18-19 Settembre 2006 Dottorato in Astronomia Universit di Bologna ? Hydrostatic equilibrium Mass continuity Energy transport Energy conservation Chemical evolution Stellar models: basic ingredients An example: the pp chain p+p D+e + + D+p 3 He+ 3 He+ 4 He 7 Be+ 3 He+ 3 He 4 He+2p 7 Be+e - 7 Li+ 7 Li+p 4 He+ 4 He 7 Be+p 8 B+ 8 B 8 Be+e Be 4 He+ 4 He CNO cycle Moka Express 1933 Theory and its observational counterpart 5 M O 1 M O Globular Clusters pp-chain CNO 3- 3- CNO 14 N(p, ) 15 MS RGB-AGB NOVAE I o IAU general assembly. Chi sono H&R? 14 N(p, ) 15 O and the GC ages S 14,1 /5 S 14,1 x5 Standard CF88 Depth of the convective envelope as a function of time Base of the convective envelope H-burning shell 1M Z=0.02 Globular Clusters luminosity function From: Rood et al 1999 ApJ 523, 572 1 M : chemical profiles 3 He-red 4 He-blue H-black Salted envelope C-red N-blue O-black Initial abundance 1 M 3 M 5M 4 He He3.54E-51.44E-31.70E-49.35E-5 12 C3.36E-32.93E-32.09E-32.11E-3 13 C4.04E-51.03E E-4 14 N9.91E-41.42E-32.70E-32.78E-3 15 N3.90e-62.91e-61.86E-61.84e-6 16 O9.22E E-38.75E-3 17 O3.73E-63.79E-63.86E-52.08E-5 18 O2.08E-52.00E-51.50E-51.51E-5 19 F4.90E-74.98E-74.72E-74.56E-7 3 He crisis Low mass stars synthesis Clue for extramix ? He ignition in degenerate core The high density developed near the center induces the production of thermal neutrinos by plasma Oscillations and the maximum temperature move off center He-flashes Central He-burning 4 He 16 O 12 C 5 M Z=0.02 Y= 12 C 12 C+ 16 O+ Convective envelope 4 He, 14 N 12 C, 16 O H 5 M Z=0.02 Y=0.28 Early-AGB: the second dredge up Initial abundance after I du after II du 4 He He3.54E-59.35E-58.66E-5 12 C3.36E-32.11E-31.97E-3 13 C4.04E-51.06E-41.04E-4 14 N9.91E-42.78E-33.31E-3 15 N3.90e-61.84e-61.72E-6 16 O9.22E-38.75E-38.33E-3 17 O3.73E-62.08E-52.09E-5 18 O2.08E-51.51E-51.41E-5 19 F4.90E-74.56E-74.31E-7 The onset of the thermal pulses Convective envelope H-shell He-shellCO core The E-AGB terminates when the H shell re- ignites, while the He shell dies down. When the mass of the intershell region exceeds a certain critical value, the He shell suffers a thermal instability. Evolution of TP stars: 5 M H-Burning luminosity He-Burning luminosity Thermal instability & nuclear runaway Temperature evolution in the intershell zone Nuclear energy production in the intershell zone Third dredge up and 13 C pocket After the thermal pulse the envelope expands and cools down. The H shell becomes inactive and the convective envelope can penetrate the H/He discontinuity, bringing to the surface the ashes of the He burning: 12 C and s-elements. 13 C pocket time M TP p Third dredge up 1)Few protons diffuse below the base of the convective envelope, where about 20% of the mass is made of carbon. 2)When the H shell re- ignites, a 13 C pocket is produced by the 12 C+p reaction. 3) During the interpulse, the temperature in the pocket becomes larger than 90x10 6 K and neutrons are realized by the 13 C+ reaction. Neutron sources: 22 Ne( ,n) 25 Mg CNO 14 N CNO-burning 14 N( 18 F( 18 O( 22 Ne He-burning T 6 >300 up to neutrons/cm3 Covective shell generated by a TP in IMS PRIMARY Neutron sources: 13 C( ,n) 16 O Few protons injected into a C-rich zone 12 C(p 13 N( 13 C T 6 > neutrons/cm3 intershell zone during the interpulse in LMS & IMS PRIMARY The formation of the 13 C pocket In this model, an exponential decay of the convective velocity has been assumed below the convectively unstable zone. H black 13 C red 12 C green 14 N blue The final fate: White Dwarf interior High rate 12 C( ) 16 O Low rate WD cooling & type Ia supernovae high rate low rate BUM!!