Prelim Review

1. Prelim Review

2. 9 7 8 6 5 10 1 4 3 2 <1.2 M

3. 9 7 8 6 5 10 1 4 3 2 <1.2 M • Hayashi track - fully convective cooler surface temp. requires super- sonic convection. Ends with burning of 2H • Star becomes radiative from core outward, becoming more compact & hotter. Occurs on thermal timescale Burn Li,Be,B at 1-2x106K - Li depletion happens when you  M ( Teff) because convective envelope is deeper, carries material to Li burning T. Higher M stars with shallower convective envelopes have more surface Li Late F stars also show Li depletion due to coupled rotational/wave mixing at base of shallow envelope

4. 9 7 8 6 5 10 1 4 3 2 <1.2 M 3. Bump from CN part of CNO cycle Convective core develops while C/N goes to equilibrium - short timescale after which L drops until PP takes over on main sequence 4. Main Sequence - PP chain dominates up to ~1.15 M no convective core since T dependence of PP (relatively) small, ~ T7 efficiency of H burning ~ 0.7%mc2, star burns ~10% of its mass ` Stars w/ radiative cores go up in L at ~ const Teff

5. 9 7 8 6 5 10 1 4 3 2 <1.2 M • Leaving main sequence - transition to shell H burning smooth because H still present at small r from center - inert core becomes degenerate As shell burns it gets thinner as T, get steeper - narrow shell has to support star against gravity of inert core - high L in shell which goes into mechanical work expanding star - as core contracts, envelope expands, moving star to red at ~ const L Shell burning lasts ~ 4 Gyr for sun before RGB

6. 9 7 8 6 5 10 1 4 3 2 <1.2 M • Red giant branch - star has moved as red as it can go - L of star now increases as convective envelope moves inward all the way to shell - R also increases He core is degenerate, L Mcore. First dredge-up mixes processed material to surface 7. Tip of the RGB - Core reaches ~ 0.45 M and T reaches He ignition (T~2e8) - Pdegeneracy not dependent on T, so no feedback like HSE - explosive burning & He flash. Star moves back down RGB as L goes into expanding core. Since L depends on core mass, and all stars must reach 0.45 M, tip of RGB at fixed luminosity (for given z) so acts as standard-ish candle.

7. 9 7 8 6 5 10 1 4 3 2 <1.2 M 8. Core He burning - 2(,)12C until YHe low, then 12C(,)16O takes over red clump coincides approximately with transition to 12C(,)16O. C/O decreases with stellar mass. 9. Asymptotic Giant Branch - He shell burning drives star back up parallel to but bluer than RGB. Star goes to much higher L. High mass loss rates from winds driven by line opacity, pulsations, & dust. Second dredge-up of nuclear processed material as convective envelope expands

8. 9 7 8 6 5 10 1 4 3 2 <1.2 M 10. Envelope lost through winds, late ejection possibly by flashes in degenerate shells. Evolution of PN central star more rapid for higher mass. End up w/ CO white dwarf with thin layers of He, H. Star very compact, high Teff, evolves ~ on lines of constant radius until crystallization. Stars low mass enough to make He white dwarfs haven’t evolved off MS. Only binaries w/ mass ejection make He WDs now. Solar mass star should make ~0.5 M WD distribution peaks at ~0.6.

9. 1.2-8 M 1-3. Similar to low mass stars. 4. Main Sequence: Stars above ~1.15 M dominated by CNO cycle H burning. T17 so all energy deposited in very small radius - convection necessary to transport energy. Convective core retreats as He increases (#e-/nucleon ), core also become more compact - star moves to red. Note: Mixing length gives wrong answers - based on thermodynamic instead of hydrodynamic stability. Waves and rotation also relevant to evolution

10. 1.2-8 M 5. H exhaustion: H depleted out to extent of convective core Star has to contract before T high enough where H remains for shell to ignite - star moves to blue briefly 6. H shell burning - no degeneracy in core over ~2.2 M so star crosses in Kelvin-Helmholtz time - Hertzsprung Gap 7a. For stars < ~2.2 M rest of evolution as for low mass 7b. As M , S, so  is lower for given T - no degeneracy before He ignition 8. As M  blue loops get bluer, so red clump turns into horizontal branch. Same for z

11. 1.2-8 M 9. Thermal Pulse AGB - He burns faster than H because of lower Q, catches up to & quenches H shell by . He shell runs out of fuel, H reignites & burns out until enough fuel for He - repeat from a few times for low masses to a few dozen times for high masses. Convective envelope gets deep during He phases - third dredge-up (actually many). Protons mixing with C-rich material generate neutrons. N capture on heavy seeds makes S process ~ 1/2 of material above Fe peak. Dredge-up gets s-process and C-rich material to surface - C/O > 1 at low metallicity 10. Intermediate mass stars produce CO white dwarfs with C/O <<1. Most massive may become ONeMg WD.

12. >8 M

13. >8 M 1-8. Very much the same as intermediate mass stars for masses < 30 M 9. Core evolution proceeds too quickly for TPAGB to develop. C ignition at T~6e8 K. Off-center degenerate C flash for lowest masses. Neutrino cooling dominates over photon cooling for T > 5e8 K. Burning must proceed at much larger rate so small fraction of energy in photons can provide pressure support. Evolution proceeds more rapidly than thermal adjustment timescale of star - not seen at surface.

14. >8 M 9a. C burning: T~6e8, 12C  20Ne, some 23,24Mg,23Na Ne burning: T~1e9, 20Ne  16O,some Mg,Si. Weak s-process in these stages O burning: T~2e9, 16O  32S at low T, 28Si at high T, some Mg,P, neutron fraction starts to increase - only shell O burning material get out Si burning: T>3e9, 28Si  Ca,Ti,Cr  Fe peak by -glomming. Neutron excess gets large. ~1.5 M of material processed in a few days - QSE and NSE dominate

15. >8 M 9a. Shell burning is highly dynamic process with significant asphericity, thermodynamic perturbations, & mixing. Shells are likely a single connected region at late stages with plumes burning in flashes determined by composition & T(r). Presupernova state will imprint substantially on explosion

16. Divergences at large M He burning begins earlier for higher M, lower z. Core He burning may begin early on Hertzsprung gap

17. Divergences at large M Above 30-35 M at solar z LBV eruptions & mass loss, mixing of He to surface force evolution to blue, eliminating red supergiant phases