18-19 Settembre 2006

Dottorato in Astronomia Università di Bologna

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Hydrostatic equilibriumMass

continuity

Energy transport

Energy conservation

Chemical evolution

Stellar models: basic ingredients

An example: the pp chain

p+p D+e+

+ D+p 3He+

3He+4He 7Be+3He+3He 4He+2p

7Be+e- 7Li+7Li+p 4He+4He

7Be+p 8B+8B 8Be+e+

+8Be 4He+4He

CNO cycle

Moka Express 1933

Theory and its observational counterpart

5 MO

1 MO

Globular Clusters

pp-chain

CNO

3-

3-CNO

14N(p,)15O@LUNA

0E+00

2E+00

4E+00

6E+00

8E+00

1E+01

0 50 100 150 200 250 300 350 400

E (keV)

S-f

acto

r (k

eVb)

solid target tot

gas-target

MS

RG

B-A

GB

NO

VA

E

Io IAU general assembly. Chi sono H&R?

14N(p,)15O and the GC ages

S 14,1 /5

S 14,1 x5

Standard CF88

Depth of the convective envelopeas 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

3He-red

4He-blue

H-black

Salted envelope

C-red

N-blue

O-black

Initial abundance

1 M 3 M 5M

4He 0.280 0.301 0.295 0.2943He 3.54E-5 1.44E-3 1.70E-4 9.35E-512C 3.36E-3 2.93E-3 2.09E-3 2.11E-313C 4.04E-5 1.03E-4 1.03E-4 1.06E-414N 9.91E-4 1.42E-3 2.70E-3 2.78E-315N 3.90e-6 2.91e-6 1.86E-6 1.84e-616O 9.22E-3 9.22E-3 8.86E-3 8.75E-317O 3.73E-6 3.79E-6 3.86E-5 2.08E-518O 2.08E-5 2.00E-5 1.50E-5 1.51E-519F 4.90E-7 4.98E-7 4.72E-7 4.56E-7

3He crisis

Low mass stars synthesis

Clue for extramix ?

He ignition in degenerate core

The high densitydeveloped near the center induces the production of thermalneutrinos by plasma Oscillations and themaximumtemperature move off center

He-flashes

Central He-burning

4He

16O

12C

5 M

Z=0.02 Y=0.28

3 12C

12C+16

O+

Convective envelope

4He,14N

12C,16O

H5 M

Z=0.02 Y=0.28

Early-AGB: the second dredge up

Initial abundance

after

I du

after

II du

4He 0.280 0.294 0.328

3He 3.54E-5 9.35E-5 8.66E-5

12C 3.36E-3 2.11E-3 1.97E-313C 4.04E-5 1.06E-4 1.04E-4

14N 9.91E-4 2.78E-3 3.31E-3

15N 3.90e-6 1.84e-6 1.72E-6

16O 9.22E-3 8.75E-3 8.33E-3

17O 3.73E-6 2.08E-5 2.09E-518O 2.08E-5 1.51E-5 1.41E-5

19F 4.90E-7 4.56E-7 4.31E-7

The onset of the thermal pulses

Convective envelope

H-shell

He-shell CO 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-Burningluminosity

He-Burningluminosity

Thermal instability & nuclear runaway

Temperature evolution in the intershell zone

Nuclear energy production in theintershell zone

Third dredge up and 13C 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: 12C and s-elements.

13C pocket

time

M

TP

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 13C pocket is produced by the 12C+p reaction.

3) During the interpulse, the temperature in the pocket becomes larger than 90x106 K and neutrons are realized by the 13C+reaction.

Neutron sources: 22Ne(,n)25Mg

CNO 14N CNO-burning

14N(18F(18O(22Ne He-burning

T6>300

up to 1011 neutrons/cm3

Covective shell generated by a TP in IMS

PRIMARY

Neutron sources: 13C(,n)16O

Few protons injected into a C-rich zone

12C(p13N(13C

T6>100

106-107 neutrons/cm3

intershell zone during the interpulse in LMS & IMS

PRIMARY

The formation of the 13C pocket

In this model, an exponential decay of the convective velocity has been assumed below the convectively unstable zone.

H black

13C red 12C green

14N blue

The final fate:White Dwarf interior

High rate

12C()16O

Low rate

WD cooling & type Ia supernovae

high rate

low rate

BUM!!