
• Astronomical window to massive-star activity

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26Al Astronomy

• ISM Properties Near 26Al Sources
• 26Al Ejected into Hot Cavities (WR Winds, ) -gt
  ISM Turbulence lt-gt Line Width-gt 26Al Source
  Offset from Clusters
• 26Al Condensed on Dust, Re-accelerated -gt
  High-Velocity Tail?

Orion OB1 Plüschke et al. 2001

• Massive-Star Clusters
• Characteristic 26Al Lightcurve 3-7 My,
  WR-gtSNe-gt Cluster Ages

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Galactic Astronomy of 26Al Sources

• Galaxy Nearby Groups of Stars

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The 60Fe Puzzle
Model Predictions

• No Source Would Bring the 60Fe/26Al Gamma-Ray
  Intensity Ratio Close to Measurement Constraints!
  (Factor 5!)
• Nuclear Physics?
• Model Sample Statistics?

• Uncertainties
• n Capture Cross Sections for Fe Isotopes
• b Decay Rate for 59Fe
• Development of Hot-Base He Shell, C Shell
• n Source Activation

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Annihilation of Positrons in the Galaxy

• Positron-Source Variety
• Nucleosynthesis Sources (SNIa, )
• Pulsars, Binaries, Jet Sources
• Light Dark Matter Annihilations
• Annihilation in Diluted ISM (t105y)
• Status (INTEGRAL / SPI)
• Annihilation Rate (_at_GC) 1.4 1043 s-1
• Annihilation in Warm ISM Phase
• Extended 511 keV Line Emission
• Extended, bulge-like Emission (dl8o,db7o)
• Weak Disk Emission No Fountain
• -gt Young Stars make Minor Contribution
• Old stellar population!
• Dark-Matter Annihilations?

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Positron Annihilation Prospects

• After INTEGRAL
• Annihilation emission mapped throughout the
  Galaxy
• Inner-Galaxy 511 keV line shape well-measured
• Issues
• Other galaxies?
• Point sources?
• Specific regions with known sources?
• Dark matter constraints?

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Unique Nuclear-Astrophysics Info from Gamma-Rays

• SNIa
• Absolute Amount of 56Ni Radioactivity
• Progenitor Type
• Inner Explosion Kinematics
• CC-SNe
• Inner Core of SN Explosion (near mass cut)
• Shell Structure and Explosive Burning
• n Capture on Fe-Group Nuclei
• Novae
• Progenitor Evolution, Burning-Zone Mixing
• Cumulative Nucleosynthesis
• Cosmic SNIa Rate
• Massive-Star Group Nucleosynthesis
• ISM Around Massive Stars at 106y Time Scale
• Positron Transport in ISM/Galaxy

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Future Telescopes for Gamma-Ray Lines

• Advanced Compton Telescope
• Steve Boggs et al. -gt Elemental Origins Probe

• Laue Lens Photon Concentrator
• P. von Ballmoos et al. -gt MAX

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Instrumental Sensitivities for Gamma-Ray Lines
Advanced Compton Telescope
Courtesy S. Boggs, 2003
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Unique Nuclear-Astrophysics Info from Gamma-Rays

• SNIa
• Absolute Amount of 56Ni Radioactivity
• Progenitor Type
• Inner Explosion Kinematics
• CC-SNe
• Inner Core of SN Explosion (near mass cut)
• Shell Structure and Explosive Burning
• n Capture on Fe-Group Nuclei
• Novae
• Progenitor Evolution, Burning-Zone Mixing
• Cumulative Nucleosynthesis
• Cosmic SNIa Rate
• Massive-Star Group Nucleosynthesis
• ISM Around Massive Stars at 106y Time Scale
• Positron Transport in ISM/Galaxy

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Key Science in Nuclear Gamma-Ray Astrophysics

• Understand Supernova Explosions
• Exploit Line Astronomy in 26Al and e
  Annihilation

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Unique Nuclear-Astrophysics Info from Gamma-Rays

• SNIa
• Absolute Amount of 56Ni Radioactivity
• Progenitor Type
• Inner Explosion Kinematics
• CC-SNe
• Inner Core of SN Explosion (near mass cut)
• Shell Structure and Explosive Burning
• n Capture on Fe-Group Nuclei
• Novae
• Progenitor Evolution, Burning-Zone Mixing
• Cumulative Nucleosynthesis
• Cosmic SNIa Rate
• Massive-Star Group Nucleosynthesis
• ISM Around Massive Stars at 106y Time Scale
• Positron Transport in ISM/Galaxy

• ??