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Supernovae continued

Supernovae continued

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Supernovae continued

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  1. Supernovae continued

  2. -rich Freezeout • Freezeout - nuclear reactions halted before coming to equilibrium or steady state configuration by temperature & density evolution • -rich freezeout occurs in material shocked to NSE temperatures. Expansion causes density to drop below critical value • Actually 2 freezeouts - 3 freezes out first due to 2 dependence, but  can still capture onto other nuclei to continue building heavier elements • For Ye = 0.5 get mostly 56Ni + free ’s. Main source of Ni to power light curve and 44Ti, which produces -rays when decaying to 44Ca which can map nucleosynthesis in young (few hundred years) remnants • May arise from Si or O shells

  3. -rich Freezeout

  4. -rich Freezeout T9=5.5, =6e7 T9=5.5, =5e7

  5. r-process • 1 second timescale - predicted by B2FH & Cameron. Neutron capture on seed nuclei faster than  decay timescale produces trans-Fe elements. Responsible for everything heavier than A=209 because of a gap instable nuclei above 209Bi. Also responsible for part of lower A nuclei. • Evidence for occurrence in SNe is circumstantial but probably correct • May occur in wind from proto-NS, convection of material into regions where  chemistry can increase , or convection into n-rich regions

  6. Yields • Fe produced during stellar lifetime in general does not escape in significant quantities - all ends up in compact remnant • Fe peak that gets out produced by explosive burning of Si & O. • Core collapse produces more intermediate mass  elements (O-Ti) relative to Fe than solar abundances • Populations enriched by CCSNe only (i.e. ones too young for SNIa to evolve) have high /Fe relative to solar.

  7. Yields • Important for anyone doing chemical evolution, stellar pops, etc. • Standard way of doing yields (i.e. Woosley & Weaver 95): Make a large grid of 1D models with several variable parameters & pick the linear combination of models which gives the desired abundance pattern, i.e. solar. Absolutely non-predictive • Six things than can change theoretical yields of 56Ni by up to 2 orders of magnitude: • Mechanism • Calculation method • Asymmetries/fallback • Nucleosynthesis calculation (network size, duration) • Progenitor structure • Explosion energy

  8. Yields • /Fe for local group globular clusters & dwarfs shows large spread for given [Fe/H]

  9. Yields • /Fe for local group globular clusters & dwarfs shows large spread for given [Fe/H]

  10. Yields • r process/s process for local group globular clusters & dwarfs shows large spread for given [Fe/H]

  11. Yields • /Fe for local group globular clusters & dwarfs shows large spread for given [Fe/H] • r process/s process for local group globular clusters & dwarfs shows large spread for given [Fe/H]

  12. Yields • 1foe vs. 2foe explosion below. Fe peak abundance change by orders of magnitude. 56Ni goes from 2e-16 to 0.3 M

  13. Supernova Classification • Observational classification from spectra & shape of lightcurve

  14. Supernova Classification • Type II SNe: Hydrogen present in early time spectrum. IIP have plateaus in lightcurve from large H envelopes. IIL have linear decays and small envelopes. Some transition to Ib spectra as H fades at late times. 87A is in this category. IIn have narrow lines, probably emitted from pre-SN mass loss at lower velocities.

  15. Supernova Classification • Type I SNe: No hydrogen present in early time spectrum. • Type Ia’s have broad Si lines. These are thermonuclear explosions of accreting white dwarfs, and are the most luminous, highest energy, and highest velocity SNe (except those associated with GRB’s??) • Type Ib’s don’t have strong Si lines. He is present. • Type 1c’s have no He. Ib/c’s are core collapse SNe that have lost their hydrogen (and He for Ic) envelopes prior to the supernova