L’evoluzione stellare: l’orologio

June 2006 Lectures on Stellar Populations

• Evoluzione di stelle di massa piccola, intermedia e alta •Features sul HRD particolarmente importanti per il problema•Sistematica con la metallicita’•Caveats

L’evoluzione stellare: l’orologio


Evolutionary Tracks

Padova 94 set

Z=Zo Y=0.28

1MO

2.5 MO

2.5 MO

5 MO

20 MO

1 MO

100 MO

PAGB0.6 MO

2.5 MO

5 MO

To WD

ZAHB

ZAMS

RGB

PN

Lines of constant radii: R=1,10,100,1000 RoR=0.008,0.013,0.014 Ro (MWD=1,0.6,0.5 Mo)


RGB evolution

RGB Bump

0.8 Mo

2 Mo

100Ro

10 Ro

Back to HRD


RGB : bump and LFBack to HRD

1.2 Mo

1 Mo


Flash and After

M tr

RGB tip

RGB base

RGB tip

10 Ro1 Ro

P-EAGB

100 Ro

0.030.07

0.12

Back to HRD


Clump and LoopsBack to HRD

TRGB

ZAHB

2.2 Mo

9 Mo

4

7

6

5

3

15

10 Ro

Age indicator

Distan

ce

ind Lmax,He

Lmin,He


AGB Bump

2.2 Mo

5 Mo

4 Mo

3 Mo

1 Mo with cost=-1

1.5 Mo with cost=-0.5

BUMP

BUMP

RGB

RGB


PMS LF

RGB

HB

AGB

Bump

Clump

Bump

Bump

Clump


A Field in the Halo of Centaurus A(Rejkuba et al 2005)


First Pulse and TAGB

TAGB

Ist Pulse

TRGB


Massive Stars

Chiosi and Maeder 1986

Evolution affected by MASS LOSS OVERSHOOTING


Where the Stars are

WR

C stars

Miras

Clump

Ceph

HB

RRLyrWD

BSG

RSG

Back to HRD

Dots are equally spaced in

evol

There are 1000 dots alongeach track


Dependence on Metallicity

30 Mo

15 Mo

5 Mo

3 Mo

0.9 Mo

Clumps

0.5 Mo

0.55 Mo

0.6 Mo

AGB Manque’

Post E-AGBClumps


Evolutionary Lifetimes

tot

MS

overshooting

RGB phase transition

rgb

He burning


RGB Luminosities

Base

TIP


Helium Burning and beyond

Ist Pulse

He burn L-band

RGB trans


Isochrones Girardi et al. 2002

As Z increases:

• isochrones get fainter and redder

• loops get shorter

• WR stars are more easily produced


Uncertainties and wish list

Core Convection: affects star’s luminosity H and He lifetimes shape of tracks around Mhook

first H shell burning and runway for intermediate mass stars MS width location of RGB bump values of Mtr and Mup ratios N(HB)/N(AGB) loops extension Mass Loss: on the RGB affects Temperature extension of HB on the AGB affects value of Mup and TAGB for massive stars affects surface abundances, upper limit of Red SGs, productions of WR ..

Mixing Length, rotation, diffusion, meridional circulation, nuclear reactions…

Separate dependence on Y and Z is important

Opacity: affects MS width occurrence and extension of loops Blue to Red ratio


What have we learnt

To place on the HRD whatever mass at whatever age we want to pay attention to:

• Mtr Mup Mhook : lifetimes and tracks discontinuities

• Place correctly RGB Tip (as distance indicator)

• Describe accurately the evolution in core He burning close to RGB transition (Lum extension during evolution)

• Allow spread of envelope masses for HB stars

• Describe extension of the loops, location of BSG, Back-to-the-Blue evolution of high mass stars

• ………….

AND if we include a metallicity spread

Correctly describe all these systematics as a function of Metallicity

L’evoluzione stellare: l’orologio

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