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The First Stars

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3 solar mass stars? Padoan et al (ApJ, 2007) find a primordial IMF clustered ... 'Standard model', 1.2 B, = 1.35, mix = 0.1, 10 - 100 solar masses ... – PowerPoint PPT presentation

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Title: The First Stars


1
Lecture 19 Pair Instability Supernovae and Popula
tion III
2
From the Big Bang
(The primordial abundance pattern) Brian Fields
(2002, priv. com.)
3
Today....
(The solar abundance pattern)
4
What were the properties of the first stars
to form after the Big Bang and what were their
nucleosynthetic and electro-magnetic
signatures?
5
Some calculations say the first generation
was very massive with typical masses of several
hundred solar masses z 15 to 30
Larson (2000) Bromm et al. (2000,2002) Abel et al
(2000,2002) Barkana and Loeb (2000) Bromm and
Larson (2004) Glover (2005) Ciardi and Ferrara
(2005) Ripomonte and Abel (2005) Yoshida et al
(2006) Oshea and Norman (2006) Gao et al (2007)
6
Uncertainties
  • Fragmentation, turbulence, magnetic fields
  • Radiative Truncation of accretion growth
  • Even if make 300 solar mass stars, do you
    also make 30 solar mass stars (McKee 2004)?
    3 solar mass stars?

Padoan et al (ApJ, 2007) find a primordial IMF
clustered around 10 solar masses. There may have
even been less very massive stars at high z. HD
more like Pop III
7
Padoan et al (ApJ, 2007) find a primordial IMF
clustered around 10 solar masses. There may have
even been less very massive stars at high z. HD
more like Pop III Were second generation Pop
III stars different from the First Stars?
8
Mass Loss in Very Massive Primordial Stars
  • Negligible line-driven winds (mass loss
    metallicity1/2)
  • No opacity-driven pulsations (no metals)
  • Continuum-driven winds not yet well
    understoodlikely very small contribution
  • Epsilon mechanism

Baraffe, Heger, and Woosley (ApJ, 2001)
9
The Epsilon Mechanism
  • Classical affects stars above 60MT
  • Reason high T-dependence of CNO cycle hydrogen
    burning (T18) at TCNO3107 K
  • Primordial Stars no initial CNO? contract till
    T108 K? produce CNO seeds (10-9)? CNO-H
    burning at T108 K? lower T-sensitivity (T14)?
    pulsational instability weaker

eT14
eT18
3107 K
10
Mass Loss in Very Massive Primordial Stars
  • Negligible line-driven winds (mass loss
    metallicity1/2) (Kudritzki 2002)
  • No opacity-driven pulsations (no metals)
  • Continuum-driven winds likely small contribution
  • Epsilon mechanism inefficient in metal-free stars
    below 1000 M? (Baraffe, Heger Woosley
    2000)from pulsational analysis we estimate upper
    limits
  • 120 solar masses lt 0.2
  • 300 solar masses lt 3.0
  • 500 solar masses lt 5.0
  • 1000 solar masses lt 12.0
  • during central hydrogen burning
  • Red Super Giant pulsations could lead to
    significant mass loss during helium burning for
    stars above 500 M?

11
Pair instability
Barkat, Rakavy and Sack (1967)
(M??gt 40 solar masses)
  • Helium core mostly convective and radiation a
    large part of the total pressure.??? 4/3.
    Contracts and heats up after helium burning.
    Ignites carbon burning radiatively
  • Above 1 x 109 K, pair neutrinos accelerate
    evolution. Contraction continues. Pair
    concentration increases. Energy goes into
    rest mass of pairs rather than increasing
    pressure, ? lt 4/3. Contraction accelerates.
  • Oxygen and (off-center) carbon burn explosively
    liberating a large amount of energy.
  • The star completely, or partially explodes

12
Nomoto and Hasimoto (1986)
Helium stars
13
Pair-Instability Supernovae
Many studies in literature since more than 3
decades, e.g., Rakavey, Shaviv, Zinamon
(1967) Bond, Anett, Carr (1984) Glatzel,
Fricke, El Eid (1985)Woosley (1986) Some
recent calculationsUmeda Nomoto 2001 Heger
Woosley 2002
Pulsational Pair Supernovae
Pair instability Supernovae
Rotation reduces these mass limits! Mass loss
alters them.
Black holes
14
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15
Ejected metals
16
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17
Elemental production factor in a 15 M? star
primordial initial composition
18
Elemental production factor in a 25 M? star
primordial initial composition
19
Elemental production factor in a 35 M? star
fallback
?
primordial initial composition
20
Production factor of massive Pop III stars
mixing included
21
Standard model, 1.2 B, ?? 1.35, mix 0.1, 10
- 100 solar masses
22
Best fit, 0.9 B, ?? 1.35, mix 0.0158, 10 - 100
solar masses
23
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24
(Christlieb)
25
Nucleosynthesis from Pair Instability Supernovae
Heger and Woosley (2002)
26
Initial mass 150M?
27
Initial mass 150M?
28
Initial mass 250M?
29
Initial mass 250M?
30
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31
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32
Production factor of massive and very massive Pop
III stars
33
  • Can very massive stars retain their mass
  • even today?
  • The Pistol Star
  • Galactic star
  • Extremely high mass loss rate
  • Initial mass 150 (?)
  • Will die as much less massive object

34
Eta Carina Thought to be over 100 solar
masses Giant eruption in 1843. Supernova-like
energy release. 2nd rightest star in the sky. V
-0.8 12 - 20 solar masses of material were
ejected in less than a decade. 8000 light years
distant. Doubled its brightness in 1998- 1999.
Now visble V 4.7.
35
238 million light years away
36
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37
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38
Woosley, Blinnikov and Heger (2007) Nature,
submitted
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