Supernovae continued

-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

-rich Freezeout

-rich Freezeout

T9=5.5, =5e7 T9=5.5, =6e7

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

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.

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

Yields /Fe for local group globular

clusters & dwarfs shows large spread for given [Fe/H]

Yields /Fe for local group globular

clusters & dwarfs shows large spread for given [Fe/H]

Yields• r process/s process for local

group globular clusters & dwarfs shows large spread for given [Fe/H]

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]

Yields• 1foe vs. 2foe explosion below. Fe peak abundance change by

orders of magnitude. 56Ni goes from 2e-16 to 0.3 M

Supernova Classification• Observational classification from spectra & shape of lightcurve

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.

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