Evoluzione di stelle di massa piccola, intermedia e alta

1
Levoluzione stellare lorologio

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

2
Evolutionary Tracks

• Padova 94 set
• ZZo Y0.28

Lines of constant radii R1,10,100,1000
Ro R0.008,0.013,0.014 Ro (MWD1,0.6,0.5 Mo)
3
RGB evolution
Back to HRD
4
RGB bump and LF
Back to HRD
5
Flash and After
Back to HRD
6
Clump and Loops
Back to HRD
7
AGB Bump
8
PMS LFRGBHBAGB
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A Field in the Halo of Centaurus A(Rejkuba et al
2005)
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First Pulse and TAGB
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Massive Stars
Evolution affected by MASS LOSS
OVERSHOOTING
Chiosi and Maeder 1986
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Where the Stars are
Back to HRD
Dots are equally spaced in
There are 1000 dots along each track
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Dependence on Metallicity
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Evolutionary Lifetimes
15
RGB Luminosities
16
Helium Burning and beyond
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Isochrones Girardi et al. 2002

• As Z increases
• isochrones get
• fainter and redder
• loops get shorter
• WR stars are more
• easily produced

18
Uncertainties and wish list
Core Convection affects
stars 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
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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