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HIGH ENERGY ASTROPHYSICS -ray emission from galactic radioactivity

HIGH ENERGY ASTROPHYSICS -ray emission from galactic radioactivity. Relevant radioactive nuclei for galactic -ray line emission : how and where they are synthesized: nucleosynthesis (hydrostatic and explosive), in stars interaction with cosmic rays, in the interstellar medium

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HIGH ENERGY ASTROPHYSICS -ray emission from galactic radioactivity

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  1. HIGH ENERGY ASTROPHYSICS-ray emission from galactic radioactivity • Relevant radioactive nuclei for galactic -ray line emission: • how and where they are synthesized: • nucleosynthesis (hydrostatic and explosive), in stars • interaction with cosmic rays, in the interstellar medium • Electron-positron annihilation emission (line and continuum): • e+ from +- unstable nuclei • BUT other sources of e+ ( radioactivity) exist • Type of emission: point-source or diffuse

  2. Radioactive decay and -ray line emission • Energy levels of atomic nuclei are spaced typically by ~ 1MeV • nuclear transitions involve absorption or emission of ’s • with E~1MeV • -ray line emission (with E ~1MeV) is expected from • nuclear deexcitation • Nuclear excitation occurs: • radioactive decay, either + (p n) or - (n p), and electron capture produce nuclei in excited states • collisions with energetic cosmic rays

  3. Radioactive decay and -ray line emission Q + decay: e+ emission X Y electron capture: no e+ emission

  4. Sites of explosive nucleosynthesis relevant for -ray line astronomy • SUPERNOVAE: • Thermonuclear supernovae (SN Ia): exploding white dwarfs in binary systems (no remnant) • Core collapse supernovae (SN II, SN Ib/c): exploding massive stars (M  10 M) (neutron star or black hole remnant) • v  104 km/s, E  1051 erg, Mej  M • CLASSICAL NOVAE: • Explosion of the external H-rich accreted shells of a white dwarf in a binary system • v  102 - 103 km/s, E  1045 erg, Mej  10-4 - 10-5M

  5. Radioactive isotopes relevant for -ray line astronomy Supernovae mainly Novae mainly e- capture +-

  6. Example: 56Ni • ~8.8 & 111.3 days detectable in individual sources very early after its synthesis: supernovae

  7. Radioactive isotopes relevant for -ray line astronomy Supernovae mainly Novae mainly e- capture +-

  8. Example: 57Ni • ~52h & 390 days detectable in individual sources very early after its synthesis: supernovae

  9. Radioactive isotopes relevant for -ray line astronomy Supernovae mainly Novae mainly e- capture +-

  10. Example: 44Ti Diehl & Timmes, 1998  ~89 yrs detectable in individual sources years after its synthesis: supernova remnants

  11. 44Ti halflive Weighted mean: t1/2=601 yrs (Motizuki et al. 2004)

  12. 56,57Ni and 44Ti production sites Explosive burning in massive stars (core collapse supernovae 56,57Ni and 44Ti are produced in the same internal zones details in SNe course Diehl & Timmes, 1998

  13. Radioactive isotopes relevant for -ray line astronomy Supernovae mainly Novae mainly e- capture +-

  14. Example: 26Al • ~106 yrs very difficult to detect in individual sources; cumulative effect; it samples ongoing nucleosynthesis in the Galaxy

  15. Example: 26Al nucleosynthesis path in novae José, Coc & Hernanz, 1999 details in Novae and Supernovae courses

  16. Radioactive isotopes relevant for -ray line astronomy Supernovae mainly Novae mainly e- capture +-

  17. Example: 60Fe Diehl & Timmes, 1998 • ~2x106 yrs very difficult to detect in individual sources; cumulative effect; it samples ongoing nucleosynthesis in the Galaxy

  18. 26Al and 60Fe production sites Massive stars: hydrostatic and explosive burning (H and O-Ne burning shells) 26Al and 60Fe are produced in similar regions and in comparable amounts details in SNe course Diehl & Timmes1998

  19. 26Al and 60Fe production sites Diehl & Timmes, 1998 Stars with M>25 M produce more 26Al than 60Fe

  20. Radioactive isotopes relevant for -ray line astronomy Supernovae mainly Novae mainly e- capture +-

  21. Example: 7Be Diehl & Timmes, 1998 • ~77 days detectable in individual sources, novae, shortly after the explosion; the cumulative effect of many novae may also be detectable, since  > t (between two succesive galactic novae) • details in Novae course • 7Li can also be a non nucleosynthetic product, but the result of energetic particle collisions (spallation reactions):  + 

  22. Example: 22Na Diehl & Timmes, 1998 • ~3.8 yrs detectable in individual sources, novae, shortly after the explosion; the cumulative effect of many novae may also be detectable, since  > t (between two succesive galactic novae) details in Novae course

  23. Observations of radioactivities

  24. Observations of radioactivities

  25. Observations of radioactivities

  26. Observations of radioactivities: Comptel instrument The Imaging Compton Telescope (COMPTEL) utilizes the Compton Effect and two layers of gamma-ray detectors to reconstruct an image of a gamma-ray source in the energy range 1 to 30 million electron volts (MeV). COMPTEL's upper layer of detectors are filled with a liquid scintillator which scatters an incoming gamma-ray photon according to the Compton Effect. This photon is then absorbed by NaI crystals in the lower detectors. The instrument records the time, location, and energy of the events in each layer of detectors which makes it possible to determine the direction and energy of the original gamma-ray photon and reconstruct an image and energy spectrum of the source.

  27. Observations of radioactivities: Comptel instrument The operating principle of COMPTEL. An incoming photon enters from above and Compton scatters in the first detection layer (blue), then is (partially) absorbed in the second layer (green).

  28. COMPTEL map of the 1.8 MeV line of 26Al Carina Vela Inner Galaxy Cygnus

  29. But 26Al was discovered in 1984, well before CGRO’s launch

  30. Observations of 26Al Reported 1.809 MeV fluxes for the inner Galaxy (Diehl & Timmes 1998)

  31. Diehl & Timmes 1998

  32. HEAO 3 line profile of the 1.8 MeV emission from 26Al(Mahoney et al 1984):FWHM<3keV

  33. GRIS (Ge detector on a balloon flight): line profile of the 1.8 MeV emission from 26Al(Naya et al 1996) FWHM=5.41.4keV v>500km/s; T>5x108K during 106 yrs!

  34. RHESSI (Ge detector): line profile of the 1.8 MeV emission from 26Al(Smith et al 2003): FWHM=21keV

  35. Observations of 26Al: comparison of line widths

  36. INTEGRAL/SPI observation of the 1.8 MeV line of 26Al Diehl et al. 2003 FWHM: 2.1-3.1keV; uncertainty: 0.7 keV

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