1. L’evoluzione stellare: l’orologio
Evoluzione di stelle di massa piccola, intermedia e alta
Features sul HRD particolarmente importanti per il problema
Sistematica con la metallicita’
Caveats
June 2006
Lectures on Stellar Populations

2. Lectures on Stellar Populations
Evolutionary Tracks
1MO
2.5 MO
5 MO
20 MO
1 MO
100 MO
PAGB0.6 MO
To WD
ZAHB
ZAMS
RGB PN
Padova 94 set
Z=Zo Y=0.28
Lines of constant radii:
R=1,10,100,1000 Ro
R=0.008,0.013,0.014 Ro
(MWD=1,0.6,0.5 Mo)
Fagotto 94 Zsun tracks; solid are 0.6,0.8,1,2.2,2.5,5,20 and 100 Msun
PAGB tracks are dug out from UVdir
Purple lines are const R/Rsun of ,0.013 and 0.008, should become late evol. of 0.55,0.6 and 1 Msun
Dashed black lines are const R/Rsun of 1,10,100,1000
June 2006
Lectures on Stellar Populations

3. Lectures on Stellar Populations
RGB evolution
Back to HRD
RGB Bump
0.8 Mo
2 Mo
100Ro
10 Ro
Enlargement of low mass tracks (Fagotto 94, Zo) to show bump appearance and location
June 2006
Lectures on Stellar Populations

4. Lectures on Stellar Populations
Back to HRD
RGB : bump and LF
1.2 Mo
1 Mo
Sx: show why bump generates excess on LF.
Plotted here are: 1 and 1.2 Mo versus t/t_tip. Notice that bump does not occur at the same phase, but almost.
Dx: RGB LFs from synthetic tracks with Z= The RGB base masses are 1.127,1.365,1.47,1.796.
There would have been the with tau_tip=10 Gyr, but it was white and went off with bckg.
Notice shape of the LF, location of the bump..anticipate retreatment of TRGB.
June 2006
Lectures on Stellar Populations

5. Lectures on Stellar Populations
Flash and After
Back to HRD
M tr
RGB tip
RGB base
RGB tip
10 Ro
1 Ro
P-EAGB
100 Ro
0.03
0.07
0.12
Discuss concept of M_tr ; discuss L_tip as distance indicator: will be better illustrated later.
Dx: HB dispersion, and HB + E-AGB evolution.
Plotted tracks are (Zo): M= whose
Menv=
June 2006
Lectures on Stellar Populations

6. Lectures on Stellar Populations
Clump and Loops
Back to HRD
TRGB
ZAHB
2.2 Mo
9 Mo 4 7 6 5 3 15
10 Ro
Age indicator
Distance ind
Lmax,He
Lmin,He
June 2006
Lectures on Stellar Populations

7. Lectures on Stellar Populations
AGB Bump
BUMP
RGB
2.2 Mo
5 Mo
4 Mo
3 Mo
1 Mo with cost=-1
1.5 Mo with cost=-0.5
June 2006
Lectures on Stellar Populations

8. Lectures on Stellar Populations
Bump
Clump
PMS LF RGB HB AGB
June 2006
Lectures on Stellar Populations

9. A Field in the Halo of Centaurus A (Rejkuba et al 2005)
June 2006
Lectures on Stellar Populations

10. Lectures on Stellar Populations
First Pulse and TAGB
TAGB
Ist Pulse
TRGB
First Pulse luminosity and AGB tip: age indicators.
TAGB from bertelli isochs, with Zo. Depend on mass loss.
June 2006
Lectures on Stellar Populations

11. Lectures on Stellar Populations
Massive Stars
Evolution affected by MASS LOSS
OVERSHOOTING
First Pulse luminosity and AGB tip: age indicators.
TAGB from bertelli isochs, with Zo. Depend on mass loss.
Chiosi and Maeder 1986
June 2006
Lectures on Stellar Populations

12. Lectures on Stellar Populations
Back to HRD
Where the Stars are WR
C stars
Miras
Clump
Ceph HB
RRLyr WD
BSG
RSG
Dots are equally spaced in
There are 1000 dots along
each track
Would be nice to pop up P-L relations..next time
June 2006
Lectures on Stellar Populations

13. 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-AGB
Clumps
Nel diagramma di destra ci sono anche le tracce delle tre 0.9 masse
June 2006
Lectures on Stellar Populations

14. Evolutionary Lifetimes
tot MS
overshooting
RGB phase transition
rgb
He burning
Overshooting change of lambda at arounf 1.45 msun; transition at 1.9 – 2.2 Msun
June 2006
Lectures on Stellar Populations

15. Lectures on Stellar Populations
RGB Luminosities
Base
TIP
Notice behaviour at transition; notice Mtr and tau_tr
June 2006
Lectures on Stellar Populations

16. Helium Burning and beyond
Ist Pulse
He burn L-band
RGB trans
June 2006
Lectures on Stellar Populations

17. Isochrones Girardi et al. 2002
As Z increases:
isochrones get
fainter and redder
loops get shorter
WR stars are more
easily produced
June 2006
Lectures on Stellar Populations

18. 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 ..
Opacity:
affects MS width
occurrence and extension of loops
Blue to Red ratio
Mixing Length, rotation, diffusion, meridional circulation, nuclear reactions…
Separate dependence on Y and Z is important
June 2006
Lectures on Stellar Populations

19. Lectures on Stellar Populations
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
June 2006
Lectures on Stellar Populations